Preparation and characterization of hybrid filler reinforced UHMWPE composites for artificial joint replacement

Abstract

This is a study of ultra-high molecular weight polyethylene (UHMWPE) reinforced with zinc oxide (ZnO) under various filler loadings (3, 7, 12, 18 and 25 wt.%) and hybridized with incorporation of chitosan (CS). Further development of the UHMWPE composite was via 3-APTES treatment of the ZnO particulates with silane as a coupling agent. All composite specimens were mixed via dry ball milling and prepared using hot compression molding. Additions of ZnO towards UHMWPE resulted in an increase of 28.99% in the ultimate tensile strength compared to unfilled UHMWPE with the optimum percentage (12 wt%) of ZnO. The addition of 12 wt.% ZnO also has significantly increase the wear resistance of tested composites, in accordance with the minimal weight loss. The flexural strength and modulus had a notably high improvement through ZnO addition up to 25 wt% as compared to pure UHMWPE. However, the incorporation of CS (1, 2, 3 wt%) in the optimum percentage (12 wt%) of UHMWPE/ZnO composites has slightly changed the properties of the hybrid composites where the addition of CS had resulted in lower flexural strength and wear resistance than that of 12 wt% ZnO UHMWPE composite but still higher than that of pure UHMWPE. The addition of ZnO to the UHMWPE matrix had lowered the melting temperature (Tm) of the composite but delaying the degradation temperature of the composite. Further investigation of dual filler incorporation was done by addition of CS to the UHMWPE/ZnO composite and resulted in reduction of the degree of crystallization, Xc, of UHMWPE. Chemical resistance was improved with higher ZnO content with a slight reduction of mass change after incorporation of CS. The hardness value increased with ZnO addition but higher incorporation of CS had lowered the hardness value. Effect of treatment on ZnO towards the properties of UHMWPE composite and hybrid resulted in a significant improvement compared to UHMWPE filled untreated ZnO on all properties on both UHMWPE composite and hybrid composites. The highest magnitude of change was seen in the tensile strength and wear resistance was at 12 wt.% of treated ZnO (tZnO) content. However, the flexural properties achieved highest point with incorporation of 2 wt.% CS towards UHMWPE/tZnO. Thermal stability was also achieved with more tZnO addition where the thermal degradation of UHMWPE was hindered around 7% for the T10% value. Ultimately, it was experimentally proven that the UHMWPE hybrid composite with CS—tZnO as fillers had best out in the terms of biocompatibility via Alamar Blue (AB) assay.