Surface Modification of Fibers and Nonwovens with Melt Additives

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dc.contributor.advisor Dr. Alan Tonelli, Committee Member en_US
dc.contributor.advisor Dr.Behnam Pourdeyhimi, Committee Chair en_US
dc.contributor.advisor Dr.Eunkyoung Shim, Committee Co-Chair en_US
dc.contributor.advisor Dr. Keith Beck, Committee Member en_US
dc.contributor.advisor Dr. Jan Genzer, Committee Member en_US Datla, Vasantha Madhuri en_US 2010-04-02T19:01:55Z 2010-04-02T19:01:55Z 2008-12-19 en_US
dc.identifier.other etd-11292007-152318 en_US
dc.description.abstract 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 structural and geometrical differences between the films and fabrics clearly affected the polymer surface characteristics and migration on surface wettability. It is shown that hydroentangling and heat calendering, which are typical spunbond nonwoven bonding processes, resulted in changes in the fiber surfaces. Heat calendering hastened the blooming of the melt additive by facilitating surface migration leading to enhanced wettability over time and found that 130°C is an optimum temperature to bring the desired surface hydrophilicity (complete wettability) in PP films or fabrics with 2-wt% of ethoxylated alcohol melt additives. en_US
dc.rights I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dis sertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. en_US
dc.subject Surface modification en_US
dc.subject Wettability en_US
dc.subject Surface segregation en_US
dc.subject Polymer blend en_US
dc.subject Melt additives en_US
dc.title Surface Modification of Fibers and Nonwovens with Melt Additives en_US PhD en_US dissertation en_US Fiber and Polymer Science en_US

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