Effects of Molecular Weight and Molecular Weight Distribution on the Physical Properties of Cis-Polyisoprenes.

摘要

Stress relaxation and shear creep measurements were made on a series of fourteen cis-polyisoprenes of known molecular weight and molecular weight distribution. The objective was to test an earlier empirical relationship developed by Tobolsky for describing the relaxation behavior in the rubbery plateau and flow regions. It was found that for those samples that did not crystallize, a correlation could be made between the molecular weight variables and the empirical constants in the Tobolsky relationship. The major molecular parameter was found to be the influence of molecular weight on the degree of molecular entanglements. It was noted that the molecular weight between entanglements increases directly with the log Mw.