Abstract

Abstract 1. The treatments of relaxation phenomena in polymer systems, due to Kuhn, and Alexandrov and Lazurkin, are outlined and discussed. 2. Eyring's rate equation is used to analyze the rates of orientation of long-chain molecules in a stressed specimen of lightly vulcanized rubber. The data are compared with similar data on viscous flow in raw rubber, and it is suggested that the segment size for movement is the same in both cases. In viscous flow, the segmental movement occurs without appreciable internal rotation within the segment. In elastic orientation, however, it appears that a high degree of internal rotation within the segment accompanies the formation of the activated state. 3. The activation energy for the orientation of long chains is separated into two terms: (1) the energy required to free a segment from its neighbors, (2) the energy of activation for rotation around C—C bonds. It is suggested that the main effect of vulcanization and plasticizers is on term (3); vulcanization tends to increase this term, plasticizers to decrease it. 4. Data on the dielectric dispersion of polyvinyl chloride suggests the need for internal rotational activation in this case, as in orientation elasticity. This is in agreement with what we should qualitatively expect. Possible complications due to crystallinity in rubber at high extensions or low temperatures are briefly discussed.

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