Thermo-Oxidative Degradation of Molten State Polypropylenes with a Variety of Tacticity.

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Thermooxidative degradation of polypropylene (PP) s with a variety of tacticity was investigated in terms of various degradation factors, such as catalyst residue in the PP, molecular weight of the PP, and amount of oxygen existed. Heat treatment was typically carried out in the air at 200°C for 30min, at where the PP powder was varied into the molten state within several minutes. The catalyst residue and molecular weight had slight influence on the thermooxidative degradation of isotactic PP. Thermal stability of three polypropylenes (isotactic PP, atactic PP, syndiotactic PP) having similar molecular weight was investigated under the same conditions. Isotactic PP was degraded drastically compared with atactic PP and syndiotactic PP in the air. The thermal degradation of isotactic PP was depressed greatly under nitrogen. Existence of oxygen was found to induce the thermal degradation, even in syndiotactic PP. Thus, it was found that the influence of the tacticity and oxygen pressure was significant compared with that of the catalyst residue and molecular weight.
マテリアルライフ学会の論文