REAL-TIME ANALYSIS OF THE THERMAL-OXIDATION OF POLYOLEFINS BY FT-IR EMISSION

Quantitative FTIR-emission spectroscopy was applied to investigate the real-time thermal oxidation of polyolefin samples and shown to be a useful method for studying polymer degradation. The high sensitivity of the technique was demonstrated by studying the oxidation of individual pressed polypropylene (PP) and high-density polyethylene (HDPE) reactor powder particles and microtome cuttings of crosslinked polyethylene (XLPE). A detailed analysis of the growth in carbonyl bands during the degradation showed no changes in the product distribution with time. Secondary oxidation products, such as gamma-lactones in the case of polypropylene, were observed from the onset of the degradation, which is consistent with a model of oxidation occurring in localized zones with high reactivities. Differences in the oxidation sensitivity of these materials were identified and attributed to variations in the stability of the PP particles, catalyst residues in the HDPE and the degree and method of crosslinking of the XLPE.