Shrinkage fiber

Crimp. The tow is usually relaxed at this point. Relaxation is essential because it gready reduces the tendency for fibrillation and increases the dimensional stabiUty of the fiber. Relaxation also increases fiber elongation and improves dye diffusion rates. This relaxation can be done in-line on Superba equipment or in batches in an autoclave. Generally saturated steam is used because the moisture reduces the process temperatures required. Fiber shrinkage during relaxation ranges from 10 to 40% depending on the temperature used, the polymer composition used for the fiber, and the amount of prior orientation and relaxation. The amount of relaxation is also tailored to the intended apphcation of the fiber product. 

Dimensional Stability. Dimensional stabiHty refers to how a fiber changes length under the influence of load or heat. Conventionally described in terms of fiber shrinkage (ASTM D885-64) at a defined temperature, the term has also come to mean time dependent length change or creep. 

Handbuilder for most fibers, shrinkage control for cellu-losics, and crosslinker for polymers... 

Sakthivel [207] annealed commercially produced fiber and measured changes in crystal size and shrinkage of the fibers during annealing at different temperatures. Table 3.28 gives the crystal sizes and Table 3.29 gives the fiber shrinkage. 

Histopathological examination of scleroderma-like lesions showed distended collagen fibers, shrinkage of elastic fibers, interstitial edema, sometimes perivascular lymphocytic infiltrates, swollen endothelial cells of the enlarged capillaries, and marked acanthosis in the epidermal layer (Czernielewski et al. 1979). 

Before the acrylic fibers (qv) produced in the wet-spinning process can be subjected to the elevated temperatures of carbonization, they must be converted to a thermally stable form that will not melt through oxidative stabilization. Stabilization is usually performed in air at temperatures between 200 and 300°C (27) and under tension to prevent fiber shrinkage (28). 

Dimensional stability is another important physical property of textile fibers. Shrinkage describes the widthwise or lengthwise contraction of a fiber, yam, or fabric, usually after wetting and redrying or on exposure to elevated temperatures. 

The level of fiber shrinkage strongly affects the final paper properties. In general, there are two possible strategies of paper drying ... 

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