You searched for +publisher:"Virginia Tech" +contributor:("Glasser, Wolfgang G.").
Showing records 1 – 30 of
30 total matches.
Virginia Tech
1.
Avellar, Brecc K.
Technical review and economic evaluation: steam- explosion/fractionation of biomass.
Degree: MS, Chemical Engineering, 1990, Virginia Tech
URL: http://hdl.handle.net/10919/41620 
► A series of process design and economics models have been created which calculate the process cost for several scenarios in steam-explosion/fractionation of wood. Steam…
(more)
▼ A series of process design and economics models have been created which calculate the
process cost for several scenarios in steam-explosion/fractionation of wood. Steam
-explosion pulping may prove to be an alternative to currently practiced standard pulping
processes which require large capital investments, cause significant environmental
problems, and produce a narrow range of products. In addition, steam-explosion/fractionation technology may offer the opportunity to produce chemicals and materials from
biomass at a lower raw material and process cost than the alternative petrochemical
feedstocks.
The models are a series of modular computer simulations, where each module summarizes
a particular group of unit operations with respect to mass balance, energy requirements,
and process cost including utilities, capital, labor, and other related costs. These modules
are compiled into 3 groups of scenarios: 1) unprocessed steam-exploded wood for use as
enzyme! acid hydrolysis feedstock, hardboard production, or as unbleached pulp, 2) water
extracted steam-exploded wood for recovery of pentosan polysaccharides and a
lignocellulosic fiber, and 3) water and aqueous solvent (alkali or ethanol) extracted steam
-exploded wood for recovery of pentosan polysaccharides, lignin polymers, and a cellulose
-rich, unbleached fiber.
For the base case evaluated, the cost of producing a 50% moisture, based on total weight,
steam-exploded fiber is the raw material cost, dry basis, plus 3.5 cents! Lb of raw material
consumed, dry basis. For Southwestern
Virginia hardwoods at 2 cents/Lb ($40 per ton),
dry basis, the total process cost is 5.5 cents/ Lb.
Advisors/Committee Members: Glasser, Wolfgang G. (committeechair), Michelsen, Donald L. (committee member), Velander, William H. (committee member).
Subjects/Keywords: Pulp mills; LD5655.V855 1990.A984
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Avellar, B. K. (1990). Technical review and economic evaluation: steam- explosion/fractionation of biomass. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/41620
Chicago Manual of Style (16th Edition):
Avellar, Brecc K. “Technical review and economic evaluation: steam- explosion/fractionation of biomass.” 1990. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/41620.
MLA Handbook (7th Edition):
Avellar, Brecc K. “Technical review and economic evaluation: steam- explosion/fractionation of biomass.” 1990. Web. 11 Apr 2021.
Vancouver:
Avellar BK. Technical review and economic evaluation: steam- explosion/fractionation of biomass. [Internet] [Masters thesis]. Virginia Tech; 1990. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/41620.
Council of Science Editors:
Avellar BK. Technical review and economic evaluation: steam- explosion/fractionation of biomass. [Masters Thesis]. Virginia Tech; 1990. Available from: http://hdl.handle.net/10919/41620
Virginia Tech
2.
Ibrahim, Mazlan.
Clean Fractionation of Biomass - Steam Explosion and Extraction.
Degree: MS, Wood Science and Forest Products, 1998, Virginia Tech
URL: http://hdl.handle.net/10919/36583
► The fractionation of two biomass resources, red oak (Quercus rubra) chips and oil palm (Elaeis guineensis) trunk solids, into constitutive chemical components, cellulose, hemicelluloses (called…
(more)
▼ The fractionation of two biomass resources, red oak (Quercus rubra) chips and oil palm (Elaeis guineensis) trunk solids, into constitutive chemical components, cellulose, hemicelluloses (called "other carbohydrates") and non-carbohydrates (includes lignin, tannins, etc.), was studied quantitatively in terms of relative cleanness. Red oak chips were steam exploded using a batch reactor at five different treatment severities, Ro 5,000, 10,000, 15,000, 20,000 and 35,000. Steam exploded fibers (SEF) of each severity were extracted with water and alkali. Mass fractionation and summative analysis data of all solid biomass fractions were determined. These data were interpreted in term of a unifying clean fractionation concept designed to evaluate the effectiveness of the fractionation processes. Within a series of severities applied to a single biomass resource, the quantitative clean fractionation can be used to choose an optimum severity for the isolation of any particular component fraction. The red oak results revealed that 25 % (on average) of biomass solids were lost during steam explosion. Cellulose remained almost unaffected (retained in fibers form) by water and alkali extraction. About 35-55 % of the hemicelluloses can be recovered in the water extracted liquor fraction (WEL). The remaining non-cellulosic carbohydrates were lost during steam explosion, especially at high severity. At Ro 10,000 and above, alkali extracted fibers (AEF) consists almost entirely of cellulose and non-carbohydrates. The majority of the non-carbohydrates component (> 50 %) can be isolated by alkali extraction. The non-carbohydrate component harvested increased with severity to 67% at Ro 35,000.
Advisors/Committee Members: Glasser, Wolfgang G. (committeechair), Helm, Richard F. (committee member), Agblevor, Foster Aryi (committee member).
Subjects/Keywords: Red oak (Quercus rubra); Oil palm (Elaeis guineensis); Hydrothermal process; Cellulose; Lignin; Hemicelluloses; Summative analysis.
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Ibrahim, M. (1998). Clean Fractionation of Biomass - Steam Explosion and Extraction. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/36583
Chicago Manual of Style (16th Edition):
Ibrahim, Mazlan. “Clean Fractionation of Biomass - Steam Explosion and Extraction.” 1998. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/36583.
MLA Handbook (7th Edition):
Ibrahim, Mazlan. “Clean Fractionation of Biomass - Steam Explosion and Extraction.” 1998. Web. 11 Apr 2021.
Vancouver:
Ibrahim M. Clean Fractionation of Biomass - Steam Explosion and Extraction. [Internet] [Masters thesis]. Virginia Tech; 1998. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/36583.
Council of Science Editors:
Ibrahim M. Clean Fractionation of Biomass - Steam Explosion and Extraction. [Masters Thesis]. Virginia Tech; 1998. Available from: http://hdl.handle.net/10919/36583
Virginia Tech
3.
Rauschenberg, Nancy Carol.
Thermoplastic xylan derivatives and related blends.
Degree: MS, Chemical Engineering, 1991, Virginia Tech
URL: http://hdl.handle.net/10919/41711
► The relationship between substituent chemistry and melt behavior for xylan derivatives was investigated by differential scanning calorimetry and parallel-plate dynamic viscometric measurements. Xylan esters exhibit…
(more)
▼ The relationship between substituent chemistry and melt behavior for xylan derivatives was investigated by differential scanning calorimetry and parallel-plate dynamic viscometric measurements. Xylan esters exhibit characteristic Tg values which decrease with increasing size of substituent. However, these materials do not flow at temperatures well above Tg. The ether derivative hydroxypropyl xylan was found to flow at substitution levels higher than 0.5 degree of substitution, with melt viscosity decreasing as the degree of substitution increased.
The influence of viscosity ratio and composition on the texture of melt-blends of hydroxypropyl cellulose and polystyrene was studied for viscosity ratios of 0.08 to 0.55. Blends were examined by SEM and TEM. It was found that composition was the determining factor in texture,
and not viscosity ratio over the range tested. Extrusion problems limited the range of compositions tested to 40% biopolymer or less. Phase inversion was not observed, although inversion was expected for some samples based on predictive models in the literature.
Advisors/Committee Members: Glasser, Wolfgang G. (committeechair), Baird, Donald G. (committee member), Wilkes, Garth L. (committee member).
Subjects/Keywords: Polysaccharides.; LD5655.V855 1991.R389
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Rauschenberg, N. C. (1991). Thermoplastic xylan derivatives and related blends. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/41711
Chicago Manual of Style (16th Edition):
Rauschenberg, Nancy Carol. “Thermoplastic xylan derivatives and related blends.” 1991. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/41711.
MLA Handbook (7th Edition):
Rauschenberg, Nancy Carol. “Thermoplastic xylan derivatives and related blends.” 1991. Web. 11 Apr 2021.
Vancouver:
Rauschenberg NC. Thermoplastic xylan derivatives and related blends. [Internet] [Masters thesis]. Virginia Tech; 1991. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/41711.
Council of Science Editors:
Rauschenberg NC. Thermoplastic xylan derivatives and related blends. [Masters Thesis]. Virginia Tech; 1991. Available from: http://hdl.handle.net/10919/41711
Virginia Tech
4.
Ghosh, Indrajit.
Blends of Biodegradable Thermoplastics With Lignin Esters.
Degree: MS, Wood Science and Forest Products, 1998, Virginia Tech
URL: http://hdl.handle.net/10919/36890
► Thermoplastic blends of several biodegradable polymers with lignin (L) and lignin esters were prepared by solvent casting and melt processing. Among the biodegradable thermoplastics were…
(more)
▼ Thermoplastic blends of several biodegradable polymers with lignin (L) and lignin esters were prepared by solvent casting and melt processing. Among the biodegradable thermoplastics were cellulose acetate butyrate (CAB), poly-hydroxybutyrate (PHB), poly-hydroxybutyrate-co-valerate (PHBV), and a starch-caprolactone blend (SCL). Lignin esters included acetate (LA), butyrate (LB), hexanoate (LH), and laurate (LL). Blend characteristics were analyzed in terms of thermal and mechanical properties. The results indicate widely different levels of interaction between two polymer constituents. Melt blended samples of CAB/LA and CAB/LB were compatible on a 15-30 nm scale when probed by dynamic mechanical thermal analysis, and the glass transition temperatures of the blends followed Fox equation, whereas those of CAB/LH and CAB/LL showed distinct broad transitions on the same scale. Melt blending produced well dispersed phases whereas large phase separation evolved out of solvent castings. Crystallinity and melting points of PHB and PHBV were affected by the incorporation of lignin component, revealing some interaction between the blend constituents. Blends of SCL with L and LB revealed significant effect on crystallinity and melting temperatures of poly-caprolactone component, revealing polymer-polymer interaction between SCL and lignin components. An increased degree of crystallinity was observed in the case of higher-Tg L compared to lower Tg LB. Improvememt in modulus (and in some cases strength also) was observed in almost all blends types due to the glassy reinforcing behavior of lignin.
Advisors/Committee Members: Glasser, Wolfgang G. (committeechair), Frazier, Charles E. (committee member), Davis, Richey M. (committee member).
Subjects/Keywords: starch; polycaprolactone; cellulose; ester; compatibility lignin; miscibility; blend; polymer; Biodegradable; polyhydroxybutyrate; cellulose acetate butyrate
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Ghosh, I. (1998). Blends of Biodegradable Thermoplastics With Lignin Esters. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/36890
Chicago Manual of Style (16th Edition):
Ghosh, Indrajit. “Blends of Biodegradable Thermoplastics With Lignin Esters.” 1998. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/36890.
MLA Handbook (7th Edition):
Ghosh, Indrajit. “Blends of Biodegradable Thermoplastics With Lignin Esters.” 1998. Web. 11 Apr 2021.
Vancouver:
Ghosh I. Blends of Biodegradable Thermoplastics With Lignin Esters. [Internet] [Masters thesis]. Virginia Tech; 1998. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/36890.
Council of Science Editors:
Ghosh I. Blends of Biodegradable Thermoplastics With Lignin Esters. [Masters Thesis]. Virginia Tech; 1998. Available from: http://hdl.handle.net/10919/36890
Virginia Tech
5.
Seavey, Kevin Christopher.
Lyocell Fiber-Reinforced Cellulose Ester Composites - Surface and Consolidation Considerations, and Properties.
Degree: MS, Wood Science and Forest Products, 1999, Virginia Tech
URL: http://hdl.handle.net/10919/35601
► The objective of this thesis was to further develop the polymer composite system consisting of cellulose acetate butyrate (CAB) and high modulus, continuous, regenerated cellulose…
(more)
▼ The objective of this thesis was to further develop the polymer composite system consisting of cellulose acetate butyrate (CAB) and high modulus, continuous, regenerated cellulose fiber (lyocell). Of particular concern were both the interfacial adhesion between the fiber and matrix and the consolidation process in the manufacture of these composite materials.
Interfacial adhesion was found to be substantial due to the relative lack of the fiber pull-out phenomenon observed after tensile failure in the unmodified fiber composites. This result was then supported in the second study in which similar unmodified fiber composites experienced very little fiber pull out with evidence of a large amount of cohesive failure of the matrix accompanied by matrix particles adhering to the fiber surfaces.
Void volume formation was mitigated to a small extent by the use of optimal consolidation conditions. Composites formed at moderate temperature (200 °C), low consolidation pressure (11.8 p.s.i.) and high consolidation time (13 min.) were found to have the lowest void volume formation of ca. 2.8 %. These composites were generally found to have the highest interfacial shear strength, ca. 16 MPa. A tensile modulus of 22 GPa and an ultimate strength of 246 MPa was obtained for this composite having a fiber volume content of ca. 62 %.
Advisors/Committee Members: Glasser, Wolfgang G. (committeechair), Davis, Richey M. (committee member), Kamke, Frederick A. (committee member).
Subjects/Keywords: Consolidation; Fiber Acetylation; Cellulosic Composites; Cellulose Acetate Butyrate
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Seavey, K. C. (1999). Lyocell Fiber-Reinforced Cellulose Ester Composites - Surface and Consolidation Considerations, and Properties. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35601
Chicago Manual of Style (16th Edition):
Seavey, Kevin Christopher. “Lyocell Fiber-Reinforced Cellulose Ester Composites - Surface and Consolidation Considerations, and Properties.” 1999. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/35601.
MLA Handbook (7th Edition):
Seavey, Kevin Christopher. “Lyocell Fiber-Reinforced Cellulose Ester Composites - Surface and Consolidation Considerations, and Properties.” 1999. Web. 11 Apr 2021.
Vancouver:
Seavey KC. Lyocell Fiber-Reinforced Cellulose Ester Composites - Surface and Consolidation Considerations, and Properties. [Internet] [Masters thesis]. Virginia Tech; 1999. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/35601.
Council of Science Editors:
Seavey KC. Lyocell Fiber-Reinforced Cellulose Ester Composites - Surface and Consolidation Considerations, and Properties. [Masters Thesis]. Virginia Tech; 1999. Available from: http://hdl.handle.net/10919/35601
Virginia Tech
6.
Johnson, Richard Kwesi.
Wetlaid Cellulose Fiber-Thermoplastic Hybrid Composites - Effects of Lyocell and Steam Exploded Wood Fiber Blends.
Degree: MS, Wood Science and Forest Products, 2004, Virginia Tech
URL: http://hdl.handle.net/10919/43767
► Fiber hybridization involves the blending of high and low performance fibers in a common matrix to yield a composite with a balance of properties that…
(more)
▼ Fiber hybridization involves the blending of high and low performance fibers in a common matrix to yield a composite with a balance of properties that cannot be achieved by using either fiber alone. In this study, the random wetlay process was used as a compounding method to investigate the effects of fiber hybridization on the mechanical, viscoelastic, and sorption characteristics of steam-exploded wood (SEW) and lyocell (high performance regenerated cellulose) fiber-reinforced polypropylene (PP) composites. The two fiber types were blended in varying proportions within a fixed total fiber content of 50 wt. % and compared with non-hybrid lyocell- and SEW-PP controls.
Using PP matrix as basis, it was observed that moduli of all composites generally increased with increasing lyocell concentration, ranging from a minimum 66 % for SP 50 (SEW/PP control) to a maximum 233 % for LP 50 (lyocell/PP control). Ultimate strengths on the other hand, declined for SP 50 but increased with the inclusion of lyocell fibers.
Comparisons of hybrid (having 5 - 20 wt % lyocell) with non-hybrid (having 25 - 50 wt. % lyocell) composites revealed a surprisingly greater strength and modulus-building efficiency (by as much as 2.6 times) in the hybrid composites. This observation indicated possible synergism between lyocell and SEW. Analyses of composite property gains as a function of fiber cost also showed greater cost benefits (highest for tensile modulus) in favor of hybridization.
The advantages of fiber hybridization on composite properties were again evident under dynamic mechanical analysis where no significant differences in the storage moduli were found between a hybrid composite with 20 wt. % lyocell and a non-hybrid composite with 50 wt. % lyocell loading. Application of the time-temperature superposition principle (TTSP) made it possible to predict storage moduli over extended frequencies for PP and its composites. Comparison of shift factor versus temperature plots revealed decreasing relaxation times of PP with increasing lyocell concentration, which indicated that PP interacted better with lyocell than with SEW fibers.
Finally, it was observed from sorption tests that hybrid composites absorbed less moisture than non-hybrid counterparts of either fiber type. The reasons for this observation were not apparent. It is however possible that moisture transport mechanisms within the composites may have been modified as a result of hybridization.
Advisors/Committee Members: Zink-Sharp, Audrey G. (committeechair), Frazier, Charles E. (committee member), Glasser, Wolfgang G. (committeecochair).
Subjects/Keywords: hybrid composites; viscoelastic properties; steam exploded wood; random wetlay process; sorption; lyocell; mechanical properties
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Johnson, R. K. (2004). Wetlaid Cellulose Fiber-Thermoplastic Hybrid Composites - Effects of Lyocell and Steam Exploded Wood Fiber Blends. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/43767
Chicago Manual of Style (16th Edition):
Johnson, Richard Kwesi. “Wetlaid Cellulose Fiber-Thermoplastic Hybrid Composites - Effects of Lyocell and Steam Exploded Wood Fiber Blends.” 2004. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/43767.
MLA Handbook (7th Edition):
Johnson, Richard Kwesi. “Wetlaid Cellulose Fiber-Thermoplastic Hybrid Composites - Effects of Lyocell and Steam Exploded Wood Fiber Blends.” 2004. Web. 11 Apr 2021.
Vancouver:
Johnson RK. Wetlaid Cellulose Fiber-Thermoplastic Hybrid Composites - Effects of Lyocell and Steam Exploded Wood Fiber Blends. [Internet] [Masters thesis]. Virginia Tech; 2004. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/43767.
Council of Science Editors:
Johnson RK. Wetlaid Cellulose Fiber-Thermoplastic Hybrid Composites - Effects of Lyocell and Steam Exploded Wood Fiber Blends. [Masters Thesis]. Virginia Tech; 2004. Available from: http://hdl.handle.net/10919/43767
Virginia Tech
7.
Eberhardt, Thomas Leonard.
Studies on lignin biosynthesis and structure.
Degree: MS, Forest Products, 1988, Virginia Tech
URL: http://hdl.handle.net/10919/42045
► Beech (Fagus grand1folia Ehrh.> bark contains appreciable quantities of Z- (cis) con1feryl and Z-s1napyl alcohols and not the corresponding E- (trans) alcohols. Previous rad1otracer…
(more)
▼ Beech (Fagus grand1folia Ehrh.> bark contains
appreciable quantities of Z- (cis) con1feryl and Z-s1napyl
alcohols and not the corresponding E- (trans) alcohols.
Previous rad1otracer experiments suggested that the
Z-coniferyl alcohol in beech bark is formed by isomerization
of E-coniferyl alcohol which proceeds either directly or
through the corresponding aldehydes. In the work
conducted in this thesis, is has been found that crude
cinnamy1 alcohol dehydrogenase isolated from beech bark shows
a strong substrate preference for E-coniferyl alcohol (as
opposed to Z-coniferyl alcohol) thereby suggesting that the E
to Z isomerization described occurs directly at the alcohol
level.
Administration of (2-
14C) ferul1c acid to feland wheat
(Triticum aest1yum L.) over extended durations (21 days) and
subsequent isolation of the lignin from the root tissue as
its acetal derivative demonstrated the incorporation of the
labelled feru1ic acid into the lignin component of the
tissue. Through sim1lar administrations of (1-
13C, 2-
13C and
3-
13C) ferul1c acid and subsequent analysis of the root
tissues by solid state
13C nuclear magnetic resonance (NMR)
spectroscopy, it was possible to determine the bonding
patterns of lignin in situ. The lignin component of each
13C
feru1ic acid enriched root tissue was then isolated as its
acetal derivative and analyzed by solution state
13C NMR.
Through comparison it was shown that the enhanced resonances
observed in the solution state
13C NMR spectra of the
13C
ferulic acid enriched acetal lignins corresponded to the
enhanced resonances in the respective spectra of the intact
root tissues. This indicated that minimal changes to the
lignin bonding patterns occurred during the isolation
procedure. The dominant presence of
13C NMR resonances
corresponding to hydroxycinnamic acid functionalities in the
solid and solution state NMR spectra demonstrates the
important role of hydroxyc1nnamic acids in wheat root lignin.
However, no evidence of the formation of dimers such as
4,4'-dihydroxytruxillic acid was noted. Thus, such
structures do not represent an important bonding pattern in
wheat root lignin.
Advisors/Committee Members: Lewis, Norman G. (committeechair), Ifju, Geza (committee member), Glasser, Wolfgang G. (committee member).
Subjects/Keywords: Lignin; LD5655.V855 1988.E347
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Eberhardt, T. L. (1988). Studies on lignin biosynthesis and structure. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/42045
Chicago Manual of Style (16th Edition):
Eberhardt, Thomas Leonard. “Studies on lignin biosynthesis and structure.” 1988. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/42045.
MLA Handbook (7th Edition):
Eberhardt, Thomas Leonard. “Studies on lignin biosynthesis and structure.” 1988. Web. 11 Apr 2021.
Vancouver:
Eberhardt TL. Studies on lignin biosynthesis and structure. [Internet] [Masters thesis]. Virginia Tech; 1988. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/42045.
Council of Science Editors:
Eberhardt TL. Studies on lignin biosynthesis and structure. [Masters Thesis]. Virginia Tech; 1988. Available from: http://hdl.handle.net/10919/42045
Virginia Tech
8.
Malmberg, Michael J.
Species Dependence of pMDI/Wood Adhesion.
Degree: MS, Wood Science and Forest Products, 2000, Virginia Tech
URL: http://hdl.handle.net/10919/9624
► Polymeric methylenebis(phenylisocyanate) (pMDI) has increasingly been used in the wood particulate composite industry. Wood composites, especially oriented strand board (OSB) are made with many variations…
(more)
▼ Polymeric methylenebis(phenylisocyanate) (pMDI) has increasingly been used in the wood particulate composite industry. Wood composites, especially oriented strand board (OSB) are made with many variations of wood species. Little research has been done to investigate how pMDI adhesion has been affected by species.
The present is divided into two parts. First, mode I fracture mechanics and surface free energy analysis was performed to investigate differences in adhesion between southern yellow pine and yellow-poplar bonded with pMDI. Secondly, an improvement in the synthesis of 13C, 15N labeled pMDI is discussed.
Mode I fracture results show that pMDI adhesion was affected differently by southern yellow pine compared yellow poplar. The shear energy release rate was significantly higher in pine/pMDI composites than in yellow poplar/pMDI composites. The total surface energy of southern yellow pine was shown to be significantly greater than yellow poplar. The free energy of adhesion (DG) of the pine/pMDI and the poplar/pMDI was investigated. The DG indicated that the pine/pMDI system would take more energy to separate compared to the poplar/pMDI system. Lastly, a double-labeled 13C, 15N pMDI adhesive was successfully synthesized to produce Solid-State NMR composites.
Advisors/Committee Members: Frazier, Charles E. (committeechair), Glasser, Wolfgang G. (committee member), Helm, Richard Frederick (committee member).
Subjects/Keywords: isocyanate; NMR; Fracture Mechanics; Wood Adhesion; FTIR
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Malmberg, M. J. (2000). Species Dependence of pMDI/Wood Adhesion. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/9624
Chicago Manual of Style (16th Edition):
Malmberg, Michael J. “Species Dependence of pMDI/Wood Adhesion.” 2000. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/9624.
MLA Handbook (7th Edition):
Malmberg, Michael J. “Species Dependence of pMDI/Wood Adhesion.” 2000. Web. 11 Apr 2021.
Vancouver:
Malmberg MJ. Species Dependence of pMDI/Wood Adhesion. [Internet] [Masters thesis]. Virginia Tech; 2000. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/9624.
Council of Science Editors:
Malmberg MJ. Species Dependence of pMDI/Wood Adhesion. [Masters Thesis]. Virginia Tech; 2000. Available from: http://hdl.handle.net/10919/9624
Virginia Tech
9.
Taib, Razaina Mat.
Cellulose fiber reinforced thermoplastic composites: Processing and Product Charateristics.
Degree: MS, Wood Science and Forest Products, 1998, Virginia Tech
URL: http://hdl.handle.net/10919/35428
► Steam exploded fibers from Yellow Poplar (Liriodendron tulipifera) wood were assessed in terms of (a) their impact on torque during melt processing of a thermoplastic…
(more)
▼ Steam exploded fibers from Yellow Poplar (Liriodendron tulipifera) wood were assessed in terms of (a) their impact on torque during melt processing of a thermoplastic cellulose ester (plasticized CAB); (b) their fiber incorporation and dispersion characteristics in a CAB-based composite by SEM and image analysis, respectively; and (c) their impact on the mechanical properties (under tension) of CAB-based composites having fiber contents of between 10 and 40% by weight. The fibers included water-washed steam exploded fibers (WEF), alkali-extracted fibers (AEF), acetylated fibers (AAEF), all from Yellow poplar (log Ro = 4.23), and oat fillers (COF) as control. The stepwise increase in cellulose content by extraction, and especially the (surface) modification by acetylation, contributed to increased torque during melt processing, and to improved interfacial adhesion as well as fiber dispersion. As compared to pure CAB, AAEF generated the highest increase in torque (+ 421%) followed by AEF (+ 260%) and WEF (+ 190%) at 40% fiber content by weight. AAEF was also found to enhance the tensile properties of the resulting composites. SEM studies of the tensile fracture surfaces indicated significant interfacial delamination and also pull - out of fibers when WEF, AEF, and COF were used to reinforce the CAB matrix. Composites with AAEF, by contrast, revealed fracture surfaces with reduced interfacial delamination and with significant fiber fracturing during failure. Image analysis was used to determine fiber dispersion within the resulting composites quantitatively. Significant improvement in fiber dispersion was achieved when the matrix was reinforced with acetylated fibers (AAEF). Fiber addition to the matrix resulted in loss of strain at break (- 80 to - 93%) and slight or significant increases in modulus (+ 47 to + 103%) depending on fiber type at 40% fiber content. Maximum stress declined for all fibers except AAEF at all fiber contents. AAEF-based composites revealed a decline in maximum stress when fiber content rose to 10%, and this reversed when fiber content increased beyond 10%. This increase in strength is consistent with the rule of mixtures that stipulates reinforcement of the matrix by fibers that are capable of transferring stresses across the fiber-matrix interface. All fibers suffered length decreases during melt processing.
Advisors/Committee Members: Glasser, Wolfgang G. (committeechair), Frazier, Charles E. (committee member), Kander, Ronald G. (committee member).
Subjects/Keywords: Steam-explosion treatment; acetylation; cellulose fiber; compounding; fiber dispersion
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Taib, R. M. (1998). Cellulose fiber reinforced thermoplastic composites: Processing and Product Charateristics. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35428
Chicago Manual of Style (16th Edition):
Taib, Razaina Mat. “Cellulose fiber reinforced thermoplastic composites: Processing and Product Charateristics.” 1998. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/35428.
MLA Handbook (7th Edition):
Taib, Razaina Mat. “Cellulose fiber reinforced thermoplastic composites: Processing and Product Charateristics.” 1998. Web. 11 Apr 2021.
Vancouver:
Taib RM. Cellulose fiber reinforced thermoplastic composites: Processing and Product Charateristics. [Internet] [Masters thesis]. Virginia Tech; 1998. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/35428.
Council of Science Editors:
Taib RM. Cellulose fiber reinforced thermoplastic composites: Processing and Product Charateristics. [Masters Thesis]. Virginia Tech; 1998. Available from: http://hdl.handle.net/10919/35428
Virginia Tech
10.
Barbero, Ana Maria.
Process and reactor design study of lignin propoxylation.
Degree: MS, Chemical Engineering, 1991, Virginia Tech
URL: http://hdl.handle.net/10919/44267
► Lignin, the second most abundant biopolymer on earth following cellulose, can be described as a million-ton, low cost, under-utilized resource. The use of lignin in…
(more)
▼ Lignin, the second most abundant biopolymer on earth following cellulose, can be described as a million-ton, low cost, under-utilized resource. The use of lignin in polymeric products adds the highest value to the raw material. Production of engineering plastics from lignin is an attractive approach to the utilization of lignin. The use of lignin in structural materials is limited by its
insolubility and its failure to undergo melt flow. A promising method to overcome the limitations is to chemically modify lignin by reaction with a low modulus substance, like an aliphatic ether. The reaction of lignin with propylene oxide (PO) produces a copolymer, hydroxypropyl lignin (HPL). Extensive studies have been directed toward the understanding of the chemistry and properties of HPL. A study of the process design is necessary to examine the economics of lignin propoxylation.
This work includes the chemical and kinetic analysis of the lignin propoxylation reaction as well as the modelling of a semibatch polymerization process; the design of a lignin propoxylation pilot plant; and a preliminary study of an industrial plant. Two models for the lignin propoxylation reaction are proposed and analyzed to produce a mathematical description of the reaction
process. The design of the pilot plant involves (a) the process design, which includes a material balance, a flow sheet, and a listing of the equipment; and (b) the economic analysis in which estimates of capital cost and operating costs are discussed. The scale-up to industrial production gives an estimate of the characteristics of a continuous process. This study constitutes a substantial contribution to the development of a new technology dealing with Engineering
Plastics from Lignin.
Advisors/Committee Members: Glasser, Wolfgang G. (committeechair), Michelsen, Donald L. (committee member), Velander, William H. (committee member).
Subjects/Keywords: Chemical reactors; LD5655.V855 1991.B372
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Barbero, A. M. (1991). Process and reactor design study of lignin propoxylation. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/44267
Chicago Manual of Style (16th Edition):
Barbero, Ana Maria. “Process and reactor design study of lignin propoxylation.” 1991. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/44267.
MLA Handbook (7th Edition):
Barbero, Ana Maria. “Process and reactor design study of lignin propoxylation.” 1991. Web. 11 Apr 2021.
Vancouver:
Barbero AM. Process and reactor design study of lignin propoxylation. [Internet] [Masters thesis]. Virginia Tech; 1991. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/44267.
Council of Science Editors:
Barbero AM. Process and reactor design study of lignin propoxylation. [Masters Thesis]. Virginia Tech; 1991. Available from: http://hdl.handle.net/10919/44267
Virginia Tech
11.
Ghosh, Indrajit.
Lyocell Fiber-Reinforced Cellulose Ester Composites-Manufacturing Considerations and Properties.
Degree: MS, Chemical Engineering, 1999, Virginia Tech
URL: http://hdl.handle.net/10919/35023
► Biodegradable thermoplastic composites were prepared using high modulus lyocell fibers and cellulose acetate butyrate (CAB). Two reinforcement fiber types: fabric and continuous fiber tow were…
(more)
▼ Biodegradable thermoplastic composites were prepared using high modulus lyocell fibers and cellulose acetate butyrate (CAB). Two reinforcement fiber types: fabric and continuous fiber tow were used. Fabric had advantages of uniform alignment and easier processing, but lacked the use as a unidirectional reinforcement and a continuous method of matrix application. Three different matrix application methods were screened for both fiber types. Matrix application by suspension of particles in water was not feasible because of particle sizes > 15 µ m. The other disadvantages were high moisture absorption during matrix application and void formation during consolidation. Melt processing technique using alternating sandwich structure of fabrics and CAB films produced composites with impressive appearance, low void contents and low moisture absorption. However, SEM results revealed interfacial failure and extensive fiber pull out. Relatively larger fiber and matrix regions were present on the scale of 10
-3m. Solution prepregging technique using methyl ethyl ketone (MEK) as a solvent for CAB and continuous fibers as reinforcement produced composites with uniform matrix distribution, high tensile strengths and high modulus, and even wetting of fibers by CAB. A maximum tensile modulus of 21.5 GPa and a maximum strength of 251.7 MPa were achieved for a continuous fiber reinforced composites at a volume fraction of 66.5% compared to 0.8 GPa and 76 MPa for the matrix, respectively. Void contents and water absorption were relatively high compared to comparable carbon fiber composites.
Advisors/Committee Members: Glasser, Wolfgang G. (committeechair), Frazier, Charles E. (committee member), Davis, Richey M. (committee member).
Subjects/Keywords: biodegradable composite; cellulose; cellulose ester; fiber; cellulose acetate butyrate; lyocell; solution prepregging; high modulus.; Composite
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Ghosh, I. (1999). Lyocell Fiber-Reinforced Cellulose Ester Composites-Manufacturing Considerations and Properties. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35023
Chicago Manual of Style (16th Edition):
Ghosh, Indrajit. “Lyocell Fiber-Reinforced Cellulose Ester Composites-Manufacturing Considerations and Properties.” 1999. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/35023.
MLA Handbook (7th Edition):
Ghosh, Indrajit. “Lyocell Fiber-Reinforced Cellulose Ester Composites-Manufacturing Considerations and Properties.” 1999. Web. 11 Apr 2021.
Vancouver:
Ghosh I. Lyocell Fiber-Reinforced Cellulose Ester Composites-Manufacturing Considerations and Properties. [Internet] [Masters thesis]. Virginia Tech; 1999. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/35023.
Council of Science Editors:
Ghosh I. Lyocell Fiber-Reinforced Cellulose Ester Composites-Manufacturing Considerations and Properties. [Masters Thesis]. Virginia Tech; 1999. Available from: http://hdl.handle.net/10919/35023
Virginia Tech
12.
Affleck, Richard Peter.
Recovery of Xylitol from Fermentation of Model Hemicellulose Hydrolysates Using Membrane Technology.
Degree: MS, Biological Systems Engineering, 2000, Virginia Tech
URL: http://hdl.handle.net/10919/30873
► Xylitol can be produced from xylose or hemicellulose hydrolysates by either chemical reduction or microbial fermentation. Current technology for commercial production is based on chemical…
(more)
▼ Xylitol can be produced from xylose or hemicellulose hydrolysates by either chemical reduction or microbial fermentation. Current technology for commercial production is based on chemical reduction of xylose or hemicellulose, and xylitol is separated and purified by chromatographic methods. The resultant product is very expensive because of the extensive purification procedures.
Microbial production of xylitol is being researched as an alternative method for xylitol production. Apart from the chromatographic separation method and activated carbon treatment, no other separation method has been proposed for the separation of xylitol from the fermentation broth.
Membrane separation was proposed as an alternative method for the recovery of xylitol from the fermentation broth because it has the potential for energy savings and higher purity. A membrane separation unit was designed, constructed, tested, and successfully used to separate xylitol from the fermentation broth. Eleven membranes were investigated for xylitol separation from the fermentation broth. A 10,000 nominal molecular weight cutoff (MWCO) polysulfone membrane was found to be the most effective for the separation and recovery of xylitol. The membrane allowed 82.2 to 90.3% of xylitol in the fermentation broth to pass through while retaining 49.2 to 53.6% of the Lowryâ s method positive material (such as oligopeptides and peptides). Permeate from the 10,000 MWCO membrane was collected and crystallized. Crystals were analyzed by HPLC for xylitol and impurities and determined to have purity up to 90.3%.
Advisors/Committee Members: Agblevor, Foster Aryi (committeechair), Cundiff, John S. (committee member), Chen, Jiann-Shin (committee member), Glasser, Wolfgang G. (committee member).
Subjects/Keywords: xylitol; reverse osmosis; ultrafiltration; nanofiltration; fermentation
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Affleck, R. P. (2000). Recovery of Xylitol from Fermentation of Model Hemicellulose Hydrolysates Using Membrane Technology. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/30873
Chicago Manual of Style (16th Edition):
Affleck, Richard Peter. “Recovery of Xylitol from Fermentation of Model Hemicellulose Hydrolysates Using Membrane Technology.” 2000. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/30873.
MLA Handbook (7th Edition):
Affleck, Richard Peter. “Recovery of Xylitol from Fermentation of Model Hemicellulose Hydrolysates Using Membrane Technology.” 2000. Web. 11 Apr 2021.
Vancouver:
Affleck RP. Recovery of Xylitol from Fermentation of Model Hemicellulose Hydrolysates Using Membrane Technology. [Internet] [Masters thesis]. Virginia Tech; 2000. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/30873.
Council of Science Editors:
Affleck RP. Recovery of Xylitol from Fermentation of Model Hemicellulose Hydrolysates Using Membrane Technology. [Masters Thesis]. Virginia Tech; 2000. Available from: http://hdl.handle.net/10919/30873
Virginia Tech
13.
Kaya, Abdulaziz.
Studies of polysaccharide adsorption onto model cellulose surfaces and self-assembled monolayers by surface plasmon resonance spectroscopy.
Degree: PhD, Chemistry, 2009, Virginia Tech
URL: http://hdl.handle.net/10919/39296
► Throughout the study of polymer adsorption at the air/water and solid/water interfaces, surface tension measurements and surface plasmon resonance (SPR) spectroscopy have been identified as…
(more)
▼ Throughout the study of polymer adsorption at the air/water and solid/water interfaces, surface tension measurements and surface plasmon resonance (SPR) spectroscopy have been identified as key methods for the acquisition of structural and thermodynamic information. These techniques were used to determine air/water and cellulose/water interfacial properties of pullulan (P) and pullulan cinnamates (PCs), 2-hydroxypropyltrimethylammonium xylans (HPMAXs), and hydroxypropyl xylans (HPXs).
Hydrophobic modification of pullulan with cinnamate groups promoted adsorption onto model surfaces of regenerated cellulose. In order to understand the relative contributions of hydrophilic and hydrophobic interactions towards PC adsorption, PC adsorption onto self-assembled monolayers (SAMs) with different functional groups was also studied. As the degree of cinnamate substitution increased, greater adsorption onto cellulose, methyl-terminated SAMs (SAM-CH3), and hydroxyl-terminated SAMs (SAM-OH) was observed. This study showed that hydrogen bonding alone could not provide a complete explanation for PC adsorption onto cellulose.
The adsorption of cationic 2-hydroxypropyltrimethylammonium (HPMA) xylans with different degrees of substitution (DS) onto SAMs and regenerated cellulose was studied by SPR. Surface concentration (Ð ) exhibited a maximum (Ð max) for HPMAX adsorption onto carboxylic acid-terminated SAMs (SAM-COOH) at an intermediate HPMA DS of 0.10. This observation was indicative of a relatively flat conformation for adsorbed HPMAXs with higher HPMA DS because of higher linear charge densities along the polymer backbone. Ð observed for HPMAX adsorption onto regenerated cellulose and SAM-OH surfaces was relatively low compared to HPMAX adsorption onto SAM-COOH surfaces.
Surface tension measurements for aqueous solutions of HPX by the Wilhelmy plate technique showed that surface tension changes ("γ = γwater " γHPX(aq)) increased and critical aggregation concentrations generally decreased with increasing hydroxypropyl (HP) DS. Hence, even though HP substitution was necessary to induce aqueous solubility, excessive hydroxypropylation promoted aggregation in water. SPR studies indicated that HPXs did not adsorb significantly onto regenerated cellulose or SAM-OH surfaces (submonolayer coverage). In contrast, HPX did adsorb (~monolayer coverage) onto SAM-CH3 surfaces.
Collectively, these studies showed natural polymers could be chemically modified to produce surface modifying agents with sufficient chemical control, whereby the surface properties of the resulting systems could be explained in terms of chemical structure and intermolecular interactions.
Advisors/Committee Members: Esker, Alan R. (committeechair), Madsen, Louis A. (committee member), Marand, Hervé L. (committee member), Glasser, Wolfgang G. (committee member), Ward, Thomas C. (committee member).
Subjects/Keywords: hemicelluloses; xylans; surface plasmon resonance spectroscopy; self-assembled monolayer; model cellulose surfaces; polysaccharide adsorption
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Kaya, A. (2009). Studies of polysaccharide adsorption onto model cellulose surfaces and self-assembled monolayers by surface plasmon resonance spectroscopy. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/39296
Chicago Manual of Style (16th Edition):
Kaya, Abdulaziz. “Studies of polysaccharide adsorption onto model cellulose surfaces and self-assembled monolayers by surface plasmon resonance spectroscopy.” 2009. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/39296.
MLA Handbook (7th Edition):
Kaya, Abdulaziz. “Studies of polysaccharide adsorption onto model cellulose surfaces and self-assembled monolayers by surface plasmon resonance spectroscopy.” 2009. Web. 11 Apr 2021.
Vancouver:
Kaya A. Studies of polysaccharide adsorption onto model cellulose surfaces and self-assembled monolayers by surface plasmon resonance spectroscopy. [Internet] [Doctoral dissertation]. Virginia Tech; 2009. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/39296.
Council of Science Editors:
Kaya A. Studies of polysaccharide adsorption onto model cellulose surfaces and self-assembled monolayers by surface plasmon resonance spectroscopy. [Doctoral Dissertation]. Virginia Tech; 2009. Available from: http://hdl.handle.net/10919/39296
Virginia Tech
14.
Laborie, Marie-Pierre Genevieve.
Investigation of the Wood/Phenol-Formaldehyde Adhesive Interphase Morphology.
Degree: PhD, Wood Science and Forest Products, 2002, Virginia Tech
URL: http://hdl.handle.net/10919/26411
► This work addresses the morphology of the wood/ Phenol-Formaldehyde (PF) adhesive interphase using yellow-poplar. In this case, morphology refers to the scale or dimension of…
(more)
▼ This work addresses the morphology of the wood/ Phenol-Formaldehyde (PF) adhesive interphase using yellow-poplar. In this case, morphology refers to the scale or dimension of adhesive penetration into wood. The objective is to develop methods for revealing ever smaller levels of wood/resin morphology. Dynamic techniques that are commonly utilized in polymer blend studies are investigated as potential methods for probing the wood/ adhesive interphase morphology. These are Dynamic Mechanical Analysis (DMA) and solid state NMR using CP/MAS. PF resin molecular weight is manipulated to promote or inhibit resin penetration in wood, using a very low or a very high molecular weight PF resin.
With DMA, the influence of PF resin on wood softening is investigated. It is first demonstrated that the cooperativity analysis according to the Ngai coupling model of relaxation successfully applies to the in-situ lignin glass transition of yellow-poplar and spruce woods. No significant difference in intermolecular coupling is detected between the two woods.
It is then demonstrated that combining simple DMA measurements with the cooperativity analysis yields ample sensitivity to the interphase morphology. From simple DMA temperature scans, a low molecular weight PF (PF-Low) does not influence lignin glass transition temperature. However, the Ngai coupling model of relaxation indicates that intermolecular coupling is enhanced with the low molecular weight PF. This behavior is ascribed to the low molecular weight PF penetrating lignin on a nanometer scale and polymerizing in-situ.
On the other hand, a high molecular weight resin with a broad distribution of olecular weights (PF-High) lowers lignin glass transition temperature dramatically. This plasticizing effect is ascribed to a small fraction of the PF resin being low enough in molecular weight to penetrate lignin on a nanoscale, but being too dispersed for forming a crosslinked network.
With CP/MAS NMR, intermolecular cross-polarization experiments are found unsuitable to probe the angstrom scale morphology of the wood adhesive interphase. However, observing the influence of the PF resins on the spin lattice relaxation time in the rotating frame, HT1r, and the cross-polarization time (TCH) is useful for probing the interphase morphology. None of the resins significantly affects the cross-polarization time, suggesting that angstrom scale penetration does not occur with a low nor a high molecular weight PF resin. However, the low molecular weight PF substantially modifies wood polymer HT1r, indicating that the nanometer scale environment of wood polymers is altered. On the other hand, the high molecular weight PF resin has no effect on wood HT1r. On average, the high molecular weight PF does not penetrate wood on a nanometer scale. Interestingly, the low molecular weight PF resin disrupts the spin coupling that is typical among wood components. Spin coupling between wood components is insensitive to the high molecular weight PF. Finally, it is noteworthy that…
Advisors/Committee Members: Frazier, Charles E. (committeechair), Glasser, Wolfgang G. (committee member), Kamke, Frederick A. (committee member), Esker, Alan R. (committee member), Ward, Thomas C. (committee member), Marand, Eva (committee member).
Subjects/Keywords: cooperativity analysis of wood; solid-state NMR; glass transition; wood/adhesive interphase
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Laborie, M. G. (2002). Investigation of the Wood/Phenol-Formaldehyde Adhesive Interphase Morphology. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/26411
Chicago Manual of Style (16th Edition):
Laborie, Marie-Pierre Genevieve. “Investigation of the Wood/Phenol-Formaldehyde Adhesive Interphase Morphology.” 2002. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/26411.
MLA Handbook (7th Edition):
Laborie, Marie-Pierre Genevieve. “Investigation of the Wood/Phenol-Formaldehyde Adhesive Interphase Morphology.” 2002. Web. 11 Apr 2021.
Vancouver:
Laborie MG. Investigation of the Wood/Phenol-Formaldehyde Adhesive Interphase Morphology. [Internet] [Doctoral dissertation]. Virginia Tech; 2002. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/26411.
Council of Science Editors:
Laborie MG. Investigation of the Wood/Phenol-Formaldehyde Adhesive Interphase Morphology. [Doctoral Dissertation]. Virginia Tech; 2002. Available from: http://hdl.handle.net/10919/26411
Virginia Tech
15.
Kumar, Guneet.
Design of anion exchange cellulose hydrogel for large proteins.
Degree: PhD, Chemical Engineering, 1994, Virginia Tech
URL: http://hdl.handle.net/10919/38250
► In our previous studies, uncross-linked large diameter cellulose beads were optimized for solids content, bead size, pressure-flow limits, molecular accessibility and performance as an immunosorbent.…
(more)
▼ In our previous studies, uncross-linked large diameter cellulose beads were optimized for solids content, bead size, pressure-flow limits, molecular accessibility and performance as an immunosorbent. Here, anion exchange (DEAE) cellulose beads were derivatized by two different procedures (defined as A and B) and the changes in bead morphology were correlated with transport and sorption kinetics. The kinetic characteristics clearly defined a minimum of two different types of protein binding site architecture. DEAE cellulose beads exhibited molecular exclusion of BSA near the edge of the bead in contrast to greater permeability seen in underivatized beads. Thus, accessible BSA binding sites are present only on the surface of the derivatized beads. DEAE cellulose beads derivatized by procedure B gave higher density of DEAE ligand as compared to beads derivatized by procedure A, as well as higher static and dynamic capacity for BSA. Even though DEAE cellulose beads (DP 2070, 450 μm diameter derivatized by procedure B) have lower small ion capacity than DEAE cross-linked agarose beads, as well as 1/4 the surface area, they exhibit equivalent binding capacity for BSA per volume of support. Thus, DEAE cellulose beads possess more sites per surface area as well as have lower ligand density per BSA site. Furthermore, BSA adsorption sites on DEAE cellulose beads derivatized by procedure B exhibit slow binding kinetics as compared to those derivatized by procedure A and also compared to DEAE crosslinked agarose beads. Thus, the rate limiting step for the adsorption of BSA on DEAE cellulose beads was not diffusion as suggested by the large diameter of the bead. Feasibility studies were performed for process scale applications to fixed and expanded bed anion exchange purification. The large diameter DEAE cellulose beads of this study maybe useful for process scale anion exchange as evident from purification of immunoglobulins from hybridoma cell culture in fixed bed. The balance of large diameter and density of these DEAE cellulose beads enable stable expanded bed purification of proteins such as recombinant human protein C from transgenic porcine whey.
Advisors/Committee Members: Velander, William H. (committeechair), Davis, Richey M. (committee member), Conger, William L. (committee member), Glasser, Wolfgang G. (committee member), McNair, Harold M. (committee member).
Subjects/Keywords: Ion exchange chromatography; LD5655.V856 1994.K863
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Kumar, G. (1994). Design of anion exchange cellulose hydrogel for large proteins. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/38250
Chicago Manual of Style (16th Edition):
Kumar, Guneet. “Design of anion exchange cellulose hydrogel for large proteins.” 1994. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/38250.
MLA Handbook (7th Edition):
Kumar, Guneet. “Design of anion exchange cellulose hydrogel for large proteins.” 1994. Web. 11 Apr 2021.
Vancouver:
Kumar G. Design of anion exchange cellulose hydrogel for large proteins. [Internet] [Doctoral dissertation]. Virginia Tech; 1994. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/38250.
Council of Science Editors:
Kumar G. Design of anion exchange cellulose hydrogel for large proteins. [Doctoral Dissertation]. Virginia Tech; 1994. Available from: http://hdl.handle.net/10919/38250
Virginia Tech
16.
Becker, Ulrike.
Smart Surfaces in Biobased Materials.
Degree: PhD, Wood Science and Forest Products, 1998, Virginia Tech
URL: http://hdl.handle.net/10919/30714
► The self-assembly blends of cellulose propionate (CP) and fluorine (F)-containing cellulose derivatives was examined on a model system of solvent cast films. The F-containing derivatives…
(more)
▼ The self-assembly blends of cellulose propionate (CP) and fluorine (F)-containing cellulose derivatives was examined on a model system of solvent cast films. The F-containing derivatives were either high molecular weight statistical cellulose esters with a number of F-containing substituent evenly distributed along the backbone (F-esters), or F-terminated CP-segments with exactly one F-containing endgroup. The F-esters were synthesized in a homogeneous phase and identified by 19F-NMR. Thermal analysis showed improved thermal stability of the F-esters when compared to F-free derivatives.
1-monohydroxy functionalized CP-segments were synthesized by HBr depolymerization using either a commercially available CP with residual OH-groups or a perpropionylated CP (CTP). The hydrolysis using the commercial CP yielded only segments of a minimum DP of 50 and the Mark-Houwink constant declined from 1 to 0.6. The results indicate that in the presence of free hydroxyls branches are formed by transglycosidation. The hydrolysis from perpropionylated CP resulted in segments with a minimum DP of 7, which is in accordance to previous studies.
F-terminated CP segments were synthesized by coupling of the appropriate F-containing alcohol to the CP segment via toluene diisocyanate.
Solutions containing F-terminated CP-segments showed typical critical micelle behavior. The critical micelle concentration depended on the molecular weight of the CP segment and the type of F-containing endgroup. The micelles are thought to consist of a core of the F-endgroups and a corona made-up of CP. Films containing the oligomers cast from micellar solution revealed a linear decrease in wetting force according to the blend composition of the oligomer, i.e. behavior according to the rule of mixing. This indicated the absence of surface segregation of the F-endgroup and it is explained with the fact that the micellar structure is retained in the solid state, suppressing surface segregation. The solid state micelles were visualized as dome-like protrusions by height image atomic force microscopy. In systems blended with CP the distance between the protrusions was found to increase with increasing CP content which was explained by a dilution process.
Films containing F-esters were characterized by wetting force measurements and x-ray photoelectron spectroscopy (XPS). The wetting force decreased dramatically at low blend content of the F-ester and at the same time an F surface-concentration higher then expected from the blend composition was found by XPS. This indicated self-assembly by surface segregation of the F-containing species during film formation. The extent of surface segregation was found to depend on the type of the F-ester group as well as on the blend concentration of the F-ester.
Dynamic wetting force measurements revealed hysteresis in films containing either F-esters or F-terminated CP segments. The hysteresis was found to be both kinetic (water sorption and reorganization) and thermodynamic (surface roughness and surface coverage with…
Advisors/Committee Members: Glasser, Wolfgang G. (committeechair), Frazier, Charles E. (committee member), Wightman, James P. (committee member), Wilkes, Garth L. (committee member), Davis, Richey M. (committee member).
Subjects/Keywords: cellulose propionate; surface analysis; surface segregation; reorganization; XPS; AFM
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Becker, U. (1998). Smart Surfaces in Biobased Materials. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/30714
Chicago Manual of Style (16th Edition):
Becker, Ulrike. “Smart Surfaces in Biobased Materials.” 1998. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/30714.
MLA Handbook (7th Edition):
Becker, Ulrike. “Smart Surfaces in Biobased Materials.” 1998. Web. 11 Apr 2021.
Vancouver:
Becker U. Smart Surfaces in Biobased Materials. [Internet] [Doctoral dissertation]. Virginia Tech; 1998. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/30714.
Council of Science Editors:
Becker U. Smart Surfaces in Biobased Materials. [Doctoral Dissertation]. Virginia Tech; 1998. Available from: http://hdl.handle.net/10919/30714
Virginia Tech
17.
Sernek, Milan.
Comparative Analysis of Inactivated Wood Surfaces.
Degree: PhD, Wood Science and Forest Products, 2002, Virginia Tech
URL: http://hdl.handle.net/10919/27429
► A wood surface, which is exposed to a high temperature condition, can experience inactivation. Surface inactivation results in reduced ability of an adhesive to properly…
(more)
▼ A wood surface, which is exposed to a high temperature condition, can experience inactivation. Surface inactivation results in reduced ability of an adhesive to properly wet, flow, penetrate, and cure. Thus, an inactivated wood surface does not bond well with adhesives.
The changes in surface chemistry, wettability, and adhesion of inactivated wood surfaces, including heartwood of yellow-poplar (Liriodendron tulipifera) and southern pine (Pinus taeda), were studied. Wood samples were dried from the green moisture content condition in a convection oven at five different temperature levels ranging from 50 to 200 °C. The comparative characterization of the surface was done by X-ray photoelectron spectroscopy (XPS), sessile drop wettability, and fracture testing of adhesive bonds.
The oxygen to carbon ratio (O/C) decreased and the C1/C2 ratio increased with drying temperature. The C1 component is related to carbon-carbon or carbon-hydrogen bonds, and the C2 component represents single carbon-oxygen bond. A low O/C ratio and a high C1/C2 ratio reflected a high concentration of non-polar wood components (extractives/VOCs) on the wood surface, which modified the wood surface from hydrophilic to more hydrophobic. Wettability was directly related to the O/C ratio and inversely related to the C1/C2 ratio. Contact angle decreased with time and increased with the temperature of exposure. Southern pine had a lower wettability than yellow-poplar, which was due to a greater concentration of non-polar hydrocarbon-type extractives and heat-generated volatiles on the surface. Solvent extraction prior to drying did not improved wettability, whereas, extraction after drying improved wettability. A contribution of extractives migration and VOCs generation played a significant role in the heat-induced inactivation process of southern pine.
The maximum strain energy release rate (Gmax) showed that surface inactivation was insignificant for yellow-poplar when exposed to drying temperatures < 187°C. The southern pine was most susceptible to inactivation at drying temperatures > 156°C, particularly when bonded with phenol-formaldehyde (PF) adhesive. Chemical treatments improved the wettability of inactivated wood surfaces, but an improvement in adhesion was not evident for specimens bonded with polyvinyl-acetate (PVA) adhesive. NaOH surface treatment was most effective for improving adhesion of the PF adhesive bond.
Advisors/Committee Members: Frazier, Charles E. (committee member), Dillard, John G. (committee member), Helm, Richard F. (committee member), Kamke, Frederick A. (committeecochair), Glasser, Wolfgang G. (committeecochair).
Subjects/Keywords: XPS; Adhesion; Wettability; Wood Surface Inactivation
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Sernek, M. (2002). Comparative Analysis of Inactivated Wood Surfaces. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/27429
Chicago Manual of Style (16th Edition):
Sernek, Milan. “Comparative Analysis of Inactivated Wood Surfaces.” 2002. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/27429.
MLA Handbook (7th Edition):
Sernek, Milan. “Comparative Analysis of Inactivated Wood Surfaces.” 2002. Web. 11 Apr 2021.
Vancouver:
Sernek M. Comparative Analysis of Inactivated Wood Surfaces. [Internet] [Doctoral dissertation]. Virginia Tech; 2002. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/27429.
Council of Science Editors:
Sernek M. Comparative Analysis of Inactivated Wood Surfaces. [Doctoral Dissertation]. Virginia Tech; 2002. Available from: http://hdl.handle.net/10919/27429
Virginia Tech
18.
Kaster, Jeffrey Allen.
Optimization of large beaded cellulose as a chromatographic support.
Degree: PhD, Chemical Engineering, 1993, Virginia Tech
URL: http://hdl.handle.net/10919/38397
► The design of existing beaded adsorbent materials for column-mode protein purification has emphasized the impact of diffusional transport phenomena upon adsorbent capacity. A design model…
(more)
▼ The design of existing beaded adsorbent materials for column-mode protein purification has emphasized the impact of diffusional transport phenomena upon adsorbent capacity. A design model is presented that optimizes molecular accessibility of proteins relative to the mechanical stability of the material by manipulation of size and solids content for uncross-linked cellulose beads. Cellulose beads of various sizes ranging from about 250 to 1000 pm diameter and having different solids contents were evaluated. Cellulose beads (1.2 mm diameter) gave pressure drops of less than 1 psi per cm of bed at superficial fluid velocities of 100 cm/min in a 1 5 cm bed. Solids content of greater than about 9% cellulose greatly reduced the permeability of large proteins such as thyroglobulin and p-Amylase into the beaded matrix at bead contacting times of 5 and 50 seconds. The amount of permeation in 3% cellulose beads by thyroglobulin at bead contacting times of 5 seconds was about tenfold larger than predicted by diffusion models using the diffusivity of the protein in water. The utility of a low solids content, large bead cellulose support was shown with immobilized IgG (Mr 155 kDa) capturing recombinant human Protein C (M, 62 kDa).
The amount of immobilized antibody was varied and immunosorptive capacity of 1 mm cellulose beads was found to be equivalent to that of 0.1 mm cross~linked agarose beads. The immobilization of antibodies to these supports was studied by photomicroscopy of cross-sectioned beads containing immobilized fluorescent labeled antibodies. While 75% of the antibody was immobilized within 0.07 mm of the cellulose bead surface at an antibody density of 1 mg antibody per ml of beads, an appreciable amounts of antibody immobilized deeper into the bead may have been utilized in order to yield capacities equivalent to the smaller agarose beads. The beaded cellulose supports derivatized to form either immunoaffinity or anion exchange matrices exhibited very low non-specific binding. Thus, the particle size, solids content, and extent of derivatization of cellulose matrices can be engineered so as to create matrices that provide high flow rates with low pressure drops while also having desirable adsorptive capacity for proteins.
Advisors/Committee Members: Velander, William H. (committeechair), Davis, Richey M. (committee member), Conger, William L. (committee member), Glasser, Wolfgang G. (committee member), Drohan, William N. (committee member).
Subjects/Keywords: Cellulose; LD5655.V856 1993.K378
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Kaster, J. A. (1993). Optimization of large beaded cellulose as a chromatographic support. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/38397
Chicago Manual of Style (16th Edition):
Kaster, Jeffrey Allen. “Optimization of large beaded cellulose as a chromatographic support.” 1993. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/38397.
MLA Handbook (7th Edition):
Kaster, Jeffrey Allen. “Optimization of large beaded cellulose as a chromatographic support.” 1993. Web. 11 Apr 2021.
Vancouver:
Kaster JA. Optimization of large beaded cellulose as a chromatographic support. [Internet] [Doctoral dissertation]. Virginia Tech; 1993. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/38397.
Council of Science Editors:
Kaster JA. Optimization of large beaded cellulose as a chromatographic support. [Doctoral Dissertation]. Virginia Tech; 1993. Available from: http://hdl.handle.net/10919/38397
Virginia Tech
19.
Eberhardt, Thomas Leonard.
Characterization of lignin deposition in <i>Pinus taeda</i> L. cell suspension cultures.
Degree: PhD, Wood Science and Forest Products, 1992, Virginia Tech
URL: http://hdl.handle.net/10919/38851
► <i>Pinus taeda</i> L. suspension culture cells were used to develop a model system to study the process of lignification occurring during the early stages of…
(more)
▼ <i>Pinus taeda</i> L. suspension culture cells were used to develop a model system to study the process of lignification occurring during the early stages of cell wall formation and maturation. Chemical, biochemical and histochemical analyses of the <i>P. taeda</i> suspension cultures grown with 2,4-dichlorophenoxyacetic acid (2,4-D) as the growth regulator did not provide conclusive evidence for lignin deposition. On the other hand, cultures in which 2,4-D was substituted with α-naphthaleneacetic acid (NAA) were shown to lignify. During this induction of lignification, limited cell wall thickening occurred since transmission electron microscopy of the 2,4-D grown cells showed only primary walls while the average cell wall thickness of the NAA-grown cells was consistent with secondary (S₁) layer formation. Despite the possibility of only limited lignin deposition in the 2,4-0 grown cells, secondary metabolism had occurred as evidenced by reversed-phase and chiral chromatographic separations which revealed the ability of these cells to produce enantiomerically pure (-)-matairesinol. Administrations of [1-¹³C], [2-¹³C ] and [3-¹³C ] specifically labeled phenylalanines to the <i>P. taeda</i> suspension cultures in medium containing NAA allowed the determination of lignin bonding patterns <i>in situ</i> by solid-state ¹³C NMR spectroscopy of the resulting ¹³C enriched cells.
Aqueous and organic solvent extractions and protease treatment yielded ¹³C enriched cell walls for solid-state ¹³C NMR spectroscopic analyses of the cell wall bound lignin component. Subsequently, an isolated lignin derivative from these cell walls was analyzed by solution-state ¹³C NMR spectroscopy and verified the assignments made in the solid-state. Accordingly, the above experiments represent the first demonstration of lignin bonding patterns <i>in situ</i> in a <i>Pinus</i> species as well as a suspension culture. This culture system possesses great potential as a model to thoroughly study the early stages of lignification.
Advisors/Committee Members: Lewis, Norman G. (committeechair), Ifju, Geza (committee member), Cramer, Carole L. (committee member), Glasser, Wolfgang G. (committee member), Hess, John L. (committee member), White, Robert H. (committee member).
Subjects/Keywords: Plant cell walls; LD5655.V856 1992.E237
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Eberhardt, T. L. (1992). Characterization of lignin deposition in <i>Pinus taeda</i> L. cell suspension cultures. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/38851
Chicago Manual of Style (16th Edition):
Eberhardt, Thomas Leonard. “Characterization of lignin deposition in <i>Pinus taeda</i> L. cell suspension cultures.” 1992. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/38851.
MLA Handbook (7th Edition):
Eberhardt, Thomas Leonard. “Characterization of lignin deposition in <i>Pinus taeda</i> L. cell suspension cultures.” 1992. Web. 11 Apr 2021.
Vancouver:
Eberhardt TL. Characterization of lignin deposition in <i>Pinus taeda</i> L. cell suspension cultures. [Internet] [Doctoral dissertation]. Virginia Tech; 1992. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/38851.
Council of Science Editors:
Eberhardt TL. Characterization of lignin deposition in <i>Pinus taeda</i> L. cell suspension cultures. [Doctoral Dissertation]. Virginia Tech; 1992. Available from: http://hdl.handle.net/10919/38851
Virginia Tech
20.
Zheng, Jun.
Studies of PF Resole / Isocyanate Hybrid Adhesives.
Degree: PhD, Wood Science and Forest Products, 2002, Virginia Tech
URL: http://hdl.handle.net/10919/25960
► Phenol-formaldehyde (PF) resole and polymeric diphenylmethane diisocyanate (PMDI) are two commonly used exterior thermosetting adhesives in the wood-based composites industry. There is an interest in…
(more)
▼ Phenol-formaldehyde (PF) resole and polymeric diphenylmethane diisocyanate (PMDI) are two commonly used exterior thermosetting adhesives in the wood-based composites industry. There is an interest in combining these two adhesives in order to benefit from their positive attributes while also neutralizing some of the negative ones. Although this novel adhesive system has been reportedly utilized in some limited cases, a fundamental understanding is lacking. This research serves this purpose by investigating some of the important aspects of this novel adhesive system.
The adhesive rheological and viscometric properties were investigated with an advanced rheometer. The resole/PMDI blends exhibited non-Newtonian flow behavior. The blend viscosity and stability were dependent on the blend ratio, mixing rate and time. The adhesive penetration into wood was found to be dependent on the blend ratio and correlated with the blend viscosity. By using dynamic mechanical analysis, the blend cure speed was found to increase with the PMDI content. Mode I fracture testing of resole/PMDI hybrid adhesive bonded wood specimens indicated the dependence of bondline fracture energy on the blend ratio. The 75/25 PF/PMDI blend exhibited a high fracture energy with a fast cure speed and processable viscosity. Exposure to water-boil weathering severely deteriorated the fracture energies of the hybrid adhesive bondlines.
More detailed chemistry and morphological studies were performed with cross-polarization nuclear magnetic resonance and 13C, 15N-doubly labeled PMDI. A spectral decomposition method was used to obtain information regarding chemical species concentration and relaxation behavior of the contributing components within the major nitrogen resonance. Different urethane concentrations were present in the cured blend bondlines. Water-boil weathering and thermal treatment at elevated temperatures (e.
g. > 200°C) caused reduced urethane concentrations in the bondline. Solid-state relaxation parameters revealed a heterogeneous structure in the non-weathered blends. Water boil weathering caused a more uniform relaxation behavior in the blend bondline.
By conducting this research, more fundamental information regarding the PF/PMDI hybrid adhesives will become available. This information will aid in the evaluation of, and improve the potential use of PF/PMDI hybrid adhesives for wood-based composites.
Advisors/Committee Members: Frazier, Charles E. (committeechair), Wilkes, Garth L. (committee member), Glasser, Wolfgang G. (committee member), Helm, Richard Frederick (committee member), Kamke, Frederick A. (committee member).
Subjects/Keywords: fracture testing; adhesives; PF resole; wood adhesion; spectral decomposition; solid-state NMR; isocyanate; urethane; weathering
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Zheng, J. (2002). Studies of PF Resole / Isocyanate Hybrid Adhesives. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/25960
Chicago Manual of Style (16th Edition):
Zheng, Jun. “Studies of PF Resole / Isocyanate Hybrid Adhesives.” 2002. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/25960.
MLA Handbook (7th Edition):
Zheng, Jun. “Studies of PF Resole / Isocyanate Hybrid Adhesives.” 2002. Web. 11 Apr 2021.
Vancouver:
Zheng J. Studies of PF Resole / Isocyanate Hybrid Adhesives. [Internet] [Doctoral dissertation]. Virginia Tech; 2002. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/25960.
Council of Science Editors:
Zheng J. Studies of PF Resole / Isocyanate Hybrid Adhesives. [Doctoral Dissertation]. Virginia Tech; 2002. Available from: http://hdl.handle.net/10919/25960
Virginia Tech
21.
Schmidt, Robert G.
Aspects of Wood Adhesion: Applications of 13C CP/MAS NMR and Fracture Testing.
Degree: PhD, Wood Science and Forest Products, 1998, Virginia Tech
URL: http://hdl.handle.net/10919/30352
► Phenol Formaldehyde (PF) and polymeric isocyanate (pMDI) are the two main types of adhesives used in the production of structural wood-based composites. Much is unknown…
(more)
▼ Phenol Formaldehyde (PF) and polymeric isocyanate (pMDI) are the two main types of adhesives used in the production of structural wood-based composites. Much is unknown about various aspects of adhesion between these two types of resins and wood. The present research describes the development of techniques which will permit an enhanced understanding of 1.) the extent of cure of PF within a wood based composite, 2.) the scale of molecular level interactions between PF and pMDI and wood, 3.) mechanical performance and durability of wood-adhesive bonds.
Correlations were established between conventional methods of characterization of neat PF (thermomechanical analysis, swelling studies) and measurements made using 13C CP/MAS NMR. These correlations were then utilized to characterize PF cured in the presence of wood. The use of 13C labeled PF allowed estimates of relative degrees of resin conversion to be made. The use of 13C and deuterium labeled PF allowed qualitative estimates of resin molecular rigidity to be made. The scale of molecular level interactions between PF and pMDI and wood was probed using NMR relaxation experiments. Evidence was shown to suggest the formation of an interpenetrating polymer network (IPN) morphology existing at both types of wood-resin interphases. The formation of the IPN morphology was strongly influenced by resin molecular weight, cure temperature and the presence of solvent.
A new test geometry for the evaluation of the fracture toughness of wood-adhesive bonds was developed. Consistent and reliable results were obtained. It was found that low molecular weight PF possessed enhanced durability over high molecular weight.
Advisors/Committee Members: Frazier, Charles E. (committeechair), Wightman, James P. (committee member), Kamke, Frederick A. (committee member), Ward, Thomas C. (committee member), Glasser, Wolfgang G. (committee member).
Subjects/Keywords: interpenetrating network formation; IPN; pMDI; isocyanate; phenol formaldehyde; PF; mechanisms of adhesion
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Schmidt, R. G. (1998). Aspects of Wood Adhesion: Applications of 13C CP/MAS NMR and Fracture Testing. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/30352
Chicago Manual of Style (16th Edition):
Schmidt, Robert G. “Aspects of Wood Adhesion: Applications of 13C CP/MAS NMR and Fracture Testing.” 1998. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/30352.
MLA Handbook (7th Edition):
Schmidt, Robert G. “Aspects of Wood Adhesion: Applications of 13C CP/MAS NMR and Fracture Testing.” 1998. Web. 11 Apr 2021.
Vancouver:
Schmidt RG. Aspects of Wood Adhesion: Applications of 13C CP/MAS NMR and Fracture Testing. [Internet] [Doctoral dissertation]. Virginia Tech; 1998. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/30352.
Council of Science Editors:
Schmidt RG. Aspects of Wood Adhesion: Applications of 13C CP/MAS NMR and Fracture Testing. [Doctoral Dissertation]. Virginia Tech; 1998. Available from: http://hdl.handle.net/10919/30352
Virginia Tech
22.
Frazier, Charles Edward.
Synthesis and characterization of fluorinated cellulose derivatives.
Degree: PhD, Wood Science and Forest Products, 1992, Virginia Tech
URL: http://hdl.handle.net/10919/39980
► The synthesis of fluorinated cellulose derivatives was pursued for the purpose of investigating the effects of fluorine on the interfacial properties of cellulose derivatives, in…
(more)
▼ The synthesis of fluorinated cellulose derivatives was pursued for the purpose of investigating the effects of fluorine on the interfacial properties of cellulose derivatives, in multiphase materials. Synthetic approaches included: 1) the replacement of hydroxyl groups on cellulose with fluorine using fluoride displacement chemistry, or direct, one step fluorination 2) the replacement of hydroxyl groups on hydroxypropyl cellulose, HPC, with direct one step fluorinating agents, or 3) the conventional derivatization of cellulose with prefluorinated agents. Fluoride displacement of cellulose sulfonate esters was plagued low yields, and was therefore ineffective. Direct cellulose fluorination with aminofluorosulfur, and aminofluorocarbon reagents was effective for the surface fluorination of cellulose. However, the bulk, homogeneous fluorination of cellulose was complicated by side reactions that often precluded fluorination. Cellulose dissolved in DMAC/LiCI underwent simultaneous chlorination, and branching reactions when treated with dialkylaminosulfur trifluoride, DAST. Branching resulted from an anhydrous HF catalyzed trans-glycosidation reaction, which produced mainly (3-1,6 branching. Serendipitously, this discovery allows for the first known synthesis of long chain branched cellulose derivatives, with increased molar mass, and increased polydispersity. Treatment of HPC with DAST and FAR gave good levels of fluorination; however, the HF catalyzed gelation was always a complicating factor. The lower reactivity of FAR allowed for partial control of gelation with the use of nonnucleophilic bases.
The easiest way to introduce fluorine was to perform conventional derivatization using prefluorinated reagents such as for the synthesis of fluorobenzyl cellulose. Mixed benzyl ethers of controlled fluorine content were made by altering the ratio of pfluorobenzyl chloride to benzyl chloride during reaction. 2-Dimensional NMR techniques were used to identify most proton and carbon resonances of cellulose and amylose fluorobenzyl ethers. Thermal analysis, solution analysis, and l3C spin-lattice relaxation experiments were used to compare the rod-like and coil-like behavior of the fluorobenzyl cellulose and amylose.
Polycaprolactone, PCL, was blended with tri-O-benzylated cellulose with different degrees of fluorination. PCL was found to be immiscible with all derivatives, of fluorine contents from 0 % to as high as 11.7%. PCL did display some degree of mechanical compatibility with all derivatives. The greatest compatibility was found with benzylated cellulose having fluorine contents slightly below the maximum. It was found that no specific interactions were occurring between peL and fluorobenzyl cellulose. The enhanced compatibility of the mixed fluorobenzyl/benzyl cellulose ethers was postulated to arise from intramolecular interactions, which served to enhance the mixing of the copolymeric mixed benzyl ethers with PCL.
Advisors/Committee Members: Glasser, Wolfgang G. (committeechair), Ward, Thomas C. (committee member), McGrath, James E. (committee member), Gibson, Harry W. (committee member), Taylor, Larry T. (committee member).
Subjects/Keywords: Fluorocarbohydrates Synthesis; Cellulose Synthesis; LD5655.V856 1992.F739
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Frazier, C. E. (1992). Synthesis and characterization of fluorinated cellulose derivatives. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/39980
Chicago Manual of Style (16th Edition):
Frazier, Charles Edward. “Synthesis and characterization of fluorinated cellulose derivatives.” 1992. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/39980.
MLA Handbook (7th Edition):
Frazier, Charles Edward. “Synthesis and characterization of fluorinated cellulose derivatives.” 1992. Web. 11 Apr 2021.
Vancouver:
Frazier CE. Synthesis and characterization of fluorinated cellulose derivatives. [Internet] [Doctoral dissertation]. Virginia Tech; 1992. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/39980.
Council of Science Editors:
Frazier CE. Synthesis and characterization of fluorinated cellulose derivatives. [Doctoral Dissertation]. Virginia Tech; 1992. Available from: http://hdl.handle.net/10919/39980
Virginia Tech
23.
Lei, Zhentian.
Monomeric Ellagitannins in Oaks and Sweetgum.
Degree: PhD, Wood Science and Forest Products, 2002, Virginia Tech
URL: http://hdl.handle.net/10919/27588
► Ellagitannins are plant phenolics characterized by biaryl-coupled gallic acid moieties esterified to a D-glucose core. They are widely distributed through higher plants. In the case…
(more)
▼ Ellagitannins are plant phenolics characterized by biaryl-coupled gallic acid moieties esterified to a D-glucose core. They are widely distributed through higher plants. In the case of oaks, ellagitannin concentrations in heartwood can reach up to 10% (dry wt. basis). These secondary metabolites are not only important physiologically but also influence the economic value and quality of wood products that contain them.
Efforts were made to develop and validate the methods used to quantify both soluble and insoluble ellagitannins. First, the efficiencies of the two commonly used extraction solvents, aqueous acetone and aqueous methanol were evaluated. The results showed that aqueous acetone is superior to aqueous methanol in obtaining higher vescalagin and castalagin yields. In a separate study, the method used for determining insoluble ellagitannins was found to under-estimate the contents of insoluble ellagitannins in wood products. Anhydrous methanolic HCl was found to be an excellent reagent for releasing insoluble ellagic acid and gallic acid (as methyl gallate) from biomass substrates. Optimization of both the reaction conditions and the gradient HPLC analysis has led to the development of a robust and reliable protocol.
The chemical stability of the two predominant ellagitannins in oaks (vescalagin and castalagin) were evaluated in aqueous methanol and water. It was found that oxygen, pH and higher temperature (60 °C) affect their stability with higher temperature being the most prominent factor. Both vescalagin and castalagin were found unstable in methanolic solutions. Vestalagin, however, is less stable than castalagin.
In the course of finding alternative models for ellagitannin biosynthesis study, both callus tissues and suspension cell cultures of white oak (Quercus alba) and sweetgum (Liquidambar styraciflua) were investigated for their possible use as models for ellagitannin biosynthesis. It was found that oak callus tissue cultures (Quercus alba) are capable of producing ellagitannins, and the production and profile of ellagitannins can be modified by adjusting the media composition. Comparison of extracts from the heartwood of Quercus alba with those from callus tissue reveals that they have similar ellagitannin profiles. Through manipulation of the media nitrogen and copper concentrations the callus tissue produced almost 3 times as much castalagin and vescalagin. Suspension cells of Quercus alba and Liquidambar styraciflua were found to be unsuitable for the study of biosynthesis of ellagitannins. These cells either did not produce any detectable level of ellagitannins or the production was unstable. Although the suspension cells could be elicited to produce ellagic acid with glycanases (Driselase), the levels of ellagic acid were too low for quantitative metabolic studies.
A method using high performance liquid chromatography â mass spectrometry was developed and optimized with purified ellagitannins. Ellagitannins analyzed under the optimal conditions all provide base peaks of (M-H)- from…
Advisors/Committee Members: Helm, Richard Frederick (committeechair), Glasser, Wolfgang G. (committee member), Frazier, Charles E. (committee member), Kingston, David G. I. (committee member), Hess, John L. (committee member).
Subjects/Keywords: Oak; HPLC/ESI-MS; Sweetgum; Ellagitannins
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Lei, Z. (2002). Monomeric Ellagitannins in Oaks and Sweetgum. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/27588
Chicago Manual of Style (16th Edition):
Lei, Zhentian. “Monomeric Ellagitannins in Oaks and Sweetgum.” 2002. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/27588.
MLA Handbook (7th Edition):
Lei, Zhentian. “Monomeric Ellagitannins in Oaks and Sweetgum.” 2002. Web. 11 Apr 2021.
Vancouver:
Lei Z. Monomeric Ellagitannins in Oaks and Sweetgum. [Internet] [Doctoral dissertation]. Virginia Tech; 2002. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/27588.
Council of Science Editors:
Lei Z. Monomeric Ellagitannins in Oaks and Sweetgum. [Doctoral Dissertation]. Virginia Tech; 2002. Available from: http://hdl.handle.net/10919/27588
Virginia Tech
24.
Das, Sudipto.
Wood/Polymeric Isocyanate Resin Interactions: Species dependence.
Degree: PhD, Macromolecular Science and Engineering, 2005, Virginia Tech
URL: http://hdl.handle.net/10919/28745
► The performance of polymeric diphenylmethane diisocyanate (PMDI) resin is known to be highly dependent on the wood species. This species dependence may be due to…
(more)
▼ The performance of polymeric diphenylmethane diisocyanate (PMDI) resin is known to be highly dependent on the wood species. This species dependence may be due to differences in: cure chemistry, interphase morphology, or both of these factors. This study addresses aspects of the cure chemistry and interphase morphology of wood/PMDI bondlines; specifically these effects are compared using two woods: yellow-poplar and southern pine.
In this study, the cure chemistry of wood-PMDI system was analyzed with solid state NMR (SSNMR) using wood samples cured with doubly labeled (15N,13C) PMDI resin. The kinetics of PMDI cure in the presence of wood was analyzed with differential scanning calorimetry. Thermogravimetric analysis was used to analyze the effect of resin impregnation on the degradation patterns of wood. The wood-PMDI bond morphology was probed with dynamic and static (creep) mechanical analyses in both dry and plasticized conditions. The effect of resin on wood polymer relaxations was quantitatively analyzed by both the time-temperature superposition principle and the Kohlrausch-Williams-Watts equation.
The presence of a small but statistically significant species effect was observed on both the cure chemistry and bond morphology of wood-PMDI system at low cure temperatures. The cure of PMDI resin was found to be significantly faster in pine relative to corresponding poplar samples. Resin impregnation showed a significant species dependent effect on the wood mechanical properties; the resinated pine samples showed increase in compliance while the corresponding poplar samples became stiffer.
The in situ lignin relaxation was studied with both dynamic and static modes, using plasticized wood samples. Results showed that the lignin relaxation was slightly affected by resin impregnation in both woods, but the effect was relatively larger in pine. Static experiments of dry wood samples showed a significant reduction in the interchain interactions of wood polymers in pine samples, exclusively. Investigation of plasticized pine samples, which focuses on the in situ lignin relaxations, showed only minor changes with resin impregnation. This led us to hypothesize that the large changes observed in dry samples, were due to the in situ amorphous polysaccharides. The wood-PMDI interactions were significantly reduced upon acetylation of wood. This study also discusses three new and highly sensitive methods for the analysis of wood-resin interactions.
Advisors/Committee Members: Frazier, Charles E. (committeechair), Glasser, Wolfgang G. (committee member), Roman, Maren (committee member), Zink-Sharp, Audrey G. (committee member), Wilkes, Garth L. (committee member).
Subjects/Keywords: wood species; solid-state nuclear magnetic resosnance; differential scanning calorimetry; dynamic mechanical analysis; thermogravimetric analysis; creep; polymeric isocyanate resin
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Das, S. (2005). Wood/Polymeric Isocyanate Resin Interactions: Species dependence. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/28745
Chicago Manual of Style (16th Edition):
Das, Sudipto. “Wood/Polymeric Isocyanate Resin Interactions: Species dependence.” 2005. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/28745.
MLA Handbook (7th Edition):
Das, Sudipto. “Wood/Polymeric Isocyanate Resin Interactions: Species dependence.” 2005. Web. 11 Apr 2021.
Vancouver:
Das S. Wood/Polymeric Isocyanate Resin Interactions: Species dependence. [Internet] [Doctoral dissertation]. Virginia Tech; 2005. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/28745.
Council of Science Editors:
Das S. Wood/Polymeric Isocyanate Resin Interactions: Species dependence. [Doctoral Dissertation]. Virginia Tech; 2005. Available from: http://hdl.handle.net/10919/28745
Virginia Tech
25.
Ballerini, Aldo A.
Cure of aqueous phenol-formaldehyde resin at elevated water vapor pressures.
Degree: PhD, Wood Science and Forest Products, 1994, Virginia Tech
URL: http://hdl.handle.net/10919/40045
► The intent of this research was to enhance our knowledge of aqueous phenolformaldehyde resin cure as it is affected by the elevated water vapor pressures…
(more)
▼ The intent of this research was to enhance our knowledge of aqueous phenolformaldehyde
resin cure as it is affected by the elevated water vapor pressures that occur during hot-pressing of a wood-based composite. Microdielectric spectroscopy (DEA) was used to monitor the cure reaction, and thermomechanical analysis (TMA), swelling tests and scanning electron microscopy (SEM) techniques were used to characterize the final
resin-network. Microdielectric results showed that as the water vapor pressure of the
sy stem increases the time to gelation increases. It was also found that the injection of
saturated water vapor sharply decreased the gelation time when compared to the other
water vapor environmental conditions. In addition, it was found that the higher the water
vapor pressure the lower the residual ion viscosity. Thermomechanical analysis and
swelling test experiments showed that as the water vapor pressure increases the glass
transition temperature and the cross-link density of the cured resin-network decreases.
Considerable differences in the morphology of the network were found using SEM. Thus,
it can be established that during the curing process under elevated water vapor pressures
of a liquid phenol-formaldehyde adhesi ve some water is trapped into the resin network
and it is acting as a plasticizer.
A theoretical approach to model the cure kinetics of phenol-formaldehyde has been
developed. The model is based on the occurrence of two simultaneous processes
(condensation polymerization and evaporation of water) and on the concentration
dependency of the activation energy of polymerization.
Advisors/Committee Members: Kamke, Frederick A. (committeechair), Frazier, Andrew E. (committee member), Glasser, Wolfgang G. (committee member), Youngs, Robert L. (committee member), Wightman, James P. (committee member).
Subjects/Keywords: Phenolic resins Curing.; LD5655.V856 1994.B356
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Ballerini, A. A. (1994). Cure of aqueous phenol-formaldehyde resin at elevated water vapor pressures. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/40045
Chicago Manual of Style (16th Edition):
Ballerini, Aldo A. “Cure of aqueous phenol-formaldehyde resin at elevated water vapor pressures.” 1994. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/40045.
MLA Handbook (7th Edition):
Ballerini, Aldo A. “Cure of aqueous phenol-formaldehyde resin at elevated water vapor pressures.” 1994. Web. 11 Apr 2021.
Vancouver:
Ballerini AA. Cure of aqueous phenol-formaldehyde resin at elevated water vapor pressures. [Internet] [Doctoral dissertation]. Virginia Tech; 1994. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/40045.
Council of Science Editors:
Ballerini AA. Cure of aqueous phenol-formaldehyde resin at elevated water vapor pressures. [Doctoral Dissertation]. Virginia Tech; 1994. Available from: http://hdl.handle.net/10919/40045
Virginia Tech
26.
Hofmann, Klaus.
Synthesis, properties, and morphology of lignin based epoxy resins.
Degree: PhD, Materials Engineering Science, 1991, Virginia Tech
URL: http://hdl.handle.net/10919/37407
► Star-like lignin-poly(propylene oxide) copolymers were prepared by chain-extending steam exploded lignins (tulipifera liriodendron) with propylene oxide and by subsequent endcapping with ethylene oxide. Epoxidation of…
(more)
▼ Star-like lignin-poly(propylene oxide) copolymers were prepared by chain-extending steam exploded lignins (tulipifera liriodendron) with propylene oxide and by subsequent endcapping with ethylene oxide. Epoxidation of these copolymers was carried out with epichlorohydrin at room temperature, using KOH as oxyanion forming reagent. The epoxidized compounds were fractionated by solvent precipitation to remove poly(alkylene oxide) homopolymers and to prepare fractions of narrow molecular weight distributions.
The epoxides were cross-linked with meta phenylene diamine yielding thermosets which were, depending on lignin content, either low modulus elastomers, or high modulus materials with considerable ductility. The modulus of elasticity was a strong and linear function of lignin content, whereby the highest value was 1100MPa (57%f lignin).
The curing reaction was of nth-order type, whereby the reaction order changed from close to one at the beginning of the curing reaction to 2, once the reaction becomes diffusion controlled. Curing induced partial demixing of the lignin and poly(propylene oxide) phases which yielded a secondary structure where lignin rich domains in the order of IOnm were interspersed in a matrix of lignin poor material. However, from TEM and 13C solid state cross-polarized NMR analyses it was evident that the domain structure was not that of a classical micro-phase separated copolymer with well defined phase boundaries, but rather had broad interphases. Additionally, the results of multifrequency dynamic mechanical thermal analysis showed that the lignin containing thermosets have very broad glass transition ranges which most likely were due to transitional phase inhomogeneities and provided these materials with good vibrational damping ability.
Advisors/Committee Members: Glasser, Wolfgang G. (committeechair), Kamke, Frederick A. (committee member), Loos, Alfred C. (committee member), Ward, Thomas C. (committee member), Wilkes, Garth L. (committee member).
Subjects/Keywords: Epoxy resins Research; LD5655.V856 1991.H646
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Hofmann, K. (1991). Synthesis, properties, and morphology of lignin based epoxy resins. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/37407
Chicago Manual of Style (16th Edition):
Hofmann, Klaus. “Synthesis, properties, and morphology of lignin based epoxy resins.” 1991. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/37407.
MLA Handbook (7th Edition):
Hofmann, Klaus. “Synthesis, properties, and morphology of lignin based epoxy resins.” 1991. Web. 11 Apr 2021.
Vancouver:
Hofmann K. Synthesis, properties, and morphology of lignin based epoxy resins. [Internet] [Doctoral dissertation]. Virginia Tech; 1991. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/37407.
Council of Science Editors:
Hofmann K. Synthesis, properties, and morphology of lignin based epoxy resins. [Doctoral Dissertation]. Virginia Tech; 1991. Available from: http://hdl.handle.net/10919/37407
Virginia Tech
27.
Davé, Vipul.
Cellulose-based fibers from liquid crystalline solutions.
Degree: PhD, Materials Engineering Science, 1992, Virginia Tech
URL: http://hdl.handle.net/10919/39205
Subjects/Keywords: Cellulose fibers; LD5655.V856 1992.D383
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Davé, V. (1992). Cellulose-based fibers from liquid crystalline solutions. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/39205
Chicago Manual of Style (16th Edition):
Davé, Vipul. “Cellulose-based fibers from liquid crystalline solutions.” 1992. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/39205.
MLA Handbook (7th Edition):
Davé, Vipul. “Cellulose-based fibers from liquid crystalline solutions.” 1992. Web. 11 Apr 2021.
Vancouver:
Davé V. Cellulose-based fibers from liquid crystalline solutions. [Internet] [Doctoral dissertation]. Virginia Tech; 1992. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/39205.
Council of Science Editors:
Davé V. Cellulose-based fibers from liquid crystalline solutions. [Doctoral Dissertation]. Virginia Tech; 1992. Available from: http://hdl.handle.net/10919/39205
Virginia Tech
28.
Wolcott, Michael P.
Modeling viscoelastic cellular materials for the pressing of wood composites.
Degree: PhD, Materials Engineering Science, 1989, Virginia Tech
URL: http://hdl.handle.net/10919/54813
► With the large number and diversity of materials available today, the ability of the manufacturer to control properties is critical for the success of a…
(more)
▼ With the large number and diversity of materials available today, the ability of the manufacturer to control properties is critical for the success of a product in the market. Although we have little or no control over the engineering properties of solid wood, the potential for the design of material properties in composites is great. Large strides are presently being made in the design of non-veneer structural panels by using material science principles. However, a large gap in our knowledge of the composite system is in the understanding of how raw material properties and processing variables interact to influence the internal geometry and material properties of the components in situ. The ability to use production variables to control material properties of the composite is an extremely valuable tool.
The goal of this research is to provide an understanding of how the heat and mass transfer inside a flakeboard during pressing, interacts with the viscoelastic behavior of individual flakes to influence density gradient formation and in situ flake properties. The specific objectives:
l. To use observed changes in the temperature and gas pressure of the internal environment of panels during the pressing cycle to describe the composition of the gas phase.
2. To use the calculated composition of the gas phase and measured temperature for the internal environment as boundary conditions for a fundamental heat and mass transfer model to
access changes in the temperature and moisture content of the wood component during pressing.
3. To use the temperature and moisture content relations above to qualitatively relate press conditions to the formation of density gradients through changes in the glass transition temperature of the amorphous polymers in wood.
4. To utilize micromechanical models of cellular materials in conjunction with linear viscoelasticity of polymers to develop a nonlinear viscoelasticity model for wood in transverse compression.
The approach couples the viscoelastic behavior of the amorphous polymers in wood with the structure imposed by anatomy. These theories, if applicable to wood, can greatly simplify the study of many similar systems combining environmental conditions and mechanical properties.
Advisors/Committee Members: Kamke, Frederick A. (committeechair), Dillard, David A. (committee member), Glasser, Wolfgang G. (committee member), Youngs, Robert L. (committee member), McLain, Thomas E. (committee member), Reifsnider, Kenneth L. (committee member).
Subjects/Keywords: LD5655.V856 1989.W676; Composite materials – Research; Wood – Research
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Wolcott, M. P. (1989). Modeling viscoelastic cellular materials for the pressing of wood composites. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/54813
Chicago Manual of Style (16th Edition):
Wolcott, Michael P. “Modeling viscoelastic cellular materials for the pressing of wood composites.” 1989. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/54813.
MLA Handbook (7th Edition):
Wolcott, Michael P. “Modeling viscoelastic cellular materials for the pressing of wood composites.” 1989. Web. 11 Apr 2021.
Vancouver:
Wolcott MP. Modeling viscoelastic cellular materials for the pressing of wood composites. [Internet] [Doctoral dissertation]. Virginia Tech; 1989. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/54813.
Council of Science Editors:
Wolcott MP. Modeling viscoelastic cellular materials for the pressing of wood composites. [Doctoral Dissertation]. Virginia Tech; 1989. Available from: http://hdl.handle.net/10919/54813
Virginia Tech
29.
Renneckar, Scott Harold.
Modification of Wood Fiber with Thermoplastics by Reactive Steam-Explosion.
Degree: PhD, Wood Science and Forest Products, 2004, Virginia Tech
URL: http://hdl.handle.net/10919/11239
► For the first time, a novel processing method of co-refining wood and polyolefin (PO) by steam-explosion was scientifically explored for wood-thermoplastic composites without a coupling…
(more)
▼ For the first time, a novel processing method of co-refining wood and polyolefin (PO) by steam-explosion was scientifically explored for wood-thermoplastic composites without a coupling agent. Traditional studies have addressed the improvement of adhesion between components of wood thermoplastic composites through the use of coupling agents such as maleated PO. The objective of this study was to increase adhesion between wood and PO through reactive processing conditions of steam-explosion. PO characteristics, such as type (polyethylene or polypropylene), form (pellet, fiber, or powder) and melt viscosity were studied along with oxygen gas content of the steam-explosion reactor vessel. Modification of co-processed wood fiber was characterized in four studies: microscopy analysis of dispersion of PO with wood fiber, sorption properties of co-processed material, chemical analysis of fractionated components, and morphological investigation of co-processed material. Two additional studies are listed in the appendices that relate to adsorption of amphiphilic polymers to the cellulose fiber surface, which is one hypothesis of fiber surface modification by co-steam-explosion.
Microscopy studies revealed that PO melt viscosity was found to influence the degree of dispersion and uniformity of the steam-exploded material. The hygroscopic nature of the co-processed fiber declined as shown by sorption isotherm data. Furthermore, a water vapor kinetics study found that all co-refined material had increased initial diffusion coefficients compared to the control fiber. Chemical changes in fractionated components were PO-type dependent. Lignin extracted from co-processed wood and polyethylene showed PO enrichment determined from an increase of methylene stretching in the Fourier Transform infrared subtraction spectra, while lignin from co-processed wood and polypropylene did not. Additionally, extracted PO showed indirect signs of oxidation as reflected by fluorescence studies. Solid state nuclear magnetic resonance spectroscopy revealed a number of differences in the co-processed materials such as increased cellulose crystallinity, new covalent linkages and an alternative distribution of components on the nanoscale reflected in the T1Ï relaxation parameter.
Steam-explosion was shown to modify wood fiber through the addition of "non-reactive" polyolefins without the need for coupling agents. In light of these findings, co-refining by steam-explosion should be viewed as a new reactive processing method for wood thermoplastic composites.
Advisors/Committee Members: Ducker, William A. (committee member), Frazier, Charles E. (committee member), Gatenholm, Paul (committee member), Ifju, Geza (committee member), Rials, Timothy (committee member), Zink-Sharp, Audrey G. (committeecochair), Glasser, Wolfgang G. (committeecochair).
Subjects/Keywords: confocal laser scanning microscopy; 13C NMR; fractionation; thermogravimetric analysis; biopolymer; cellulose
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Renneckar, S. H. (2004). Modification of Wood Fiber with Thermoplastics by Reactive Steam-Explosion. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/11239
Chicago Manual of Style (16th Edition):
Renneckar, Scott Harold. “Modification of Wood Fiber with Thermoplastics by Reactive Steam-Explosion.” 2004. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/11239.
MLA Handbook (7th Edition):
Renneckar, Scott Harold. “Modification of Wood Fiber with Thermoplastics by Reactive Steam-Explosion.” 2004. Web. 11 Apr 2021.
Vancouver:
Renneckar SH. Modification of Wood Fiber with Thermoplastics by Reactive Steam-Explosion. [Internet] [Doctoral dissertation]. Virginia Tech; 2004. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/11239.
Council of Science Editors:
Renneckar SH. Modification of Wood Fiber with Thermoplastics by Reactive Steam-Explosion. [Doctoral Dissertation]. Virginia Tech; 2004. Available from: http://hdl.handle.net/10919/11239
Virginia Tech
30.
Johnson, Richard Kwesi.
TEMPO-oxidized Nanocelluloses: Surface Modification and use as Additives in Cellulosic Nanocomposites.
Degree: PhD, Macromolecular Science and Engineering, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/29342
► The process of TEMPO-mediated oxidation has gained broad usage towards the preparation of highly charged, carboxyl-functionalized polysaccharides. TEMPO-oxidized nanocelluloses (TONc) of high surface charge and…
(more)
▼ The process of TEMPO-mediated oxidation has gained broad usage towards the preparation of highly charged, carboxyl-functionalized polysaccharides. TEMPO-oxidized nanocelluloses (TONc) of high surface charge and measuring 3 to 5 nm in width have been recently prepared from TEMPO-oxidized pulp. This study examines as-produced and surface-hydrophobized TONc as reinforcing additives in cellulosic polymer matrices. In the first part of the work, covalent (amidation) and non-covalent (ionic complexation) coupling were compared as treatment techniques for the hydrophobization of TONc surfaces with octadecylamine (ODA). Subsequently, TONc and its covalently coupled derivative were evaluated as nanofiber reinforcements in a cellulose acetate butyrate (CAB) matrix. The properties of the resulting nanocomposites were compared with those of similarly prepared ones reinforced with conventional microfibrillated cellulose (MFC).
It was found that both ionic complexation and amidation resulted in complete conversion of carboxylate groups on TONc surfaces. As a result of surface modification, the net crystallinity of TONc was lowered by 15 to 25% but its thermal decomposition properties were not significantly altered. With respect to nanocomposite performance, the maximum TONc reinforcement of 5 vol % produced negligible changes to the optical transmittance behavior and a 22-fold increase in tensile storage modulus in the glass transition region of CAB. In contrast, hydrophobized TONc and MFC deteriorated the optical transmittance of CAB by ca 20% and increased its tensile storage modulus in the glass transition region by only 3.5 and 7 times respectively. These differences in nanocomposite properties were attributed to homogeneous dispersion of TONc compared to aggregation of both the hydrophobized derivative and the MFC reference in CAB matrix. A related study comparing TONc with MFC and cellulose nanocrystals (CNC) as reinforcements in hydroxypropylcellulose (HPC), showed TONc reinforcements as producing the most significant changes to HPC properties. The results of dynamic mechanical analysis and creep compliance measurements could be interpreted based on similar arguments as those made for the CAB-based nanocomposites.
Overall, this work revealed that the use of TONc (without the need for surface hydrophobization) as additives in cellulosic polymer matrices leads to superior reinforcing capacity and preservation of matrix transparency compared to the use of conventional nanocelluloses.
Advisors/Committee Members: Zink-Sharp, Audrey G. (committeechair), Roman, Maren (committee member), Frazier, Charles E. (committee member), Glasser, Wolfgang G. (committee member), Renneckar, Scott H. (committee member), Esker, Alan R. (committee member).
Subjects/Keywords: ionic complexation; amidation; octadecylamine; surface modification; nanocomposite; TEMPO-oxidized; nanocellulose; thermal decomposition
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Johnson, R. K. (2010). TEMPO-oxidized Nanocelluloses: Surface Modification and use as Additives in Cellulosic Nanocomposites. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/29342
Chicago Manual of Style (16th Edition):
Johnson, Richard Kwesi. “TEMPO-oxidized Nanocelluloses: Surface Modification and use as Additives in Cellulosic Nanocomposites.” 2010. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/29342.
MLA Handbook (7th Edition):
Johnson, Richard Kwesi. “TEMPO-oxidized Nanocelluloses: Surface Modification and use as Additives in Cellulosic Nanocomposites.” 2010. Web. 11 Apr 2021.
Vancouver:
Johnson RK. TEMPO-oxidized Nanocelluloses: Surface Modification and use as Additives in Cellulosic Nanocomposites. [Internet] [Doctoral dissertation]. Virginia Tech; 2010. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/29342.
Council of Science Editors:
Johnson RK. TEMPO-oxidized Nanocelluloses: Surface Modification and use as Additives in Cellulosic Nanocomposites. [Doctoral Dissertation]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/29342
. 
Open Access Theses and Dissertations