Analysis of the equations of state of polyolefin melts in terms of the simha‐somcynsky hole theory

Abstract

AbstractPressure–volume–temperature data on melts of low‐density polyethylene, polypropylene (PP), poly(butene‐1) (PBT), and poly(4‐methylpentene‐1) (PMP) previously reported by us have been evaluated in terms of the Simha–Somcynsky hole theory of polymeric liquids by a determination of the reducing parameters P*, V*, and T* for each system. Literature data on the reducing parameters of linear polyethylene and of a branched polyethylene of intermediate density are also considered. Agreement with theory is best for the polyethylenes and deteriorates markedly in the series PBT:PP:PMP. These higher polyolefins have very low values of P*, thus suggesting a deficiency of the Simha–Somcynsky theory at high reduced pressures P̃ = P/P*. In these polyolefins, systematic variations of the reducing parameters (and molecular parameters derived therefrom) are noted and discussed. Correlations found previously between T* and the moleculer weight M0 of the effective segment of the theory or its hard‐core volume M0V* are obeyed by the polyethylenes only. The higher polyolefins show serious deviations from these correlations.