Relative draw ratio effect

Figure 6.8 Schematic illustration of the effect on the draw ratio of the relative rates of elongation and chain slippage, (a) Initial state (b) slippage rate elongation rate (c) elongation rate slippage rate (d) slippage rate optimum for elongation rate. (Singh, H., and R MacRitchie. 2001. Journal of Cereal Science 33231-243.)...

Jump-like creep was also studied for UHMWPE films with intentionally varied structural organization of interfaces between fibrils at the expense of their different preparation (gel-casting, crystallization from the melt), various draw ratios X (from 7 to 119), and the special cross-linking of fibrils [315,317]. The fibrils were weakly connected and loosely packed, weakly tied but closely packed, or cross-linked by long molecular segments or connected by short crosslinks, in these samples. As a result, absolutely different jump-like creep rate vs deformation curves and jump sharpness parameter h vs strain dependencies were obtained for these model samples with different interfacial structures. Short interfibrillar crosslinks provided the largest effect on creep behavior. Creep occurred basically through shear of fibrillar structural units relative to one another in an acceleration-deceleration way deceleration was due to slip resistance by some stoppers. ... 

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Tensile drawing of the wet polyacetylene films yielded a maximum stretching ratio of about 15 for the thick films and about 10 for thin films. By contrast, fully dried polyacetylene films could not be extended beyond 6 times their original length under otherwise similar experimental conditions. Some variation in the maximum stretching ratio, Xmax. was found, dependent on the characteristics of the liquid used as "plasticizer . Specifically, it was observed that Xmax was dependent on the boiling point and the specific composition in the case of mixed liquids. The results seem to indicate that Xmax is dependent on the relative content of solvent in the film and on the speed of evaporation of the solvent from bulk of the film. Hexadienes, for example, were found to be excellent plasticizers for polyacetylene, presumably due to the easier penetration of these liquids into the polyacetylene lattice because of the similarity in molecular structures. Pure aromatic solvents appeared to be the least effective however, a 4 1 mixture of toluene and cumene yielded excellent results. 

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