THE DETERMINATION OF THE REACTION RATES, WATER VAPOR PERMEABILITY, AND ACTIVATION ENERGY FOR THERMAL OXIDATION OF LDPE FILMS

摘要

To understand the mechanism of degradation ofplastics under environmental conditions, thermaloxidation of LDPE thin film from a single manufacturerwas studied. Oxidation was carried out in a pressurevessel with control at four temperatures(22,50,70 and80°C and at 30 and 50psi oxygen pressures. Cup testswere done to determine the permeability of water vaporacross the LDPE film at 60, 70, and 90°C. The extent ofoxidation was monitored using ATR-FTIR and thecarbonyl content calculated from the spectra. Bandscentered at 1711 and 1735 cm-1 was determined resultedfrom the carbonyl stretches. A broad band at 3100-3600cm-1 is attributed to O-H stretching and thefingerprint region (<1400 cm-1) shows evidence of C-Ostretches. The carbonyl content and permeability to watervapor increased with temperature, oxidation time, andoxygen pressure. Water permeation is a result of thedisruption of the semi-crystalline structure of the film toproduce amorphous regions within which the water vaporis more permeable. This study was a step in the directionfor determining a reliable model for the degradation andeventual failure of medium voltage power cables innuclear power plants (NPPs).