Mechanical behavior, microstructure and thermooxidation properties of sequentially crosslinked ultrahigh molecular weight polyethylenes

摘要

The aim of this study was to explore the impact of the sequential irradiation and annealing process on the microstructure, thermooxidation behavior and mechanical properties of GUR 1050 ultrahigh molecular weight polyethylene (UHMWPE) with respect to the postirradiation annealed material. For this purpose, the effects of a variety of irradiation and annealing conditions on microstructure and mechanical properties were investigated. Differential scanning calorimetry was performed to characterize melting temperature, crystalline content and crystal thickness, whereas transmission electron microscopy provided additional insights into crystal morphology. Thermogravimetric experiments in air served to assess thermooxidation resistance and changes associated to radiation-induced crosslinking. Fatigue properties were studied from three different approaches, namely short-term cyclic stress-strain tests, long-term fatigue experiments and crack propagation behavior. Likewise, three experimental techniques (uniaxial tensile test, impact experiments, and load to fracture of compact tension specimens) allowed evaluation of the fracture resistance. The present findings confirm sequentially crosslinked UHMWPE exhibited improved thermooxidation resistance and thermal stability compared to post-irradiation annealed UHMWPE. Also, the mechanical behavior, including the fatigue and fracture resistance, of these materials was generally comparable regardless of the annealing strategy. Therefore, the sequential irradiation and annealing process might provide higher oxidation resistance, but not a significant improvement in mechanical properties compared to the single radiation dose and subsequent annealing procedure.