Bicomponent and Biconstituent Fibers

Poly butadiene having a high content of cis 1,4 groups is difficult to process and also has a low coefficient of friction. Blending with an oil-extended styrene-butadiene rubber (SBR) overcomes these disadvantages, without adversely affecting resilience or chemical stability. 

The blending of natural rubber with SBR imparts increased resilience and tack. Increased resilience arises because of the ability of natural rubber to crystallize on deformation. 

The field of rubber-rubber blends was recently reviewed by Cornish and Powell (1974), who pointed out that the continuous phase in the blend usually has the higher concentration of polymer or the lower viscosity or both (see Section 9.6). 

Strictly speaking, the bicomponent systems are not polyblends in the classic sense, since the dimensions along the fiber axis have macroscopic 

One interesting, simple bicomponent fiber is made from two types of nylon. If the polymers are selected to have different coefficients of expansion, the resultant fiber will curl or crimp on cooling. This characteristic imparts bulk and stretchiness to the yarn made from the fibers. 

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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)... 

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.

Common cross sections of man-made fibers include round, trilobal, pentalobal, dog-bone, and crescent shapes. Whai two polymers are used in fiber formation as in bicomponent or biconstituent fibers, the two components can be arranged in a matrix, side-by-side, or sheath-core configuration. Round cross sections are also found where skin formation has caused fiber contraction and puckering (as with rayons) has occurred or where the spinneret shape has provided a hollow fiber. Complex fiber cross-sectional shapes with special properties are also used. See Figure 1-5. 

On drawing and orientation the man-made fibers become smaller in diameter and more crystalline, and imperfections in the fiber morphology are improved somewhat. Side-by-side bicomponent or biconstituent fibers on drawing become wavy and bulky. 

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,...

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. 

Biconstituent fiber of nylon 6 with polyester microfibrils dispersed throughout the fiber matrix has been marketed under the trade name Source (Allied). The fiber is reported to have unique optical and dyeing properties and a higher strength and lower regain than nylon 6,6 and is used primarily in carpets. A sheath-core bicomponent fiber containing a nylon 6 sheath and a polyester core has been reported al so. It is said to have properties that are intermediate between both fibers. 

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