Impact Resistance Mechanism of Ultra-high Molecular Weight Polyethylene Molded Sheet

Ultra-high molecular weight polyethylene(UHMWPE)is an high performance engineering plastic with superior impact resistance,and the studies about its synthesis,processing and application have been a hot topic in modern polymer science,however,the mechanism behind its superior impact resistance is still unclear. In this work, four UHMWPE samples with viscosity average molecular weight around 5x10(6) and impact strength from 54.7 to 152 kJ/m(2) were studied in order to reveal the impact resistance mechanism of UHMWPE. It is found that under the same compression molding conditions,the four UHMWPE samples have the same crystal form,similar crystallinity and lamellar thickness. During the impact strength test,the UHMWPE sheets show a characteristic repetitive "extension-fracture"anti-impact behavior,and the number and width of extended bands are positively correlated with the impact strength. It is also discovered that the entanglement density of the amorphous phase is negatively and linearly correlated with the impact strength with a goodness-of-fit as high as 0.9. Thus it can be concluded that control. ling the entanglement of UHMWPE during its synthesis and processing procedure is really crucial to the impact strength.