Studies on structure and properties of high-impact copolymerized polypropylene with high melt flow rate
To improve the rigidity-toughness balance of high-impact copolymerized polypropylene with high melt flow rate(IPC-J),the ethylene content and the ethylene content in ethylene propylene rubber(EPR)were increased to 12.4 wt%and 54 wt%,respectively,by combination with the high-impact copolymerized polypropylene(IPC-H)technology.Meanwhile,the molecular segment structures and aggregation morphologies of IPC-J,IPC-H,IPC-1,and IPC-2 were investigated.The results indicated that the EPR content of IPC-J increased from 19.4 wt%to 22.8 wt%,its weight av-erage molecular weight(Mw)decreased from 2.0×105 to 1.9×105 g/mol,its intrinsic viscosity increased from 1.80 to 1.86 dL/g,its molecular weight distribution index increased from 8.9 to 10.7,and the maximum Mw of EPR increased from 1.1×106 to 1.2×106 g/mol,compared to those of IPC-H.The relatively longer ethylene crystalline chains with a greater amount were beneficial to enlarging the dispersed particle size.This resulted in a transformation of the maximum proportion region from 0.3～0.6 to 0.6～0.9 μm,which promoted higher impact strength of 11.0 kJ/m² at 20℃and 5.7 kJ/m² at-20℃.The rigidity-toughness balance of the IPC with a high melt index were fully optimized through in-creasing the ethylene content and the ethylene content of EPR,according to the production technology for 300-kt/a poly-propylene without changing the Ziegler-Natta-type catalyst system.
impact copolymer polypropyleneimpact strengthcrystallizationsuccessive self-nucleation and annealing
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