CORRELATION OF MECHANICAL AND CHEMICAL CHANGES IN GAMMA-IRRADIATED ULTRA-HIGH MOLECULAR WEIGHT POLYETHYLENE

摘要

Ultra-high molecular weight polyethylene (UHMWPE) is used in the manufacture of several products due to its excellent engineering properties -high tensile and impact strength, low friction coefficient, resistance to chemical attack and biocompatibility. It is well known that gamma irradiation introduces structural changes that may be detrimental to the integrity and performance of the polymer, limiting its useful life. Plates manufactured with commercial, general-grade, UHMWPE were exposed to several doses of gamma radiation at room temperature in air. The structural changes of the plates were investigated by gel content determination, mechanical testing (hardness, tension and impact), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), wide angle X-ray diffraction (WAXD), electron spin resonance (ESR) and scanning electron microscopy (SEM). Experimental results show crosslinking and an increase in crystallinity. More significant changes are observed in samples irradiated with higher doses: chain scission induced by oxidation changes the molecular structure, degrades the mechanical properties and changes the fracture mechanism from ductile to brittle.