COMPARISON OF THE OF MECHANICAL AND WEAR BEHAVIOURS OF DIFFERNT TYPES OF POLYETHYLENES AND THE EFFECT OF RADIATION CROSS-LINKING ON THESE BEHAVIOURS

Different kinds of polyethylenes dominate the polymer field due to their wide range of applications and properties. They are sometimes cross-linked to improve their properties such as high temperature resistance and wear behavior. Radiation cross-linking using high energy electron beam or g-radiation constitutes one of the most convenient methods. This study explores the difference in mechanical and wear behavior of different polyethylenes, and compares the effect of radiation cross-linking and radiation dose on these properties. Three different types of polyethylenes: low density (LDPE), high density (HDPE), and ultra-high molecular weight (UHMWPE) were studied. Cross-linking was carried out by high energy electron beam at room temperature, with radiation dose ranging from 0-600 kGy. The results show that the stress-strain curve of UHMWPE in unirradiated state is marked by extensive strain hardening resulting in excellent wear resistance. Unirradaited HDPE show extensive yielding and high strain to failure, with dry abrasive wear properties comparable to UHMWPE. Unirradiated LDPE on the other hand exhibit low strength and strain to failure, and comparatively high wear rate. UHMWPE has the highest cross-linking efficiency, while HDPE and LDPE show low cross-link densities. Cross-linking induces brittleness in the materials except in case of LDPE, and improves wear rate of LDPE and UHMWPE. However, the wear rate of HDPE increases with cross-linking.