Modified PES Fibers

Since disperse dyes diffuse very slowly into PES fibers, efforts have been made to increase the rate of dye strike by chemical or physical alteration of the fiber. The fiber is also modified to reduce the pilling tendency, to increase shrinkage and elasticity, and to reduce flammability. Such modified fibers exhibit improved dye receptivity. Fibers with improved dyeability can be dyed with disperse dyes at boiling temperature without a carrier or with basic dyes when they are modified with acidic components (5-sulfoisophthalic acid). Fibers of this type are used if dyeing cannot be carried out easily above 100°C (e.g., in the case of floor coverings, articles made of PES-wool blends, stretch materials, and cord). Strongly crimped PES bicomponent fibers are produced for special purposes. These fibers are normally also dyeable at the boil and without a carrier [136, 137, 138], 

Modified PES fibers are usually more sensitive to hydrolysis than normal fibers. The lightfastness of the dyeings is often lower than on normal fibers. Thus, dyes for coloring carpeting, upholstery, and drapery must be carefully selected. On modified PES fibers dyes start exhausting at low temperatures (ca. 60°C) and the dyebath is exhausted after a short time, so problems with levelness may arise. 

The joint use of anionically modified and normal PES types can be exploited for differential dye effects (joint application of different classes of dyes that differ in their affinity to the fiber components). 

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Elastomeric polyurethane fibers [96, pp. 609-615], are contained in stretch articles and in knitted fashion materials. Light shades can be dyed tone-on-tone on polyamide-polyurethane mixtures with disperse dyes at 95-98°C and pH 6-7. However, the wetfastness of these dyeings on polyurethanes is lower than on polyamide. Because of the temperature sensitivity of polyurethane fibers, mixtures of elastomeric and polyester fibers must be dyed with small-molecular, rapidly diffusing disperse dyes in 30 min at 120 °C according to the HT process [148], Modified PES fibers that are dyeable at 100°C without a carrier are often used in mixtures with elastomeric fibers. In all dyeing processes for elastomeric fibers, dyeing equipment that permits low-strain guidance of the material and the lowest possible thermal stress are important. 

More recently, the same research group also reported that in hydro-calcite nanoparticle modified PE fibers [21] the incorporation of clay improved the thermal stability and induced heterogeneous nucleation of polyethylene crystals. Hydrocalcite exhibited good dispersion into the polymer matrix, and hence positively affected the mechanical properties in terms of both stiffness and strength. The toughness of the nanocomposite as spun fibers was also increased up to 30% with respect to neat polymer. 

Post-Treatment of Hollow Fibers. End use of ihe hollow-fiber membrane dictates the ty pe of post-tre.iiment. if any There are three main categories fibers thal are spun, fibers that vv ill be chemically or physically modified, and fibers that will serve as a porous matrix lor support ol another lactivc) polymer deposited (nr entrapped) upon (or within) its walls. There is no theoretical impediment to the inclusion of all conventional treatments in the spinning line photochemical cross-linking, llmirinniion, and anliplaslici/ers have been successful. 

Gel-spinning is a method of "modifying PE which, as Figure 12 shows, produces fibers with exceptional properties and which can produce a wide variety of strength-to-stiffness combinations [3]. 

Fig. 12. Stress-strain dependence for corona modified composites. Fiber volume fraction 28%. C/PE - no treatment, C/TPE - fiber only treated, TC/PE - PE only treated, TC/TPE - fiber and PE both treated. (After ref 65).

Penn, L.S., Tesoro, G.C. and Zhou, H.X., Some effects of surface-controlled reactions of Kevlar 29 on the interface in epoxy composites. Polym. Compos., 9, 184-191 (1988). Ozzello, A., Grummon, D.S., Drzal, L.T., Kalantar, J., Loh, I.-H. and Moody, R.A., Interfacial shear strength of ion beam modified LTHMW-PE fibers in epoxy matrix composites. Proc. Mater. Res. Soc. Symp., 153, 217-222 (1989). 

Polymers of MMA, AAc, and MAA were grafted onto an ultrahigh molecular weight polyethylene (UHMWPE) fiber surface after pretreatment with electron beam irradiation [31]. Sundell et al. [32] pretreated a PE film with electron beams to facilitate the graft polymerization of vinyl benzylchloride onto the substrate. The inner surface of porous PE hollow fiber had also been modified by grafting of glycidyl methacrylate (GMA) polymer after electron beam irradiation [33]. 

Uses Reducing agent in redox-catalyzed polymerization color stabilizer, modifier, catalyst for polyamides antioxidant intermediate for forming metallic salts used as stabilizers accelerator for org. peroxide catalysts improver of polysiloxane resins free radical promoter in emulsion polymerization promoter in polyester resin curing mfg. of self-extinguishing fibers (reacts with polyester resin and polyolefin) color/odor inhibitor, catalyst for some thermoplastics discoloration inhibitor in PE corrosion inhibitor on thin aluminum surfs. lubricity improver in polyphenyl thioether-based lubricants Manuf./Distrib. Akzo Nobel http //www.akzonobel.com, Ferro http //WWW. ferro. com... 

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