Thermal Oxidation Degradation Mechanism of Polyethylene by FT-IR Imaging

The deterioration mechanism of polyethylene with increased temperature resistance (PERT) used for hot water supply plumbing was investigated. The deterioration in 120 degrees C air was analyzed by using FT-IR. The following results were found (1) Degradation begins from the place where orientation relaxes gently and the amount of antioxidants decreases. The degradation by oxidation starts from surface. It advances along the surface, but does not advance that much into the bulk. (2) The progress of surface deterioration can be evaluated by the ratio acid to aldehyde peak of the carbonyl group, (3) It is necessary to evaluate not only the amount of carbonyl groups, at around 1600 cm(-1) but also its type (acid or aldehyde). The above result correlate with the results of tensile-strength tests and thermal measurements. The deterioration process of PERT can be analyzed more clearly by the FT-IR imaging method and visualization in two dimensions.