Synthesis of ultra-high molecular weight polypropylene homo(co)polymers
The physical,chemical,and mechanical properties of ultra-high molecular weight polypropylene(UHMWPP)are significantly different with those of ordinary isotactic polypropylene resins.At present the resin is synthesized mainly with traditional Ziegler-Natta catalysts and metallocene catalysts.The characteristics and potential of these two catalytic systems in preparation of UHMWPP are reviewed.The effects of reaction conditions,internal donors,and catalyst structure on properties of products are also analyzed.The research progress in synthesizing functionalized UHMWPP via copolymerization of propylene and polar monomers is discussed.Dimethylpyridine amine hafnium catalyst can be used to catalyze the copolymerization of propylene and substituted α-olefins under mild conditions to obtain high performance UHMWPP whose weight-average molecular weight is larger than 1.0×106.
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