You searched for +publisher:"Virginia Tech" +contributor:("Kamke, Frederick A.").
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29 total matches.
Virginia Tech
1.
Scott, Keith Alan.
Economic Feasibility of Implementing a Resin Distribution Measurement System for MDF Fiber.
Degree: MS, Wood Science and Forest Products, 2001, Virginia Tech
URL: http://hdl.handle.net/10919/31835 
► There have been successful techniques developed to measure resin distribution of phenol-formaldehyde adhesive on several types of wood surfaces. However, a technique that quantitatively measures…
(more)
▼ There have been successful techniques developed to measure resin distribution of phenol-formaldehyde adhesive on several types of wood surfaces. However, a technique that quantitatively measures UF resin on wood surfaces has been a problem because UF resin is colorless on wood fiber. The first objective of this study was to develop a technique to quantitatively measure surface area coverage and statistical distribution of urea-formaldehyde (UF) resin on medium density fiberboard (MDF) fiber. Two techniques were evaluated to quantitatively measure UF resin. One technique treated the resinated fiber with a reactive stain, such that the resin and wood could be distinguished and separated using digital image analysis. An epi-fluorescence microscope, color video camera, A/D image capture board, and image analysis software were used to measure the percent of resin coverage on the wood surface. The measured resin coverage of the treated fibers did not correlate with the target resin loading level. The other technique added ultraviolet dye to the resin and measured the distribution of resin with an image analysis system. The results of a mill trial confirmed the accuracy of the technique. This system has potential to be incorporated into a mill setting, which will provide MDF mills with a method of determining how resin is being distributed on their fiber.
The second objective of this study was to identify factors that would influence the technique's acceptance among MDF mills. A questionnaire was developed, pretested, and sent to every MDF mill in the United States. The method of adding UV dye into the resin was favorable to most mills and could be tested either on-site or by a third-party company. This allows MDF mills to determine potential problems with their blending process. This method saves time and money since it is a proactive measure rather than a reactive measure. It should also lead to a more uniform and consistent product, which is the goal of every MDF mill.
Advisors/Committee Members: Frazier, Charles E. (committee member), Smith, Robert A. (committeecochair), Kamke, Frederick A. (committeecochair).
Subjects/Keywords: adhesive measurement; Wood Science; UF resin
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APA (6th Edition):
Scott, K. A. (2001). Economic Feasibility of Implementing a Resin Distribution Measurement System for MDF Fiber. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/31835
Chicago Manual of Style (16th Edition):
Scott, Keith Alan. “Economic Feasibility of Implementing a Resin Distribution Measurement System for MDF Fiber.” 2001. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/31835.
MLA Handbook (7th Edition):
Scott, Keith Alan. “Economic Feasibility of Implementing a Resin Distribution Measurement System for MDF Fiber.” 2001. Web. 11 Apr 2021.
Vancouver:
Scott KA. Economic Feasibility of Implementing a Resin Distribution Measurement System for MDF Fiber. [Internet] [Masters thesis]. Virginia Tech; 2001. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/31835.
Council of Science Editors:
Scott KA. Economic Feasibility of Implementing a Resin Distribution Measurement System for MDF Fiber. [Masters Thesis]. Virginia Tech; 2001. Available from: http://hdl.handle.net/10919/31835
Virginia Tech
2.
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
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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
3.
Scott, Brian Cameron.
Evaluation of Phenol Formaldehyde Resin Cure Rate.
Degree: MS, Wood Science and Forest Products, 2005, Virginia Tech
URL: http://hdl.handle.net/10919/33222
► Cure time is often the bottleneck of composite manufacturing processes, therefore it is important to understand the cure of todayâ s thermosetting adhesives. This research…
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▼ Cure time is often the bottleneck of composite manufacturing processes, therefore it is important to understand the cure of todayâ s thermosetting adhesives. This research attempts to characterize the cure rate of two commercial phenol-formaldehyde adhesives. Two methods are used, parallel-plate rheometry and dielectric spectroscopy. Viscosity data from a parallel-plate rheometer may be used to track the advance of polymerization as a function of temperature. This data can then be used to optimize press conditions and reduce production times and costs.
The research will further examine resin cure through dielectric analysis; such a technique could monitor resin cure directly and in real-time press situations. Hot-pressing processes could conceivably no longer require a set press schedule; instead they would be individually set based on dielectric data for every press batch. Such a system may lead to a more efficient and uniform product because press times could be based on individual press cycles instead of entire product lines. A more likely scenario, however, is the use of in situ adhesive cure monitoring for troubleshooting or press schedule development.
This research characterized the cure of two phenol-formaldehyde resins using parallel-plate rheometry, fringe-field dielectric analysis, and parallel-plate dielectric analysis. The general shape of the storage modulus vs. time curve and the gel and vitrification points in a temperature ramp were found.
Both dielectric analysis techniques were able to characterize trends in the resin cure and detect points such as vitrification. The two techniques were also found to be comparable when the cure profiles of similar conditions were examined.
Advisors/Committee Members: Kamke, Frederick A. (committeechair), Frazier, Charles E. (committee member), Loferski, Joseph R. (committee member).
Subjects/Keywords: parallel-plate rheometry; thermoset resin cure; dielectric analysis
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APA (6th Edition):
Scott, B. C. (2005). Evaluation of Phenol Formaldehyde Resin Cure Rate. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/33222
Chicago Manual of Style (16th Edition):
Scott, Brian Cameron. “Evaluation of Phenol Formaldehyde Resin Cure Rate.” 2005. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/33222.
MLA Handbook (7th Edition):
Scott, Brian Cameron. “Evaluation of Phenol Formaldehyde Resin Cure Rate.” 2005. Web. 11 Apr 2021.
Vancouver:
Scott BC. Evaluation of Phenol Formaldehyde Resin Cure Rate. [Internet] [Masters thesis]. Virginia Tech; 2005. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/33222.
Council of Science Editors:
Scott BC. Evaluation of Phenol Formaldehyde Resin Cure Rate. [Masters Thesis]. Virginia Tech; 2005. Available from: http://hdl.handle.net/10919/33222
Virginia Tech
4.
Kultikova, Elena V.
Structure and Properties Relationships of Densified Wood.
Degree: MS, Wood Science and Forest Products, 1999, Virginia Tech
URL: http://hdl.handle.net/10919/35810
► The objective of this research was to investigate the effect of applied compressive strain in various environments, on the strength and stiffness of compressed wood…
(more)
▼ The objective of this research was to investigate the effect of applied compressive strain in various environments, on the strength and stiffness of compressed wood samples. It is believed that transverse compression of wood at specific conditions of temperature and moisture will result in improved mechanical properties, which can be attributed to increased density and perhaps other physical or chemical changes.
Specimens of both mature and juvenile southern pine (Pinus taeda) and yellow-poplar (Liriodendron tulipifera) were compressed radially at three different temperature, and moisture content conditions relevant to the glass transition of wood.
Ultimate tensile stress and longitudinal modulus of elasticity were obtained by testing compressed, uncompressed and control samples in tension parallel-to-grain. Strain measurements were performed using laboratory-built clip-on strain gauge transducers. Results of the tensile tests have shown an increase in the ultimate tensile stress and modulus of elasticity after all densification treatments.
Scanning electron microscopy was employed for observing changes in cellular structure of densified wood. Existence of the cell wall fractures was evaluated using image processing and analysis software. Changes in cellular structure were correlated with the results of the tensile test.
Chemical composition of wood samples before and after desorption experiments was determined by acid hydrolysis followed by high performance liquid chromatography (HPLC). The results of the chemical analysis of the wood specimens did not reveal significant changes in chemical composition of wood when subjected to 160 °C, pure steam for up to 8 hours.
The results of this research will provide information about modifications that occur during wood compression and will result in better understanding of material behavior during the manufacture of wood-based composites. In the long run, modification of wood with inadequate mechanical properties can have a significant effect on the wood products industry. Low density and juvenile wood can be used in new high-performance wood-based composite materials instead of old-growth timber.
Advisors/Committee Members: Kamke, Frederick A. (committeechair), Frazier, Charles E. (committee member), Zink-Sharp, Audrey G. (committee member).
Subjects/Keywords: densified wood; stiffness; tensile strength
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APA (6th Edition):
Kultikova, E. V. (1999). Structure and Properties Relationships of Densified Wood. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35810
Chicago Manual of Style (16th Edition):
Kultikova, Elena V. “Structure and Properties Relationships of Densified Wood.” 1999. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/35810.
MLA Handbook (7th Edition):
Kultikova, Elena V. “Structure and Properties Relationships of Densified Wood.” 1999. Web. 11 Apr 2021.
Vancouver:
Kultikova EV. Structure and Properties Relationships of Densified Wood. [Internet] [Masters thesis]. Virginia Tech; 1999. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/35810.
Council of Science Editors:
Kultikova EV. Structure and Properties Relationships of Densified Wood. [Masters Thesis]. Virginia Tech; 1999. Available from: http://hdl.handle.net/10919/35810
Virginia Tech
5.
Shu, Jiang.
An Experiment Management Component for the WBCSim Problem Solving Environment.
Degree: MS, Computer Science, 2002, Virginia Tech
URL: http://hdl.handle.net/10919/36448
► This thesis describes a computing environment WBCSim and its experiment management component. WBCSim is a web-based simulation system used to increase the productivity of wood…
(more)
▼ This thesis describes a computing environment WBCSim and its experiment management component. WBCSim is a web-based simulation system used to increase the productivity of wood scientists conducting research on wood-based composite and material manufacturing processes. This experiment management component integrates a web-based graphical front end, server scripts, and a database management system to allow scientists to easily save, retrieve, and perform customized operations on experimental data. A detailed description of the system architecture and the experiment management component is presented, along with a typical scenario of usage.
Advisors/Committee Members: Watson, Layne T. (committeechair), Ramakrishnan, Naren (committee member), Kamke, Frederick A. (committee member).
Subjects/Keywords: Wood-based Composite Materials; Database Management; Computing Environment; Problem Solving Environment; Experiment Management
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APA (6th Edition):
Shu, J. (2002). An Experiment Management Component for the WBCSim Problem Solving Environment. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/36448
Chicago Manual of Style (16th Edition):
Shu, Jiang. “An Experiment Management Component for the WBCSim Problem Solving Environment.” 2002. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/36448.
MLA Handbook (7th Edition):
Shu, Jiang. “An Experiment Management Component for the WBCSim Problem Solving Environment.” 2002. Web. 11 Apr 2021.
Vancouver:
Shu J. An Experiment Management Component for the WBCSim Problem Solving Environment. [Internet] [Masters thesis]. Virginia Tech; 2002. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/36448.
Council of Science Editors:
Shu J. An Experiment Management Component for the WBCSim Problem Solving Environment. [Masters Thesis]. Virginia Tech; 2002. Available from: http://hdl.handle.net/10919/36448
Virginia Tech
6.
Crimm, Robert Prentiss.
Experimental apparatus for measuring moisture transfer in porous materials subject to relative humidity and temperature differences.
Degree: MS, Mechanical Engineering, 1992, Virginia Tech
URL: http://hdl.handle.net/10919/40614
Subjects/Keywords: Moisture; LD5655.V855 1992.C745
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APA (6th Edition):
Crimm, R. P. (1992). Experimental apparatus for measuring moisture transfer in porous materials subject to relative humidity and temperature differences. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/40614
Chicago Manual of Style (16th Edition):
Crimm, Robert Prentiss. “Experimental apparatus for measuring moisture transfer in porous materials subject to relative humidity and temperature differences.” 1992. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/40614.
MLA Handbook (7th Edition):
Crimm, Robert Prentiss. “Experimental apparatus for measuring moisture transfer in porous materials subject to relative humidity and temperature differences.” 1992. Web. 11 Apr 2021.
Vancouver:
Crimm RP. Experimental apparatus for measuring moisture transfer in porous materials subject to relative humidity and temperature differences. [Internet] [Masters thesis]. Virginia Tech; 1992. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/40614.
Council of Science Editors:
Crimm RP. Experimental apparatus for measuring moisture transfer in porous materials subject to relative humidity and temperature differences. [Masters Thesis]. Virginia Tech; 1992. Available from: http://hdl.handle.net/10919/40614
Virginia Tech
7.
Smith, Jeffrey Scott.
An Investigation of Nailed Connection Performance in a Cyclic Humidity Environment.
Degree: MS, Wood Science and Forest Products, 2004, Virginia Tech
URL: http://hdl.handle.net/10919/44136
► The effect of cyclic moisture infiltration on connections in light-frame wood buildings has received limited research attention. Specifically, the connections between wood-based sheathing materials (OSB,…
(more)
▼ The effect of cyclic moisture infiltration on connections in light-frame wood buildings has received limited research attention. Specifically, the connections between wood-based sheathing materials (OSB, plywood) and solid wood studs are of interest. A comprehensive understanding of connection performance will enhance structure and material design, thereby improving the overall integrity and robustness of light-frame structures.
The focus of this research project was to evaluate the strength and stiffness of wood-frame connections exposed to cyclic humidity conditioning. Nailed sheathing/stud connection samples were tested for lateral resistance following various periods of moisture exposure. Elastic stiffness, 5% offset yield load, maximum yield load, and failure yield were computed and analyzed using the data collected. The parameters were compared among connection specimens receiving either 0, 1, 5, 10, 15, 25, or 40 periods of cyclic moisture conditioning. In addition, the bearing resistances of the materials were investigated for application to the general dowel equations for calculating lateral connection values, the current basis for design of single dowel-type fastener connections between wood-based members. An x-ray density profilometer was used to observe the de-densification processes within the composite sheathing materials throughout the moisture conditioning regime.
Results indicated moderate to extreme changes in the performance of cycled connections involving lower density sheathing materials. Higher density sheathing materials performed favorably at each cycle test period. Comparisons to the yield model were similar to the control results, but usually differed as cycling increased.
Analysis of connection performance following cyclic moisture loading is a vital component in developing a holistic model for service-life prediction of nailed connections in light-frame residential construction.
Advisors/Committee Members: Loferski, Joseph R. (committeechair), Hindman, Daniel P. (committee member), Kamke, Frederick A. (committee member).
Subjects/Keywords: wood-based composites; connections; monotonic loading; durability; moisture cycling
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APA (6th Edition):
Smith, J. S. (2004). An Investigation of Nailed Connection Performance in a Cyclic Humidity Environment. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/44136
Chicago Manual of Style (16th Edition):
Smith, Jeffrey Scott. “An Investigation of Nailed Connection Performance in a Cyclic Humidity Environment.” 2004. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/44136.
MLA Handbook (7th Edition):
Smith, Jeffrey Scott. “An Investigation of Nailed Connection Performance in a Cyclic Humidity Environment.” 2004. Web. 11 Apr 2021.
Vancouver:
Smith JS. An Investigation of Nailed Connection Performance in a Cyclic Humidity Environment. [Internet] [Masters thesis]. Virginia Tech; 2004. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/44136.
Council of Science Editors:
Smith JS. An Investigation of Nailed Connection Performance in a Cyclic Humidity Environment. [Masters Thesis]. Virginia Tech; 2004. Available from: http://hdl.handle.net/10919/44136
Virginia Tech
8.
Kasal, Bohumil.
Behavior of wood under transverse compression.
Degree: MS, Wood Science and Forest Products, 1989, Virginia Tech
URL: http://hdl.handle.net/10919/40963
► The increasing demand on wood and wood products, and the simultaneously decreasing quality of wood as a raw material leads to the increasing significance…
(more)
▼ The increasing demand on wood and wood products, and the simultaneously decreasing quality of
wood as a raw material leads to the increasing significance of wood·based composites such as
particleboard or flakeboard. The resulting mechanical and physical properties are to the large extend
dictated by the densification of the wood component. To be able to predict the density of the
material, the behavior of structural elements must be known. A theory developed for rigid plastic
foams was modified and applied to the deformation of wood in transverse compression. A testing
procedure for high strain compression over a range of temperatures was developed. In addition, a
stochastic model for prediction of high strain behavior was developed. Wood of yellow poplar
(<i>Liriodendron tulipuera</i>) was used as the experimental material.
Advisors/Committee Members: Dillard, David A. (committee member), Skaar, Christian (committee member), Kamke, Frederick A. (committeecochair).
Subjects/Keywords: Wood - Compressed; LD5655.V855 1989.K373
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APA (6th Edition):
Kasal, B. (1989). Behavior of wood under transverse compression. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/40963
Chicago Manual of Style (16th Edition):
Kasal, Bohumil. “Behavior of wood under transverse compression.” 1989. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/40963.
MLA Handbook (7th Edition):
Kasal, Bohumil. “Behavior of wood under transverse compression.” 1989. Web. 11 Apr 2021.
Vancouver:
Kasal B. Behavior of wood under transverse compression. [Internet] [Masters thesis]. Virginia Tech; 1989. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/40963.
Council of Science Editors:
Kasal B. Behavior of wood under transverse compression. [Masters Thesis]. Virginia Tech; 1989. Available from: http://hdl.handle.net/10919/40963
Virginia Tech
9.
Johnson, Stephen E.
Response of mat conditions and flakeboard properties to steam- injection variables.
Degree: MS, Wood Science and Forest Products, 1990, Virginia Tech
URL: http://hdl.handle.net/10919/41747
► Mat conditions of temperature and gas pressure were measured in three locations for one conventional and four steam-injection press schedules used in the laboratory scale…
(more)
▼ Mat conditions of temperature and gas pressure were
measured in three locations for one conventional and four
steam-injection press schedules used in the laboratory scale
manufacture of aspen (Populus grandidentata and Populus
tremuloides) flakeboard. Two resins, phenol formaldehyde
and polymeric MDI, were used. Steam-injection press
schedules varied from low steam input to high steam input by
adjusting steam pressure, steam time, and the density range
for steam-injection during press closing. Steam-injection
rapidly raises mat core temperatures as compared to
conventional pressing. Temperature and gas pressure were
positively correlated with the amount of steam input.
Flakeboard strength and dimensional stability
properties were tested. Steam-injection pressing produced
panels with superior dimensional stability as compared to
conventional pressing. The high steam press schedule
produced internal bond and shear strengths equal to the
conventional press schedule for phenol formaldehyde. Medium
steam press schedules produced superior internal bond and
shear strengths to the conventional press schedule for
polymeric MDI. The conventional press schedule produced
superior static bending MOR strengths for both resins.
A fluorescence microscope was interfaced with a
digitizing image analysis system to measure resin
penetration area on flakes recovered from inside of the mat.
Wood anatomy was found to be the dominating factor in
creating high variablity in resin penetration area
measurements, as differences could not be detected due to
the press schedules or resin type.
Advisors/Committee Members: Kamke, Frederick A. (committeechair), White, Marshall S. (committee member), Wightman, James P. (committee member).
Subjects/Keywords: High-pressure; Steam; LD5655.V855 1990.J648
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APA (6th Edition):
Johnson, S. E. (1990). Response of mat conditions and flakeboard properties to steam- injection variables. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/41747
Chicago Manual of Style (16th Edition):
Johnson, Stephen E. “Response of mat conditions and flakeboard properties to steam- injection variables.” 1990. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/41747.
MLA Handbook (7th Edition):
Johnson, Stephen E. “Response of mat conditions and flakeboard properties to steam- injection variables.” 1990. Web. 11 Apr 2021.
Vancouver:
Johnson SE. Response of mat conditions and flakeboard properties to steam- injection variables. [Internet] [Masters thesis]. Virginia Tech; 1990. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/41747.
Council of Science Editors:
Johnson SE. Response of mat conditions and flakeboard properties to steam- injection variables. [Masters Thesis]. Virginia Tech; 1990. Available from: http://hdl.handle.net/10919/41747
Virginia Tech
10.
Hood, Jonathan Patrick.
Changes in Oriented Strandboard Permeability During Hot-Pressing.
Degree: MS, Wood Science and Forest Products, 2004, Virginia Tech
URL: http://hdl.handle.net/10919/10049
► Convective heat transfer during hot pressing in wood-based composite panel manufacturing is widely accepted as the most important means of heat transport for resin curing.…
(more)
▼ Convective heat transfer during hot pressing in wood-based composite panel manufacturing is widely accepted as the most important means of heat transport for resin curing. The rate of convective heat transfer to the panel core is controlled by its permeability. Permeability in the plane of the panel also controls the flow of vapor to the panel edges, thereby influencing the potential for panel "blowing".
This research considers how flake thickness, flake alignment and changing mat density during hot-pressing influences OSB mat permeability, through its thickness and in the plane of the panel. Some previous research exists but it fails to address the affects of horizontal and vertical density gradients as well as flake alignment.
An apparatus was designed to allow cold pressing of aligned flakes to desired densities while enabling permeability measurements through the mat thickness. An additional apparatus was designed to allow the measuring of permeability in the plane of the mat. These designs permitted permeability measurements in mats that had no vertical density gradient, allowing for the direct study of permeability versus density (compaction ratio).
Superficial permeability was determined using Darcy's law and for each sample, multiple readings were made at five different pressure differentials. Permeability through the mat thickness was highly dependent on compaction ratio and to a lesser extent flake thickness. As the compaction ratio is increased, the initial reduction in permeability is severe, once higher compaction ratios are achieved the reduction in permeability is less pronounced. Permeability decreased with decreasing flake thickness. Permeability in the plane of the mat decreases with increasing compaction ratio but in a less severe manner than through the mat thickness. In this case, the permeability-compaction ratio relationship appears linear in nature. Again, permeability decreases with decreasing flake thickness.
Advisors/Committee Members: Kamke, Frederick A. (committeechair), Zink-Sharp, Audrey G. (committee member), Loferski, Joseph R. (committee member).
Subjects/Keywords: density; Compaction Ratio; Darcy's law; Permeability
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APA (6th Edition):
Hood, J. P. (2004). Changes in Oriented Strandboard Permeability During Hot-Pressing. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/10049
Chicago Manual of Style (16th Edition):
Hood, Jonathan Patrick. “Changes in Oriented Strandboard Permeability During Hot-Pressing.” 2004. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/10049.
MLA Handbook (7th Edition):
Hood, Jonathan Patrick. “Changes in Oriented Strandboard Permeability During Hot-Pressing.” 2004. Web. 11 Apr 2021.
Vancouver:
Hood JP. Changes in Oriented Strandboard Permeability During Hot-Pressing. [Internet] [Masters thesis]. Virginia Tech; 2004. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/10049.
Council of Science Editors:
Hood JP. Changes in Oriented Strandboard Permeability During Hot-Pressing. [Masters Thesis]. Virginia Tech; 2004. Available from: http://hdl.handle.net/10919/10049
Virginia Tech
11.
Jennings, Jessica D.
Investigating the Surface Energy and Bond Performance of Compression Densified Wood.
Degree: MS, Wood Science and Forest Products, 1997, Virginia Tech
URL: http://hdl.handle.net/10919/10150
► The bond performance and surface energy of hygro-thermal compression densified wood were studied using comparisons to hygro-thermally treated and control yellow-poplar (Liriodendron tulipifera). Bond performance…
(more)
▼ The bond performance and surface energy of hygro-thermal compression densified wood were studied using comparisons to hygro-thermally treated and control yellow-poplar (Liriodendron tulipifera).
Bond performance was studied using opening mode double cantilever beam fracture testing and cyclic boiling of one half of all fracture samples. Phenol formaldehyde film (PF-film) and polymeric diphenylmethane diisocyanate (pMDI) were the two different adhesives used to bond fracture samples. Hygro-thermal samples bonded with PF-film had significantly higher fracture toughness than control samples, while no difference was found for densified samples. Densified samples bonded with pMDI had significantly higher fracture toughness than control samples while no change was seen for hygro-thermal samples. Boil cycling reduced fracture toughness of hygro-thermal fracture samples only, irrespective of adhesive type.
Surface energy was studied using sessile drop contact angle measurement and the Chang model of acid-base, surface energy component calculation. Water, glycerol, formamide, ethylene glycol, and -Bromonapthalene were used as probe liquids. Densified and hygro-thermally treated yellow-poplar had significantly higher contact angles than control samples. The contact angle trends for densified and hygro-thermally treated wood were found to be the same. Total surface energy as well as the polar and acid components of surface energy decreased with hygro-thermal treatment. The dispersive and base components of surface energy increased with hygro-thermal treatment.
Advisors/Committee Members: Zink-Sharp, Audrey G. (committeechair), Kamke, Frederick A. (committee member), Frazier, Charles E. (committee member).
Subjects/Keywords: bond durability; fracture mechanics; surface energy; densified wood
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APA (6th Edition):
Jennings, J. D. (1997). Investigating the Surface Energy and Bond Performance of Compression Densified Wood. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/10150
Chicago Manual of Style (16th Edition):
Jennings, Jessica D. “Investigating the Surface Energy and Bond Performance of Compression Densified Wood.” 1997. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/10150.
MLA Handbook (7th Edition):
Jennings, Jessica D. “Investigating the Surface Energy and Bond Performance of Compression Densified Wood.” 1997. Web. 11 Apr 2021.
Vancouver:
Jennings JD. Investigating the Surface Energy and Bond Performance of Compression Densified Wood. [Internet] [Masters thesis]. Virginia Tech; 1997. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/10150.
Council of Science Editors:
Jennings JD. Investigating the Surface Energy and Bond Performance of Compression Densified Wood. [Masters Thesis]. Virginia Tech; 1997. Available from: http://hdl.handle.net/10919/10150
Virginia Tech
12.
Cao, Jiqiang.
The development of a durability procedure for pallets with structural panel decking.
Degree: MS, Forest Products, 1993, Virginia Tech
URL: http://hdl.handle.net/10919/44597
► The Pallet Design System (PDS) is a widely accepted engineering procedure for comparing the performance of competing pallet designs. As part of a new version…
(more)
▼ The Pallet Design System (PDS) is a widely accepted engineering procedure for comparing the performance of competing pallet designs. As part of a new version of the PDS, the objective of this study was to develop a durability model for pallets with structural panel decking.
An accelerated rough material handling test system, "the VPI unit-load material
handling FasTrack" , was developed to simulate pallets used in the unit-load material handling environments. 100 pallets representing 14 different designs were tested in the "FasTrack." Damages to these pallets were recorded after each test cycle. A procedure relating damage to repair cost was developed. The effect of panel-deck pallet design on the resistance to damage was evaluated in terms of the total number of damaged parts and average damage
cost or repair cost. Test results indicate that panel grade and type, species of related wood parts, size of stringer and deckboards, joints, and pallet configurations affect the resistance of panel deck pallet to damage.
The plots of average total damage cost, Cu adjusted for repair as a function of test cycle, U, fit the equation: Ct = aU - 1. The equation provided good fits to all the pallet designs tested. Using the initial purchase prices, the average cost and the economic life were calculated for all the pallet designs.
The VPI "FasTrack" was calibrated based on the number of physical handlings andthe amortized life. Three typical in-field handling environments were compared with the VPI "FasTrack". It concluded that the 30-cycle test period in the VPI "FasTrack" simulates between 2 to 5 years of field uses depending on the field handling system being simulated. Thirty Canadian Pallet Council (CPC) pallets with known 7 years of amortized life in the field were tested in the VPI "FasTrack". The 30-cycle test in the VPI system simulated 6 years of use in the similar handling environment of the CPC pallet used by the grocery
industry in Canada.
The average total damage costs for different pallet designs were related to pallet structural characteristics using multivariate regression analysis. The shear resistance through the thickness of the top panel deck, bottom deck flexural strength, pallet flexural strength, fastener withdrawal resistance, and pallet configuration were used to predict the total damage cost. A multiple regression model was developed. The model was verified by comparing the predicted values with the tested values of 12 panel deck pallets representing 2 designs.
The results indicated that the model is reliable for the future predictions.
Advisors/Committee Members: White, Marshall S. (committeechair), Loferski, Joseph R. (committeechair), Kamke, Frederick A. (committee member).
Subjects/Keywords: storage; Pallets (Shipping; etc.); LD5655.V855 1993.C37
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APA (6th Edition):
Cao, J. (1993). The development of a durability procedure for pallets with structural panel decking. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/44597
Chicago Manual of Style (16th Edition):
Cao, Jiqiang. “The development of a durability procedure for pallets with structural panel decking.” 1993. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/44597.
MLA Handbook (7th Edition):
Cao, Jiqiang. “The development of a durability procedure for pallets with structural panel decking.” 1993. Web. 11 Apr 2021.
Vancouver:
Cao J. The development of a durability procedure for pallets with structural panel decking. [Internet] [Masters thesis]. Virginia Tech; 1993. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/44597.
Council of Science Editors:
Cao J. The development of a durability procedure for pallets with structural panel decking. [Masters Thesis]. Virginia Tech; 1993. Available from: http://hdl.handle.net/10919/44597
Virginia Tech
13.
Scoville, Christopher R.
Characterizing the Durability of PF and pMDI Adhesive Wood Composites Through Fracture Testing.
Degree: MS, Wood Science and Forest Products, 2001, Virginia Tech
URL: http://hdl.handle.net/10919/35353
► The increased use of wood composites in building materials results in a need for a better understanding of wood adhesion. The effects of water and…
(more)
▼ The increased use of wood composites in building materials results in a need for a better understanding of wood adhesion. The effects of water and temperature exposure on the durability of wood products were assessed using the double-cantilever beam (DCB) method of fracture testing. The relative durability of phenol-formaldehyde (PF) and isocyanate (pMDI) adhesives was compared using a 2-hour boil test and an environmental test. The feasibility of using oriented strandboard (OSB), oriented strand lumber (OSL) and parallel strand lumber (PSL) for the DCB fracture method was assessed. The fracture resistance of PF was reduced significantly by the aging exposures. The fracture resistance of pMDI did not decrease after the 2-hour boil test. The DCB fracture method was shown to be useful with a square-grooved machined specimen using OSB and OSL.
Advisors/Committee Members: Loferski, Joseph R. (committeechair), Kamke, Frederick A. (committee member), Frazier, Charles E. (committee member).
Subjects/Keywords: durability; accelerated exposure; fracture testing; Wood composites
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APA (6th Edition):
Scoville, C. R. (2001). Characterizing the Durability of PF and pMDI Adhesive Wood Composites Through Fracture Testing. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35353
Chicago Manual of Style (16th Edition):
Scoville, Christopher R. “Characterizing the Durability of PF and pMDI Adhesive Wood Composites Through Fracture Testing.” 2001. Masters Thesis, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/35353.
MLA Handbook (7th Edition):
Scoville, Christopher R. “Characterizing the Durability of PF and pMDI Adhesive Wood Composites Through Fracture Testing.” 2001. Web. 11 Apr 2021.
Vancouver:
Scoville CR. Characterizing the Durability of PF and pMDI Adhesive Wood Composites Through Fracture Testing. [Internet] [Masters thesis]. Virginia Tech; 2001. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/35353.
Council of Science Editors:
Scoville CR. Characterizing the Durability of PF and pMDI Adhesive Wood Composites Through Fracture Testing. [Masters Thesis]. Virginia Tech; 2001. Available from: http://hdl.handle.net/10919/35353
Virginia Tech
14.
Lang, Elemer M.
Modeling the behavior of wood-based composite sheathing under hygrothermal load.
Degree: PhD, Wood Science and Forest Products, 1993, Virginia Tech
URL: http://hdl.handle.net/10919/40035
► In light-frame residential construction wood-based composite panels used externally or internally are exposed to relative humidity and/or temperature changes. The subsequent moisture content change of…
(more)
▼ In light-frame residential construction wood-based composite panels used externally or internally are exposed to relative humidity and/or temperature changes. The subsequent moisture content change of the panels will result in two types of deformations as follows: 1. elastic deformation of the panel due to the constraint, 2. warpage of the panel due to the unbalanced expansion of the layers. Such deformations can cause unacceptable serviceability problems in light-frame wood construction.
A model was developed to predict quantitatively the global deflection of wood-based composite panels exposed to relative humidity changes. The model was based on the constitutive relationship of the Classical Lamination Theory and the thermal stress analogy in composites. As an alternative solution, the applicability of the eccentrically loaded column formula was evaluated.
The developed models were experimentally validated for OSB and plywood sheathing. Test variables included the panel type, exposure (symmetric and non-symmetric MC gradient) and specimen configuration (single span, multiple span). The comparison of measured and predicted deflections are presented. The important elastic and hygroscopic material properties were acquired through testing. Statistical analyses of test results are discussed.
The uncertainty analysis was used to make statistical inference comparing the means of measured deflection to the uncertainty interval of predictions. Good agreement between predicted and measured deflections was found for single span test structures. Also, for double span structures the models predicted the experimental response fairly veil. Uncertainties in Me measurements made the prediction less reliable when symmetric moisture content gradient developed during the exposure. Due to its lower variability in material properties, the response of OSB sheathing to moisture content changes is more predictable.
Advisors/Committee Members: Dolan, James Daniel (committeechair), Ifju, Geza (committee member), Kamke, Frederick A. (committee member), Woeste, Frank E. (committee member).
Subjects/Keywords: Composite construction.; Plywood.; Wooden-frame houses Thermal properties.; Hygrothermoelasticity.; LD5655.V856 1993.L366
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APA (6th Edition):
Lang, E. M. (1993). Modeling the behavior of wood-based composite sheathing under hygrothermal load. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/40035
Chicago Manual of Style (16th Edition):
Lang, Elemer M. “Modeling the behavior of wood-based composite sheathing under hygrothermal load.” 1993. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/40035.
MLA Handbook (7th Edition):
Lang, Elemer M. “Modeling the behavior of wood-based composite sheathing under hygrothermal load.” 1993. Web. 11 Apr 2021.
Vancouver:
Lang EM. Modeling the behavior of wood-based composite sheathing under hygrothermal load. [Internet] [Doctoral dissertation]. Virginia Tech; 1993. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/40035.
Council of Science Editors:
Lang EM. Modeling the behavior of wood-based composite sheathing under hygrothermal load. [Doctoral Dissertation]. Virginia Tech; 1993. Available from: http://hdl.handle.net/10919/40035
Virginia Tech
15.
Chen, Zhangjing.
Primary Driving Force in Wood Vacuum Drying.
Degree: PhD, Wood Science and Forest Products, 1997, Virginia Tech
URL: http://hdl.handle.net/10919/26255
► The objective of this research based on both the theory and experimentation was to prove that the total pressure difference is the primary driving force…
(more)
▼ The objective of this research based on both the theory and experimentation was to prove that the total pressure difference is the primary driving force during the vacuum drying. The theoretical drying rates of diffusion, free water bulk flow and water vapor bulk flow were calculated and compared. The concept of equilibrium moisture content under the vacuum was developed. The theoretical maximum moisture content drop in one cycle was calculated using energy balance. The model was developed for the vacuum drying to understand the mechanism of the vacuum drying including the boiling front and its movement.
To evaluate the effect of the sample size on the drying rate, four different thicknesses (1, 1.5, 2, 2.5 inches) and three different lengths (5, 10, 15 inches) were used. In the cyclic drying, the specimens were heated to the 60 C. The vacuum was pulled to about 18 mm Hg. The vacuum pump was kept running for 140 minutes. It was found that in cyclic vacuum drying, drying rate was not affected by the thickness. However, it was affected by the length. The cyclic drying curve consisted of two distinct parts. The fast drying period lasted about 10 to 20 minutes. The slow drying period occurred next when the pressure inside wood got close to the ambient pressure.
In end grain vacuum drying, the specimens were coated with wax, wrapped in the plastic film and inserted into a rubber tube to prevent the moisture loss from the side surfaces during drying. The specimen size was 1×1×10 inches. Red oak and white oak were sealed and dried in both cyclic and continuous vacuum drying. The results showed that sealed specimens dried almost as fast as unsealed specimen. There was little moisture loss from the side surfaces. There was a moisture gradient along the length in both cyclic drying and continuous vacuum drying.
Red oak specimens of 2.5×1.5×10 inches were used to study the boiling front in the vacuum drying. In order to detect the boiling phenomenon, the saturation pressures were calculated and were compared with the pressures at the same time and the same location. Boiling occurred during drying and the boiling front retreated to the center of wood as drying proceeded. The retreating speed depended on the heat supply and the permeability.
Vacuum drying at room temperature was investigated. The specimens were dried at 20 C and pressure near 18 mm Hg. The results showed that wood can be vacuum dried at room temperature with little or no degrade at a reasonable drying rate.
All experimental results support the objective of this study that the primary driving force is the total pressure difference.
Advisors/Committee Members: Lamb, Fred M. (committeechair), White, Marshall S. (committee member), Skaar, Christian (committee member), Nelson, Douglas J. (committee member), Kamke, Frederick A. (committee member).
Subjects/Keywords: driving force; wood vacuum drying; boiling front; room temperature drying; end grain drying
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APA (6th Edition):
Chen, Z. (1997). Primary Driving Force in Wood Vacuum Drying. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/26255
Chicago Manual of Style (16th Edition):
Chen, Zhangjing. “Primary Driving Force in Wood Vacuum Drying.” 1997. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/26255.
MLA Handbook (7th Edition):
Chen, Zhangjing. “Primary Driving Force in Wood Vacuum Drying.” 1997. Web. 11 Apr 2021.
Vancouver:
Chen Z. Primary Driving Force in Wood Vacuum Drying. [Internet] [Doctoral dissertation]. Virginia Tech; 1997. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/26255.
Council of Science Editors:
Chen Z. Primary Driving Force in Wood Vacuum Drying. [Doctoral Dissertation]. Virginia Tech; 1997. Available from: http://hdl.handle.net/10919/26255
Virginia Tech
16.
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
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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
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
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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.
Deomano, Edgar Dela Cruz.
Mechanism of Flake Drying and Its Correlation to Quality.
Degree: PhD, Wood Science and Forest Products, 2001, Virginia Tech
URL: http://hdl.handle.net/10919/28452
► This research focuses on experimental investigations of the drying and bending properties of wood flakes. Three species (southern yellow pine, sweetgum, and yellow-poplar) were tested.…
(more)
▼ This research focuses on experimental investigations of the drying and bending properties of wood flakes. Three species (southern yellow pine, sweetgum, and yellow-poplar) were tested. Experiments on flake drying and effect of flake properties (cutting direction and dimension) and an external factor (temperature) were used to evaluate the flake drying process. Drying experiments were conducted using a convection oven. Bending properties of dried flakes were also measured. Modulus of elasticity (MOE), modulus of rupture (MOR), and strength at proportional limit (SPL) of flakes were measured based on Methods of Testing Small Clear Specimens of Timber (ASTM D143-94) using a miniature material tester.
The drying curve was characterized by a second-order/quadratic equation. This equation was then differentiated to get the drying rate curve. Observation on drying and drying rate curves revealed that the rate of moisture loss consists of two falling rate periods; no constant rate drying period was observed. First falling rate drying period is controlled by convective heat transfer. Bound water diffusion controls the second falling rate drying period.
Species, cutting direction, dimension, and temperature were found to have significant effect on drying rate of wood flakes. Southern yellow pine has the fastest drying rate followed by sweetgum then yellow-poplar. Differences in drying rate between species were attributed to differences in specific gravity and other factors. Radially-cut specimens have a slower drying rate than tangentially-cut specimens. There were also significant differences in drying rate between the four different flake dimensions. Thickness was found to be the more sensitive parameter in terms of dimensions. As expected, drying temperature also had highly significant effect on drying rate. An increasing trend in drying rate was observed as drying temperature increased.
Simulation of flake drying using a numerical model yielded a different result. Simulated flake drying has two drying periods: a constant rate and falling rate. Moisture of the flake decreases constantly and surface temperature increases rapidly to boiling point and remains there in the constant rate drying period. During the falling rate period, rate of moisture transport is limited by the ability of water to diffuse through wood and flake temperature starts to rise.
Bending properties were found to vary between and within the three species. Southern yellow pine had the lowest bending stiffness and strength followed by sweetgum while yellow-poplar had the highest bending properties. Radially-cut specimens were found to have lower MOE, MOR, and SPL than tangentially-cut specimens. Drying temperature was also found to have a significant effect on bending stiffness and strength. A decreasing trend in bending properties was observed when drying temperature was increased.
Advisors/Committee Members: Zink-Sharp, Audrey G. (committeechair), Kamke, Frederick A. (committee member), Hinkelmann, Klaus H. (committee member), Youngs, Robert L. (committee member), Lamb, Fred M. (committee member).
Subjects/Keywords: Small and thin wood; Drying Kinetics
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APA (6th Edition):
Deomano, E. D. C. (2001). Mechanism of Flake Drying and Its Correlation to Quality. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/28452
Chicago Manual of Style (16th Edition):
Deomano, Edgar Dela Cruz. “Mechanism of Flake Drying and Its Correlation to Quality.” 2001. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/28452.
MLA Handbook (7th Edition):
Deomano, Edgar Dela Cruz. “Mechanism of Flake Drying and Its Correlation to Quality.” 2001. Web. 11 Apr 2021.
Vancouver:
Deomano EDC. Mechanism of Flake Drying and Its Correlation to Quality. [Internet] [Doctoral dissertation]. Virginia Tech; 2001. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/28452.
Council of Science Editors:
Deomano EDC. Mechanism of Flake Drying and Its Correlation to Quality. [Doctoral Dissertation]. Virginia Tech; 2001. Available from: http://hdl.handle.net/10919/28452
Virginia Tech
19.
Shu, Jiang.
Experiment Management for the Problem Solving Environment WBCSim.
Degree: PhD, Computer Science, 2009, Virginia Tech
URL: http://hdl.handle.net/10919/28713
► A problem solving environment (PSE) is a computational system that provides a complete and convenient set of high level tools for solving problems from a…
(more)
▼ A problem solving environment (PSE) is a computational system that provides
a complete and convenient set of high level tools for solving problems
from a specific domain. This thesis takes an in-depth look at the experiment
management aspect of PSEs, which can be divided into three levels: 1) data
management, 2) change management, and 3) execution management. At the data
management level, anything related to an experiment (computer simulation)
should be stored and documented. A database management system can be used
to store the simulation runs for a PSE. Then various high level interfaces
can be provided to allow users to save, retrieve, search, and compare these
simulation runs. At the change management level, a scientist should only
focus on how to solve a problem in the experiment domain. Aside from
running experiments, a scientist may only consider how to define a new
model, how to modify an existing model, and how to interpret an experiment
result. By using XML to describe a simulation model and unify various
implementation layers, changing an existing model in a PSE can be intuitive
and fast. At the execution management level, how an experiment is executed
is the main concern. By providing a computational steering capability, a
scientist can pause, examine, and compare the intermediate results from a
simulation. Contrasted with the traditional way of running a lengthy
simulation to see the result at the end, computational steering can leverage
the user's expert knowledge on the fly (during the simulation run) and
provide new insights and new product design opportunities. This thesis
illustrates these concepts and implementation by using WBCSim as an example.
WBCSim is a PSE that increases the productivity of wood scientists conducting
research on wood-based composite materials and manufacturing processes.
It integrates Fortran 90 simulation codes with a Web based graphical front
end, an optimization tool, and various visualization tools. The WBCSim
project was begun in 1997 with support from United States Department of
Agriculture, Department of Energy, and
Virginia Tech. It has since been
used by students in several wood science classes, by graduate students and
faculty, and by researchers at several forest products companies. WBCSim
also serves as a test bed for the design, construction, and evaluation of
useful, production quality PSEs.
Advisors/Committee Members: Watson, Layne T. (committeechair), Kamke, Frederick A. (committee member), Ramakrishnan, Naren (committee member), Shaffer, Clifford A. (committee member), North, Christopher L. (committee member).
Subjects/Keywords: problem solving environment; XML; computational steering; computing environment; wood-based composite materials; database management; visualization; optimization; experiment management
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APA (6th Edition):
Shu, J. (2009). Experiment Management for the Problem Solving Environment WBCSim. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/28713
Chicago Manual of Style (16th Edition):
Shu, Jiang. “Experiment Management for the Problem Solving Environment WBCSim.” 2009. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/28713.
MLA Handbook (7th Edition):
Shu, Jiang. “Experiment Management for the Problem Solving Environment WBCSim.” 2009. Web. 11 Apr 2021.
Vancouver:
Shu J. Experiment Management for the Problem Solving Environment WBCSim. [Internet] [Doctoral dissertation]. Virginia Tech; 2009. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/28713.
Council of Science Editors:
Shu J. Experiment Management for the Problem Solving Environment WBCSim. [Doctoral Dissertation]. Virginia Tech; 2009. Available from: http://hdl.handle.net/10919/28713
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
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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.
Ahmad, Mansur.
Analysis of Calcutta bamboo for structural composite materials.
Degree: PhD, Wood Science and Forest Products, 2000, Virginia Tech
URL: http://hdl.handle.net/10919/28742
► Land use issues have dramatically changed the timber supply outlook for our nation's forest products industry. Since demand for wood products shows no sign of…
(more)
▼ Land use issues have dramatically changed the timber supply outlook for our nation's forest products industry. Since demand for wood products shows no sign of abating, alternative products must be developed. Bamboo is a very promising alternative raw material for the manufacture of structural composite products. It is fast growing, economical, renewable and abundant throughout the world. Bamboo has physical and mechanical properties that are comparable to many commercial timber species, and thus, may easily be processed using existing technology from the wood-based composites industry. Bamboo can be cultivated in the U.S., and thus has the potential to relieve some of the harvesting pressure from our nation's forestlands. However, the use of specific bamboo species for structural composite products will require a thorough investigation of the material as well as its interaction with other components. Thus, the primary objective of this dissertation is to determine the properties of Calcutta bamboo and its interaction with adhesives. The properties investigated were relative density, dimensional stability, equilibrium moisture content, bending strength and stiffness, tensile strength, pH, buffer capacity, wettability and the adhesive penetration. In addition to this, a prototype bamboo parallel strip lumber (BPSL) was manufactured and tested for its physical and mechanical properties. The relationships among the properties of Calcutta bamboo and the prototype bamboo composite were also investigated. As the result of these investigations, it is concluded that Calcutta bamboo is technically a suitable raw material for structural composite products. This result may also be applicable for the utilization of other bamboo species, thus aiding companies in decisions regarding investment in bamboo plantations and manufacturing facilities in the U.S, Malaysia and other parts of the world. The primary benefits from this research may be the development of new products to serve growing markets, and thereby relieving some of the pressure to harvest forestlands.
Advisors/Committee Members: Kamke, Frederick A. (committeechair), Zink-Sharp, Audrey G. (committee member), Lamb, Fred M. (committee member), Dolan, James Daniel (committee member), Deisenroth, Michael P. (committee member).
Subjects/Keywords: Adhesive penetration; Physical and mechanical properties; pMDI; Surface properties; Phenol formaldehyde; Bamboo parallel strip lumber.
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APA (6th Edition):
Ahmad, M. (2000). Analysis of Calcutta bamboo for structural composite materials. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/28742
Chicago Manual of Style (16th Edition):
Ahmad, Mansur. “Analysis of Calcutta bamboo for structural composite materials.” 2000. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/28742.
MLA Handbook (7th Edition):
Ahmad, Mansur. “Analysis of Calcutta bamboo for structural composite materials.” 2000. Web. 11 Apr 2021.
Vancouver:
Ahmad M. Analysis of Calcutta bamboo for structural composite materials. [Internet] [Doctoral dissertation]. Virginia Tech; 2000. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/28742.
Council of Science Editors:
Ahmad M. Analysis of Calcutta bamboo for structural composite materials. [Doctoral Dissertation]. Virginia Tech; 2000. Available from: http://hdl.handle.net/10919/28742
Virginia Tech
22.
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
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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
23.
Gu, Hongmei.
Structure Based, Two-dimensional, Anisotropic, Transient Heat Conduction model for Wood.
Degree: PhD, Wood Science and Forest Products, 2001, Virginia Tech
URL: http://hdl.handle.net/10919/28938
► The importance of precise values for the parameters used in heat and mass transfer models has been demonstrated by many research studies. Thermal conductivity values…
(more)
▼ The importance of precise values for the parameters used in heat and mass transfer models has been demonstrated by many research studies. Thermal conductivity values used in previous models are usually empirical and fluctuate. Theoretical analysis and estimations of wood thermal conductivities in the radial and tangential directions were conducted with the geometric models built up from the macro- and micro-structure observations. Theoretically, thermal conductivity in the radial direction is about 1.5 to 2.5 times of the tangential direction for softwood species with moisture content (MC) below Fiber Saturation Point (FSP). When MC is over the FSP, tangential radial thermal conductivity both increase dramatically and are linear function of MC. The two thermal conductivity values are close with a ratio of near one estimated by the model for MC above the FPS. In hardwood species, radial thermal conductivity estimated by the model is 1.5 times of the tangential thermal conductivity. Validation tests for model estimations of thermal conductivities in the radial and tangential directions for three wood species showed the reliability of the geometric models developed in this project. Correlations between the wood thermal conductivity and structure parameters, such as latewood percentage and cell wall percentage, were examined. Linear relationships for the thermal conductivity and average temperature in wood were established in both radial and tangential directions of three wood species.
A two-dimensional transient heat conduction model was developed utilizing thermal conductivity values derived from geometric models. The anisotropic material property affect on heat transport in radial and tangential directions was discussed using an assumed situation. The simulation run showed slightly faster heat flow in the radial direction than in the tangential direction due to higher thermal conductivity in the radial direction. Validation tests on practical wood blocks showed the 2D model with the use of theoretical thermal conductivity values can predict good temperature distribution in wood during the heating process. However, in the practical wood samples with curved rings on the cross section, no significant difference was found in the two transverse directions.
Mathematica software was introduced in this study for the intense and complicated math calculations and model programming. Mathematica was found to be a powerful technique for solving sophisticated math problems. It had abundant and flexible plotting options for providing optimized presentations for the results. These advantages make Mathematica popular for engineering modeling research.
Advisors/Committee Members: Zink-Sharp, Audrey G. (committeechair), Youngs, Robert L. (committee member), Diller, Thomas E. (committee member), Lamb, Fred M. (committee member), Kamke, Frederick A. (committee member).
Subjects/Keywords: Geometric modeling; Finite difference; numerical model; Thermal conductivity; Anatomical structure
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APA (6th Edition):
Gu, H. (2001). Structure Based, Two-dimensional, Anisotropic, Transient Heat Conduction model for Wood. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/28938
Chicago Manual of Style (16th Edition):
Gu, Hongmei. “Structure Based, Two-dimensional, Anisotropic, Transient Heat Conduction model for Wood.” 2001. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/28938.
MLA Handbook (7th Edition):
Gu, Hongmei. “Structure Based, Two-dimensional, Anisotropic, Transient Heat Conduction model for Wood.” 2001. Web. 11 Apr 2021.
Vancouver:
Gu H. Structure Based, Two-dimensional, Anisotropic, Transient Heat Conduction model for Wood. [Internet] [Doctoral dissertation]. Virginia Tech; 2001. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/28938.
Council of Science Editors:
Gu H. Structure Based, Two-dimensional, Anisotropic, Transient Heat Conduction model for Wood. [Doctoral Dissertation]. Virginia Tech; 2001. Available from: http://hdl.handle.net/10919/28938
Virginia Tech
24.
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
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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
25.
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
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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
26.
Brown, Nicole Robitaille.
Understanding the Role of N-Methylolacrylamide (Nma) Distribution in Poly(Vinyl Acetate) Latex Adhesives.
Degree: PhD, Wood Science and Forest Products, 2003, Virginia Tech
URL: http://hdl.handle.net/10919/26446
► This work addresses the distribution of N-methylolacrylamide (NMA) units in crosslinking poly(vinyl acetate) (PVAc) adhesives. In this case, distribution refers to the three potential locations…
(more)
▼ This work addresses the distribution of N-methylolacrylamide (NMA) units in crosslinking poly(vinyl acetate) (PVAc) adhesives. In this case, distribution refers to the three potential locations of polymerized NMA units in a latex: the water-phase, the surface of polymer particles, and the core of the polymer particles. The objective is to identify the distribution of NMA in three latices and to determine whether NMA distribution correlates with durability related performance. NMA distribution was studied via a series of variable temperature solution NMR experiments, while the durability-related performance was studied via mode I fracture mechanics tests.
Studying the distribution of NMA required the use of isotopically labeled NMA. Both 15N-NMA and 13C, 15N-NMA were synthesized. Three NMA/vinyl acetate (VAc) latices were prepared. The NMA feed strategy was varied during each of the three emulsion copolymerizations. Latex characterization methods including differential scanning calorimetry (DSC), rheometry, particle size analysis, and scanning electron microscopy (SEM) were used to study the three latices.
The solution NMR method to identify NMA distribution was performed on untreated latices and on washed latices. Washing techniques included membrane dialysis and centrifugation. Results revealed that the three latices had different NMA distributions, and that the distributions were related to the expected differences in microstructure. Latex 3 had ~ 80% core-NMA, while Latex 2 had ~ 80% surface-NMA. Latex 1 had a high proportion of surface-NMA (~60%), but also had the highest proportion of water-phase NMA (~ 20%). This high proportion of water-phase NMA could be responsible for the unique morphology Latex 1 exhibited in SEM studies.
Mode I opening fracture mechanics studies were used to study adhesive performance. Specimens were analyzed after exposure to accelerated aging treatments. Latex 2 and Latex 3 exhibited very similar results, despite having very different NMA distributions. All three latices showed good durability related performance. In Latex 2 and Latex 3, the critical strain energy release rates (Gc) after accelerated aging treatments were statistically the same as the Gc of the control specimens. The most interesting finding was that the Latex 1 Gc values were significantly higher after accelerated aging. Latex 1 also had the highest proportion of water-phase NMA. Bondline images and SEM micrographs both indicated that the integrity of Latex 1 was least affected by the accelerated aging treatments.
Advisors/Committee Members: Gibson, Harry W. (committee member), Dillard, John G. (committee member), Kamke, Frederick A. (committee member), Frazier, Charles E. (committeecochair), Loferski, Joseph R. (committeecochair).
Subjects/Keywords: N-methylolacrylamide; NMA; 13C 15N-NMA; 15N-NMA; poly(vinyl acetate); PVAc; emulsion polymerization; monomer distribution; durability; solution NMR; fracture mechanics; wood adhesives; 13C-NMA
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APA (6th Edition):
Brown, N. R. (2003). Understanding the Role of N-Methylolacrylamide (Nma) Distribution in Poly(Vinyl Acetate) Latex Adhesives. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/26446
Chicago Manual of Style (16th Edition):
Brown, Nicole Robitaille. “Understanding the Role of N-Methylolacrylamide (Nma) Distribution in Poly(Vinyl Acetate) Latex Adhesives.” 2003. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/26446.
MLA Handbook (7th Edition):
Brown, Nicole Robitaille. “Understanding the Role of N-Methylolacrylamide (Nma) Distribution in Poly(Vinyl Acetate) Latex Adhesives.” 2003. Web. 11 Apr 2021.
Vancouver:
Brown NR. Understanding the Role of N-Methylolacrylamide (Nma) Distribution in Poly(Vinyl Acetate) Latex Adhesives. [Internet] [Doctoral dissertation]. Virginia Tech; 2003. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/26446.
Council of Science Editors:
Brown NR. Understanding the Role of N-Methylolacrylamide (Nma) Distribution in Poly(Vinyl Acetate) Latex Adhesives. [Doctoral Dissertation]. Virginia Tech; 2003. Available from: http://hdl.handle.net/10919/26446
Virginia Tech
27.
Zombori, Balazs Gergely.
Modeling the Transient Effects during the Hot-Pressing of Wood-Based Composites.
Degree: PhD, Wood Science and Forest Products, 2001, Virginia Tech
URL: http://hdl.handle.net/10919/27299
► A numerical model based on fundamental engineering principles was developed and validated to establish a relationship between process parameters and the final properties of woodbased…
(more)
▼ A numerical model based on fundamental engineering principles was developed and validated to establish a relationship between process parameters and the final properties of woodbased composite boards. The model simulates the mat formation, then compresses the reconstituted mat to its final thickness in a virtual press. The number of interacting variables during the hot-compression process is prohibitively large to assess a wide variety of data by experimental means. Therefore, the main advantage of the model based approach that the effect of the hot-compression parameters on the final properties of wood-based composite boards can be monitored without extensive experimentation.
The mat formation part of the model is based on the Monte Carlo simulation technique to reproduce the spatial structure of the mat. The dimensions and the density of each flake are considered as random variables in the model, which follow certain probability density distributions. The parameters of these distributions are derived from data collected on industrial flakes by using an image analysis technique. The model can simulate the structure of a threelayer oriented strandboard (OSB) mat as well as the structure of random fiber networks. A grid is superimposed on the simulated mat and the number of flakes, the thickness, and the density of the mat at each grid point are computed. Additionally, the model predicts the change in several void volume fractions within the mat and the contact area between the flakes during consolidation. The void volume fractions are directly related to the physical properties of the mat, such as thermal conductivity, diffusivity, and permeability, and the contact area is an indicator of the effectively bonded area within the mat.
The heat and mass transfer part of the model predicts the change of air content, moisture content, and temperature at designated mesh points in the cross section of the mat during the hotcompression. The water content is subdivided into vapor and bound water components. The free water component is not considered in the model due to the low (typically 6-7 %) initial moisture content of the flakes. The gas phase (air and vapor) moves by bulk flow and diffusion, while the bound water only moves by diffusion across the mat. The heat flow occurs by conduction and convection. The spatial derivatives of the resulting coupled partial differential equations are discretized by finite differences. The resulting ordinary differential equation in time is solved by a differential-algebraic system solver (DDASSL). The internal environment within the mat can be predicted among different initial and boundary conditions by this part of the hot-compression model.
In the next phase of the research, the viscoelastic (time, temperature, and moisture dependent) response of the flakes was modeled using the time-temperature-moisture superposition principle of polymers. A master curve was created from data available in the literature, which describes the changing relaxation modulus of the flakes as a function…
Advisors/Committee Members: Kamke, Frederick A. (committeechair), Loferski, Joseph R. (committee member), Watson, Layne T. (committee member), Dolan, James Daniel (committee member), Frazier, Charles E. (committee member), Lang, Elemer M. (committee member).
Subjects/Keywords: heat and mass transfer of porous solids; wood-based composites; hot-compression; process modeling; Monte Carlo simulation
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APA (6th Edition):
Zombori, B. G. (2001). Modeling the Transient Effects during the Hot-Pressing of Wood-Based Composites. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/27299
Chicago Manual of Style (16th Edition):
Zombori, Balazs Gergely. “Modeling the Transient Effects during the Hot-Pressing of Wood-Based Composites.” 2001. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/27299.
MLA Handbook (7th Edition):
Zombori, Balazs Gergely. “Modeling the Transient Effects during the Hot-Pressing of Wood-Based Composites.” 2001. Web. 11 Apr 2021.
Vancouver:
Zombori BG. Modeling the Transient Effects during the Hot-Pressing of Wood-Based Composites. [Internet] [Doctoral dissertation]. Virginia Tech; 2001. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/27299.
Council of Science Editors:
Zombori BG. Modeling the Transient Effects during the Hot-Pressing of Wood-Based Composites. [Doctoral Dissertation]. Virginia Tech; 2001. Available from: http://hdl.handle.net/10919/27299
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
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APA ·
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MLA ·
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CSE |
Export
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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.
Lenth, Christopher Allen.
Wood Material Behavior in Severe Environments.
Degree: PhD, Wood Science and Forest Products, 1999, Virginia Tech
URL: http://hdl.handle.net/10919/28826
► An improved knowledge of wood material behavior in hot-pressing environments can provide the benefit of an increased understanding of material properties during the manufacture of…
(more)
▼ An improved knowledge of wood material behavior in hot-pressing environments can provide the benefit of an increased understanding of material properties during the manufacture of wood-based composites as well as insight into the development of new processes and products which manipulate the viscoelastic nature of wood. Two specific areas where additional knowledge is needed are: the high temperature equilibrium moisture content (EMC) behavior and the moisture dependent softening behavior.
EMC data was collected and desorption isotherms were generated for mature and juvenile wood of aspen, loblolly pine and yellow-poplar at 50 and 160°C. High temperature EMC behavior was found to be distinct from that at lower temperatures, and considerable differences between the isotherms for juvenile and mature wood were detected. Substantial thermal degradation was observed during desorption at 160 °C and found to be strongly influenced by relative humidity.
The thermal softening behavior of wood was evaluated using dielectric thermal analysis (DETA) at moisture levels from 0 to 20 percent. Coincident in situ relaxations of hemicellulose and amorphous cellulose in the range of 20 to 200 °C were observed and found to exhibit the characteristics of a secondary (glass) transition. The moisture dependence of this transition was characterized, and differences in the observed Tg were detected between juvenile and mature wood. Time-temperature superposition was also shown to be applicable to the wood-water system.
Advisors/Committee Members: Kamke, Frederick A. (committeechair), Watson, Layne T. (committee member), Loferski, Joseph R. (committee member), Dillard, David A. (committee member), Zink-Sharp, Audrey G. (committee member), Frazier, Charles E. (committee member).
Subjects/Keywords: high temperature; equilibrium moisture content; viscoelasticity; thermal softening
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Record Details
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Lenth, C. A. (1999). Wood Material Behavior in Severe Environments. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/28826
Chicago Manual of Style (16th Edition):
Lenth, Christopher Allen. “Wood Material Behavior in Severe Environments.” 1999. Doctoral Dissertation, Virginia Tech. Accessed April 11, 2021.
http://hdl.handle.net/10919/28826.
MLA Handbook (7th Edition):
Lenth, Christopher Allen. “Wood Material Behavior in Severe Environments.” 1999. Web. 11 Apr 2021.
Vancouver:
Lenth CA. Wood Material Behavior in Severe Environments. [Internet] [Doctoral dissertation]. Virginia Tech; 1999. [cited 2021 Apr 11].
Available from: http://hdl.handle.net/10919/28826.
Council of Science Editors:
Lenth CA. Wood Material Behavior in Severe Environments. [Doctoral Dissertation]. Virginia Tech; 1999. Available from: http://hdl.handle.net/10919/28826
. 
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