Diffusivities and solubilities of methane in linear polyethylene melts

Abstract

AbstractDiffusion coefficients of methane in linear polyethylene melts measured by simple sorption experiments are from 1.5 × 10−5 to 3.6 × 10−5 cm.2/sec. between 140.0 and 188.3°C. These diffusion coefficients are one‐third to one‐half those of methane in branched polyethylene melts at these temperatures. Solubilities of methane in branched and linear polyethylene melts are similar, approximately three molecules of methane per one hundred methylene units at 250 atm. partial pressure methane between 140.0 and 188.3°C. Temperature coefficients of solubilities of methane in branched and linear polyethylenes differ in that the solubility of methane in linear polyethylene melt appears to go through a minimum with temperature between 140.0 and 162.8°C. These differences in diffusion coefficients and temperature coefficients of solubilities are consistent with the presence of greater order in linear polyethylene melt than in branched polyethylene melt.