Radiation-induced effects on micro-scratch of ultra high molecular weight polyethylene biocomposites

Sterilization of ultra-high molecular weight polyethylene (UHMWPE) based composites used for acetabular cup liner via UV or gamma-irradiation before surgery is inevitable. Thus, understanding the alteration of mechanical properties and wear resistance of cup liner via irradiation process requires investigation. This paper aims to understand the effect of UV (0.03 J/cm2) and gamma (25 kGy) irradiation on mechanical properties and scratch resistance of compression molded UHMWPE composites reinforced with alumina (Al2O3), hydroxyapatite (HAp) and carbon nanotubes (CNTs). After irradiation, nearly 100% increased crystallinity of polyethylene, due to recrystallization, helped in enhancing the hardness and elastic modulus by ~1.5 times compared to that of as-processed UHMWPE (Hardness: ~70 MPa and Elastic modulus: ~1.25 GPa). The recrystallization was not favored by the presence of nano-reinforcements in irradiated UHMWPE based nanocomposites, and caused deterioration in the mechanical properties. The micro-scratch results revealed the remarkable wear resistance (i.e., 1.5 to 2 times lower wear rate) of irradiated samples than that of as-processed samples. Mouse fibroblast L929 in vitro cell culture test confirmed the cytocompatibility of irradiated samples. This study indicated that the UV and gamma irradiated UHMWPE nanocomposites are the challenging candidates as acetabular cup liner.