Polyester fibers, modified, surface

Surface Analysis of Modified Polyester Fibers Utilizing a Variety of Spectroscopic Methods. 

Control of fiber friction is essential to the processing of fibers, and it is sometimes desirable to modify fiber surfaces for particular end-uses. Most fiber friction modifications are accomplished by coating the fibers with lubricants or finishes. In most cases, these are temporary treatments that are removed in final processing steps before sale of the finished good. In some cases, a more permanent treatment is desired, and chemical reactions are performed to attach different species to the fiber surface, e.g. siliconized slick finishes or rubber adhesion promoters. Polyester s lack of chemical bonding sites can be modified by surface treatments that generate free radicals, such as with corrosive chemicals (e.g. acrylic acid) or by ionic bombardment with plasma treatments. The broken molecular bonds produce more polar sites, thus providing increased surface wettability and reactivity. 

The surface of the synthetic polymers can be modified by chemical, physical, and enzymatic methods (Figure 4.1). Chemical modification requires harsh reaction due to which strength properties of polymers get affected. Zeronian and Collins (1989) reported a 10-30% weight loss in polyester fibers after chemical treatment. Additionally, chemical treatments are difficult to control and have negative impacts on the enviromnent. 

Pripol. [Unichema Unichema France SA] IMmer or trimer acids modifier for nylon, polyester fibers used in polyamide for hot melt adhesives, thermographic inks, urrfhane elastomers, industrial lubricants, fuel additives, surface coadng resins, spin finishes. 

Synthetic fibers do not contain natural impurities although there are added impurities such as sizing materials and oil stains. Therefore, their pretreatment process is simpler than other natural fibers. However, synthetic fibers such as polyester and acrylic have poor wettability, dyeability, and antistatic behavior. After plasma treatment, the fiber surface gets physically altered, and hydrophilic functional groups are introduced to the fiber surface, which improves the wettability of the fiber significantly. In recent years, many researchers have studied ways to modify polyester textile materials, and good results have been obtained (Morent et al., 2008). 

A. Ghenaim, A. Elachari, M. Louati, C. Gaze, Surface energy analysis of polyester fibers modified by graft fluor-ination. Journal of Applied Polymer Science 75 (2000) 10. 

Zini et al. [50] prepared composites of a bacterial copolyester poly(3-hydroxybutyrate-co-3-hydroxyhexanoate], P(3HB-co-3HH), reinforced with flax fibers by compression molding. In order to improve fiber-matrix adhesion in composites, fibers chemically modified at the surface (by acetylation or by short-chain-PEG grafting] were also used. The best results were obtained with surface acetylated fibers. In the flax fiber composites the crystallization rate of P(3HB-co-3HH] remarkably increased compared with that of the plain polyester. The fibers displayed a nucleating effect on P(3HB-co-3HH] crystallization, whose magnitude depended on fiber surface chemistry. This feature was confirmed by the appearance of trans-crystallinity in isothermal crystallization experiments run in a hot stage of a polarized optical microscope. 

The white cell adsorption filter layer is typically of a nonwoven fiber design. The biomaterials of the fiber media are surface modified to obtain an optimal avidity and selectivity for the different blood cells. Materials used include polyesters, eg, poly(ethylene terephthalate) and poly(butylene terephthalate), cellulose acetate, methacrylate, polyamides, and polyacrylonitrile. Filter materials are not cell specific and do not provide for specific filtration of lymphocytes out of the blood product rather than all leukocytes. 

Coatings and Surface Modifications. Probably the one application of photopolymer chemistry that has the most worldwide commercial value in terms of product sales is the use of photopolymer materials for curable coatings. Most of the wood paneling and less expensive furniture manufactured today utilize UV or electron-beam curable materials for decorative finishes (e.g. simulation of wood grain) and protective coatings. In addition, the surfaces of many commercially important materials (e.g. textile fibers and polyester films) are being modified by photopolymer processes. 

The core-sheath (c-s) configuration is adaptable because many different polymers may be applied as a sheath over a solid polyester core, thus giving a variety of modified surface properties while maintaining all the major fiber and textile properties of PET. An early patent by Shima and coworkers uses an eccentric core-sheath configuration to achieve spiral crimp in a yarn [67]. A recent patent by Chang and coworkers discloses the use of side-side or eccentric c-s bicomponent fibers to achieve a self-crimping yarn made from polytrimethylene terephthalate, where one component is a melt-blend of PTT with a small amount of polystyrene [68]. 

Furthermore, Abral et at [49] studied the characteristics of water hyacinth fiber and its composite with unsaturated polyester. An alkali treatment was used to modify the surface of the WHF. The WHF was treated in various alkali concentrations for 1 h... 

For the preparation of polymer composites, xmsaturated polyester resin was reinforced with raw and surface-modified particle (90 microns) fibers in four different proportions... 

Figure 13.1 Tensile strength of different surface-modified Grewia optiva particle fibers-reinforced unsaturated polyester composites.

Water absorption results of neat UPE and its composites reinforced with raw, mercerized and benzoylated fibers have been shown in Table 13.1. It can be seen from the table that water absorption characteristics of polymer composites depend upon the content of fiber loadings, water immersion time and surface modification techniques. The water absorption of raw and surface-modified fiber-reinforced UPE composites has been found to increase with the increase in percent loading. Similar results were also reported by Rashdi et ah during their studies on the water absorption behavior of kenaf fibers-reinforced polyester composites [27]. This may be due to greater affinity of water for OH groups present on the fiber backbone, whose number increases with the increase in fiber contents. In comparison to raw filler, composites reinforced with surface-modified filler exhibited low water absorption, which may be due to the reduction in the hydrophilic character of cellulosic biofibers after surface modification. 

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