Determination of Low Density Polyethylene Water Permeability, Transport Activation Energy, and Mechanical Properties after Thermal Oxidation and Immersion in Water

Abstract

Low Density Polyethylene (LDPE) thin film was exposed to oxygen gas overpressure and water. in a Parr Instruments pressure vessel at four temperatures 22, 50, 70 and 80°C; and, at 30 and 50 psi initial oxygen pressures. Sheet polypropylene (PP) and high-density polyethylene (HDPE) as well as injection molded HDPE, HDPP, and LDPE dogbones were exposed at 70°C and 30 psi initial oxygen pressure. Immersion of LDPE films was done under and above water at 80°C and 50 psi initial oxygen pressure. Permeation cup tests were done to determine the permeability of water vapor across the LDPE film at 60, 70, and 90°C. The extent of oxidation and functionality was monitored using ATR-FTIR and was consistent with previous work on polyethylene-oxygen reaction pathways. The permeability of the LDPE films and carbonyl content increased linearly with temperature, oxidation time, and oxygen pressure. The dogbones studied showed little change in mechanical properties.