method for improving the mechanical and processing properties of isotactic polypropylene

摘要

A crystallizable, linear head-to-tail high polymer of propylene is subjected to thermal degradation until the average degree of polymerization has been reduced to such an extent that on the completion of production of articles by a forming process involving heating the average degree of polymerization will have been reduced to a value corresponding to an intrinsic viscosity, measured in tetrahydronaphthalene at 135 DEG C., of from 0.8 to 1.8. The thermal degradation may be effected by heating at 250-350 DEG C. in the absence of oxygen or at 150-180 DEG C. in the presence of oxygen. A stabilizer may be present during the degradation or added at the end of the treatment. Up to 30% of amorphone polypropylene may be present with the crystallizable polymer. The product may be filamentary or laminar, and may be extrusion- or injection-moulded or calendered. Specifications 810,023 and 828,791 are referred to.