Biconstituents

Other elastomeric-type fibers iaclude the biconstituents, which usually combine a polyamide or polyester with a segmented polyurethane-based fiber. These two constituents ate melt-extmded simultaneously through the same spinneret hole and may be arranged either side by side or ia an eccentric sheath—cote configuration. As these fibers ate drawn, a differential shrinkage of the two components develops to produce a hehcal fiber configuration with elastic properties. An appHed tensile force pulls out the helix and is resisted by the elastomeric component. Kanebo Ltd. has iatroduced a nylon—spandex sheath—cote biconstituent fiber for hosiery with the trade name Sidetia (6). 

Fig. 1. Stress—strain curves A, hard fiber, eg, nylon B, biconstituent nylon—spandex fiber C, mechanical stretch nylon D, spandex fiber E, extruded latex...

More recentiy, melt-spun biconstituent sheath—core elastic fibers have been commercialized. They normally consist of a hard fiber sheath (polyamide or polyester) along with a segmented polyurethane core polymer (11,12). Kanebo Ltd. in Japan currentiy produces a biconstituent fiber for hosiery end uses called Sideria. 

Nylon—spandex sheath—core biconstituent fiber. 

Fig. 2. Ultrafine fibers are produced by spinning bicomponent or biconstituent polymer mixtures, highly stretching such products to ultrafine deniers, and extracting or otherwise removing the undesked matrix carrier to release the desked ultrafine fibers (30). For example, spinning polyester islands in a matrix of polystyrene and then, after stretching, dissolving the polystyrene to leave the polyester fibers cospinning polyester with polyamides, then stretching,...

M.W. Olson G.H- Brice, Bicomponent and Biconstituent Fibers in Ballistic Fabric for Personnel Armor , Rept No USA-NLabs, C/-PLSEL-TR-71-48CE, TS-173, Contract DAA17-70-C-0032, Uniroyal Inc, Wayne (1971)... 

Biconstituent fibres eonsisting fibrils of a polymer aligned parallel to the fibre length interspersed in a continuous matrix of another polymer and their structure, resembles the bilateral strueture of wool. Clearly fibrillar-matrix ratio and the nature and relative dimension of the eomponents can be altered to vary the physico-... 

Fiber biconstituent A hybrid or composite fiber comprising a dispersion of fibrils of one synthetic plastic within and parallel to the longitudinal axis of another also a construction of plastic and metal or alloy filaments. 

Blends of two fiber-forming polymers can be used to spin several types of two-component fibers (Allied Chemical Corp., n.d. Buckley and Phillips, 1969 Cresentini, 1971 Fukuma, 1971 Hayes, 1969 Mumford and Nevin, 1967 Papero et ai, 1967 Pollack, 1971). As shown in Figure 9.3, the two components may be arranged as mated half-cylinders, in a skin-core configuration, or in a matrix-fibril configuration. The first two configurations are referred to as bicomponent, the last as biconstituent fibers. 

Figure 9.3. Classification of bicomponent and biconstituent fibers. (Allied Chemical Corp., advertising literature) (A) Bicomponent system (B) skin-core system (C) matrix-fibril system.

Figure 9.5. Micrograph of a drawn biconstituent fiber containing 30 % poly(ethylene terephtha-late) and 70 % nylon 6. The fibers form elongated, tapered cylinders about 100-200 //m in length. (Buckley and Phillips, 1969.)...

A second important type of biconstituent fiber is a semicompatible blend on nylon 66 with nylon 61 (I referring to isophthalic acid), with nylon 61... 

The crystalline bicomponent and biconstituent blends considered above may also be compared to the polyallomer block copolymers (Section 6.8), which consist of two crystalline components linked together by chemical bonds rather than by mechanical mixing. In all cases, the constituents are independently crystallizable. Melt-blending theory is considered in Section 9.6. 

Figure 9.7. Differential thermal analysis of nylon 6, polyethylene terephthalate (PET), and some biconstituent compositions (a) PET (b) 45% PET/55% nylon (c) 30% PET/70% nylon (d) 10 % PET/90 % nylon (e) nylon. (Buckley and Phillips, 1969.)...

The mechanical behavior of isomorphic macromolecular systems would be expected to be quite different from the behavior observed in bicomponent or biconstituent systems. Indeed, isomorphic systems would be expected to behave in many respects like crystalline homopolymers, except that such properties as 7 and lattice spacings may be dependent on composition. Because of the single-phase situation, the glass-rubber transition and related properties may be expected to behave as if a random copolymer... 

The biconstituent and bicomponent polymer pairs, discussed in Section 9.2. 

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