Abstract: The behavior of thermooxidative degradation and heat resistance of polypropylene（PP）film while treated at 150 ℃. After 8 days of thermooxidative treatment, significant thermooxidative degradation of the PP film was observed. However, the behavior of thermooxidative degradation of the samples was diverse. Some of the samples became degraded seriously so that they were incapable of measuring in mechanical properties, whereas some remained relatively integrated in shape. After the thermooxidative treating, the percent of the mechanicallymeasurable sample was 32.2 %, but the ageing coefficients of yield stress and tensile strength were 93.3 % and 79.6 %, respectively.

Key words: polypropylene, thermooxidative degradation, mechanical property, morphology, very high temperature