Polyester fiber physical properties

The physical properties of these fibers are compared with those of natural fibers and other synthetic fibers in Table 1. Additional property data may be found in compilations of the properties of natural and synthetic fibers (1). Apart from the polyolefins, acryhcs and nylon fibers are the lightest weight fibers on the market. Modacryhcs are considerably more dense than acryhcs, with a density about the same as wool and polyester. 

Standard polyester fibers contain no reactive dye sites. PET fibers are typically dyed by diffusiag dispersed dyestuffs iato the amorphous regions ia the fibers. Copolyesters from a variety of copolymeri2able glycol or diacid comonomers open the fiber stmcture to achieve deep dyeabiHty (7,28—30). This approach is useful when the attendant effects on the copolyester thermal or physical properties are not of concern (31,32). The addition of anionic sites to polyester usiag sodium dimethyl 5-sulfoisophthalate [3965-55-7] has been practiced to make fibers receptive to cationic dyes (33). Yams and fabrics made from mixtures of disperse and cationicaHy dyeable PET show a visual range from subde heather tones to striking contrasts (see Dyes, application and evaluation). 

Amino resins react with ceUulosic fibers and change their physical properties. They do not react with synthetic fibers, such as nylon, polyester, or acryhcs, but may self-condense on the surface. This results in a change in the stiffness or resiHency of the fiber. Partially polymerized amino resins of such molecular size that prevents them from penetrating the amorphous portion of ceUulose also tend to increase the stiffness or resiHency of ceUulose fibers. 

Some of the common types of plastics that ate used ate thermoplastics, such as poly(phenylene sulfide) (PPS) (see Polymers containing sulfur), nylons, Hquid crystal polymer (LCP), the polyesters (qv) such as polyesters that ate 30% glass-fiber reinforced, and poly(ethylene terephthalate) (PET), and polyetherimide (PEI) and thermosets such as diaHyl phthalate and phenoHc resins (qv). Because of the wide variety of manufacturing processes and usage requirements, these materials ate available in several variations which have a range of physical properties. 

Table 3. Physical properties and chemical resistance of polyester fibers.

TABLE 2.12 Physical Properties of Poly(ethylene terephthalate) (PET) and Polyethylene 2,6-naphthalate) (PEN) Polyester Fibers... 

Since unsaturated polyester resins alone would have insufficient strength for structural application, reinforcements are used to enhance the physical strength of such resins. Typically, tensile strength, impact strength and stiffness are the physical properties of most interest. Reinforcements can be regular particulates, as in glass microspheres, irregular particulates, as in flakes, or fibers. 

The DuPont research team turned from the synthesis of polyesters to tackle, more successfully, the synthesis of the first synthetic fiber material, nylon, which approached, and in some cases exceeded, the physical properties of natural analogs (Section 4.7). The initial experience with polyesters was put to good use in the nylon venture. 

The resin matrix can be either thermosetting or thermoplastic. Thermosetting resins such as epoxy, polyimide, polyester, and phenolic are used in applications where physical properties are important. Polyester and epoxy composites make up the bulk of the thermoset composite market. Of these two, polyesters dominate by far. Reinforced with glass fiber, these are known as fiberglass-reinforced plastics (FRPs). FRPs are molded by layup and spray-up methods or by compression molding either a preform or sheet molding compound (SMC). 

Summaries of chemical and physical properties of different polyester fibers are available (107). Polyesters display excellent resistance to conventional textile bleaching agents and are most resistant to cleaning solvents (107). Mold, mildew, and fungi may grow on finishes applied to polyester fabrics but do not attack the fiber itself (3). Again, insects that devour natural fibers normally do not affect polyester fibers although they may cut their way out of the fabric if trapped. 

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. 

Our study is outlined in five parts, (a) Two polystyrene plastics were reinforced at different fiber contents alternately with polyester, asbestos, and glass fibers, (b) The mechanical/physical properties of the resultant monofiber-reinforced plastics were determined and compared, (c) Combinations of fibers were then used to fabricate multifiber-rein-forced structures to exploit simultaneously the particular advantages of the different reinforcements, (d) The effect of each fabrication stage on the molecular weight and molecular weight distribution of the matrix plastics was established and (e) a linear mathematical model was formulated to predict the properties of multifiber structures and forecasted values compared with corresponding values experimentally obtained from (c) above. 

Table I. Mechanical/Physical Properties of Polyester Fiber-Reinforced Polystyrene0...

Typical condensation polymers, such as polyester and nylon, often exhibit these properties. If the fiber is to be ironed, its Tg should be above 200 °C if it is to be drawn from the melt, its Tg should be below 300 °C. Branching and cross-linking are undesirable because they disrupt crystalline formation even though a small amount of cross-linking may increase some physical properties if effected after the material is suitably drawn and processed. 

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