Fibers stretched, retractive forces

Retractive forces in animal fibers stretched into the Hookean region of the stress-strain curve are generally attributed to the stretching of chemical bonds and hence to an increase in the internal energy of the fiber (Ast-bury and Haggith, 1953 Peters, 1956). 

Miscibility or compatibility provided by the compatibilizer or TLCP itself can affect the dimensional stability of in situ composites. The feature of ultra-high modulus and low viscosity melt of a nematic liquid crystalline polymer is suitable to induce greater dimensional stability in the composites. For drawn amorphous polymers, if the formed articles are exposed to sufficiently high temperatures, the extended chains are retracted by the entropic driving force of the stretched backbone, similar to the contraction of the stretched rubber network [61,62]. The presence of filler in the extruded articles significantly reduces the total extent of recoil. This can be attributed to the orientation of the fibers in the direction of drawing, which may act as a constraint for a certain amount of polymeric material surrounding them. 

Earlier attempts to use the AFM for mechanically stretching chromatin fibers have run into a rather unexpected artifact. Long native chromatin fibers isolated from chicken erythrocytes, or fibers assembled in vitro from purified histones and relatively short, tandemly repeated DNA sequences were deposited on mica or glass surfaces and pulled with the AFM tip [69,70]. In such stretching experiments the scanning of the sample in the x- and y-direction used for imaging was disabled, and the cantilever-mounted tip was allowed to move only in the z-direction, i.e., upwards and downwards, away and towards the surface. When the AFM tip is pushed into the sample, it may attach to the sample by non-specific adsorption upon retraction it stretches the sample and force-extension curves are recorded (see Fig. lb for an explanation of a typical force curve). 

Optim max utilizes a key benefit of the manufacturing process that allows the extent of set in the fiber to be manipulated in a controlled manner. Optim max fiber is wool that has been temporarily set while stretched, so that the fiber retracts when released in hot moist conditions by about 25% in length. This fiber offers scope for innovation in yarn and fabric design. For example, when Optim max is blended with normal wool, spun into yam, and relaxed in hank form in hot water, the Optim max fibers retract and force the normal wool fibers to buckle. 

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