Improvement of Thermal and Photo Stability of Isotactic Polypropylene by the Incorporation of Comonomer

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With the aim of clarifying the effect of a small ethylene incorporation (5.3 mol%) on the thermal stability of one PP chain and photo stability of PP solid, homo isotactic PP (hPP) and ethylene-propylene random copolymer (rPP) were studied in respect of thermal and photo degradation. The thermal dega dation was performed under a dilute solution of trichlorobenzene. The decreasing in rate of molecular weight of the degraded rPP was slower than that of the degraded hPP, suggesting that the stability of one PP chain was improved by the ethylene incorporation. Whereas, the photo degradation of rPP was performed by a film sample having the same crystallinity (56 vol/%) as the hPP's. The formation rate of hydroperoxide and carbonyl groups in degraded rPP film increased against irradiation time as well as those of degraded hPP. However, those in the irradiated rPP were almost constant over 96 h. Also the molecular weight of irradiated rPP did not change over this time. This behavior implied that the degradation reaction cycle was stopped. It was found that the ethylene incorporation caused the decreasing in rate and the changing pathway of PP degradation reaction.
マテリアルライフ学会の論文