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You searched for +publisher:"North Carolina State University" +contributor:("Dr. Alan Tonelli, Committee Member"). Showing records 1 – 2 of 2 total matches.

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North Carolina State University

1. Gupta, Amit. Novel Approaches to Fiber formation from Hydrogen Bond forming Polymers.

Degree: PhD, Fiber and Polymer Science, 2009, North Carolina State University

Hydrogen bond forming polymers such as aliphatic polyamides and polyvinyl alcohol are important engineering plastics with good mechanical properties, high melting point and good chemical resistance. However, any further attempt at improving their mechanical properties gets thwarted due to the presence of intermolecular hydrogen bonding. Many approaches have been attempted in the past to suppress hydrogen bonding in aliphatic polyamides and have met with little or no success. These include, plasticizing the structure, dry spinning, wet spinning, gel spinning, and zone drawing/annealing. We have employed a new technique that involves the dry-jet wet spinning and drawing of GaCl3/nylon 66 complex. This new method allows traditional low draw ratios for nylon 66 to be increased by disrupting the interchain hydrogen bonded network. Fibers with a high modulus were obtained when high molecular weight nylon 66 was used. Further, we have also reviewed the concept of thermoreversible gelation and its application for gel spinning of ultra high molecular weight polyethylene fibers. We developed high strength and modulus nylon 6 and PVA fibers from the gels of these polymers in N-methyl pyrrolidinone. High molecular weight is essential for achieving more drawing of polymer chains which leads to high molecular orientation. Electrostatic spinning or electrospinning has received considerable research attention in recent years. It involves the application of an electric filed to a polymer solution or melt to facilitate production of fibers in the sub-micron down to nanometer range. We have investigated the complexation of GaCl3 with nylon 6 and developed porous nanofibers via the technique of electrospinning. Pores are generated by removal of salt from the as spun nanofibers via dipping in water. Researchers have tried in the past using a highly volatile solvent, or selective removal of one polymer from a bicomponent nanofiber for developing pores in nanofibers. However, using a metal salt proved to be a simple and fast approach for generating pores in electrospun nanofibers. Advisors/Committee Members: Dr. Samuel Hudson, Committee Member (advisor), Dr. Alan Tonelli, Committee Member (advisor), Dr. Saad Khan, Committee Co-Chair (advisor), Dr. Richard Kotek, Committee Chair (advisor).

Subjects/Keywords: Hydrogen Bonding; Gel Spinning; Nanofibers

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Gupta, A. (2009). Novel Approaches to Fiber formation from Hydrogen Bond forming Polymers. (Doctoral Dissertation). North Carolina State University. Retrieved from http://www.lib.ncsu.edu/resolver/1840.16/4526

Chicago Manual of Style (16th Edition):

Gupta, Amit. “Novel Approaches to Fiber formation from Hydrogen Bond forming Polymers.” 2009. Doctoral Dissertation, North Carolina State University. Accessed May 09, 2021. http://www.lib.ncsu.edu/resolver/1840.16/4526.

MLA Handbook (7th Edition):

Gupta, Amit. “Novel Approaches to Fiber formation from Hydrogen Bond forming Polymers.” 2009. Web. 09 May 2021.

Vancouver:

Gupta A. Novel Approaches to Fiber formation from Hydrogen Bond forming Polymers. [Internet] [Doctoral dissertation]. North Carolina State University; 2009. [cited 2021 May 09]. Available from: http://www.lib.ncsu.edu/resolver/1840.16/4526.

Council of Science Editors:

Gupta A. Novel Approaches to Fiber formation from Hydrogen Bond forming Polymers. [Doctoral Dissertation]. North Carolina State University; 2009. Available from: http://www.lib.ncsu.edu/resolver/1840.16/4526

2. Datla, Vasantha Madhuri. Surface Modification of Fibers and Nonwovens with Melt Additives.

Degree: PhD, Fiber and Polymer Science, 2008, North Carolina State University

Polypropylene (PP) fibers, widely utilized in woven and nonwoven industry, have highly inert and hydrophobic surfaces. Therefore a modification aimed at the creation of a more polar surface is an important issue in the application areas where wettability and adhesion properties are required. One way to impart surface hydrophilicity into polypropylene is blending of the melt additives prior to or during the fiber spinning process. It is reported that some oligomeric melt additives spun with host polymer migrate to surface and generate surface reactivity at low concentration without altering bulk properties. The principal objective of the study is to explore effective ways of imparting hydrophilicity to polypropylene fibers and nonwovens with the melt additives based on an understanding of hydrophilic surface formation on polypropylene and key parameters related to the process. It involves study of possible interactions between polypropylene polymer and the melt additive leading to a hydrophilic surface by melt additive surface migration. For this purpose, different classes of nonionic melt additives were melt extruded with a twin-screw extruder using a melt additive concentration of 2% to investigate how hydrophilic surfaces are created. The mechanism of hydrophilic surface creation by melt additives was explored using X-ray photoelectron spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), Atomic Force Microscopy (AFM) and dynamic contact angle analyses. XPS analysis revealed migration and surface enrichment of melt additives by increase in the surface amount of polar oxygen groups leading to a more hydrophilic surface. Melt additives with different chemistries were studied for their surface modifying effectiveness. It is found that both size and characteristics of hydrophilic and hydrophobic groups in melt additives as well as their relative size; represented by HLB (Hydrophilic-Lipophilic Balance) value, affect the rate and the degree of surface additive segregation. The surface energy and the polar contribution of the polypropylene film increased due to the migration of low-molecular-mass components (additives) to the surface resulting in increase in surface wettability. Low molecular weight oxidized materials were observed in the form of a globular morphology on the surface of the film. Additionally thermal analysis of melt blended PP films using DSC revealed phase-separated nature. We also found that resulting surface characteristics are very dynamic, so melt additive containing polymer surfaces response to water or heat application effected surface properties and composition. Some melt additive containing PP films response to water enhanced surface migration and wettability leading to a durable hydrophilic PP surface. Analyses of melt additive concentration effects established that the minimum additive concentration to cause surface chemical changes is about 1 wt%. Finally evaluation of surface properties of spunbond PP nonwoven fabrics with the melt additives indicated that the… Advisors/Committee Members: Dr. Alan Tonelli, Committee Member (advisor), Dr.Behnam Pourdeyhimi, Committee Chair (advisor), Dr.Eunkyoung Shim, Committee Co-Chair (advisor), Dr. Keith Beck, Committee Member (advisor), Dr. Jan Genzer, Committee Member (advisor).

Subjects/Keywords: Surface modification; Wettability; Surface segregation; Polymer blend; Melt additives

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Datla, V. M. (2008). Surface Modification of Fibers and Nonwovens with Melt Additives. (Doctoral Dissertation). North Carolina State University. Retrieved from http://www.lib.ncsu.edu/resolver/1840.16/4838

Chicago Manual of Style (16th Edition):

Datla, Vasantha Madhuri. “Surface Modification of Fibers and Nonwovens with Melt Additives.” 2008. Doctoral Dissertation, North Carolina State University. Accessed May 09, 2021. http://www.lib.ncsu.edu/resolver/1840.16/4838.

MLA Handbook (7th Edition):

Datla, Vasantha Madhuri. “Surface Modification of Fibers and Nonwovens with Melt Additives.” 2008. Web. 09 May 2021.

Vancouver:

Datla VM. Surface Modification of Fibers and Nonwovens with Melt Additives. [Internet] [Doctoral dissertation]. North Carolina State University; 2008. [cited 2021 May 09]. Available from: http://www.lib.ncsu.edu/resolver/1840.16/4838.

Council of Science Editors:

Datla VM. Surface Modification of Fibers and Nonwovens with Melt Additives. [Doctoral Dissertation]. North Carolina State University; 2008. Available from: http://www.lib.ncsu.edu/resolver/1840.16/4838

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