Surface Reaction of Ozone at High Concentration with Isotactic And Syndiotactic Polypropylene

The surface reaction of isotactic and syndiotactic polypropylene (I-PP and S-PP) films with ozone was studied with FT-IR spectroscopy with differential scanning calorimetry (DSC) and making use of 2,2,4-trimethylpentane as a model compound of PP chain segment. I-PP and S-PP were found reactive toward ozone, and it was found that I-PP being more crystalline than S-PP, reacts more slowly with O₃. In fact, the pseudo first rate constant of I-PP with ozone was k’_I-PP = 8.0 × 10^?6 s^?1 while that of S-PP with ozone k’_S-PP = 1.3 × 10^?5 s^?1. However, the DSC study has shown that the ozone attack on I-PP or S-PP films is not selective and simultaneously destroys the amorphous and the crystalline phases. The ozone treated I-PP and S-PP films are much less resistant to the combined thermal and oxidative degradation reaction than the unexposed films. Thus, ozone is a naturally occurring pollutant at the soil level which accelerates the ageing of I-PP and S-PP materials.