Effects of mechanical drawing on gas transport in an emulsion acrylic multipolymer

A study was conducted on the gas sorption and transport properties of a multiphase commercial acrylic polymer trade‐named Korad ACV before and after subjecting the polymer to mechanical drawing operations. The Korad system is an emulsion‐polymerized amorphous composite comprised of a glassy, predominantly PMMA matrix phase and a ply(butyl acrylate)‐dispersed phase surrounded by a PMMA/PBA copolymer shell. Large increases (up to eightfold) in permeability P to several gases were observed upon drawing Korad. The observed changes in the permeability to He, Ar, N 2 , and CH 4 on drawing were correlated with the draw ratio, drawing temperature, and molecular diameter of the gas penetrant. Most of the increase in permeability occurred at low draw ratios (1–2). The increases in P were most dramatic for drawing temperatures below or near the T g of the matrix phase (about 90°C) and were quite small for drawing temperatures 30°C or more above the matrix T g . The extent of the permeability increase also depended on the gas, being greatest for CH 4 and essentially imperceptible for He. The changes in permeability behavior were interpreted in terms of a morphological transformation in the phase of the drawn Korad, which causes the originally dispersed rubber particles to assume a more continuous character. The behavior of the composite was modeled by the Takayanagi and Nielson treatments of two‐phase composite systems. Volumetric, thermal, mechanical, and viscoelastic properties were measured for the as‐received and processed Korad films to elucidate physical changes in the drawn polymer.