Eminent differences in cryogenic toughness of ultra-high molecular weight polyethylene with different entanglement densities

It is generally believed that the ultra-high molecular weight polyethylene (UHMWPE) performances are closely related to its molecular weight. However, when we sintered two brands of UHMWPE powders with similar molecular weights, GUR 4012 and GUR 400 Fine, we found they demonstrate eminent differences in cryogenic properties. Particularly, the cryogenic impact strength of GUR 4012 is 236% higher than that of GUR 400 Fine. To explain such an amazing phenomenon, we characterized UHMWPE microstructures and investigated the structure-property relations through scanning electron microscopy, x-ray scattering diffraction, differential scanning calorimeter, and dynamic mechanical analysis. We observed only a slight difference in crystallization behaviors between them, but the entanglement density of GUR 4012 is much higher than that of GUR 400 Fine. Accordingly, we put forward a potential mechanism to analyze the eminent differences in cryogenic impact strengths. This work may promote our comprehension of the relation between the structure and performances of UHMWPE, which is conducive to promoting UHMWPE performance and broadening its industrial applications.