Hard elastic fibers. II. Destructible and indestructible microparacrystals and their importance for understanding the properties of hard elastic fibers

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Abstract
A new structural model is introduced for hard elastic fibers based on nuclear magnetic resonance measurements and supplemented by known facts about the structure of nonelastic meltcrystallized polymers, electron micrographs of 300 A thick hard elastic films, and carlorimetric deformation results. The microparacrystals (mPC's) build up perfectly regular lamellae, the distances between which increase uniformly during straining. This is explained by a three-dimensional network which is relatively weak compared with the stiffness of the lamellae. Only the mPC's at the lamellar ends can be destroyed under stress (dmPC's). Their large free surface produces the reverse driving forces. Exothermal effects during straining can be partially explained by the heat of gas adsorption at these newly generated free surfaces. The destructible mPC's are the elastic tie-points between adjacent lamellae and correspond to the taut connection between leaf springs and the oriented chains in the models of Noether et al. and Gdritz and Müller.