Properties of ultra-high-molecular-weight polyethylene with a structure modified by plastic deformation and electron-beam irradiation

摘要

To improve the functional properties of polyethylene in a polymer-metal kinematic system, ultra-high-molecular-weight polyethylene (UHMWPE) was subjected to light deformation by uniaxial compression [permanent true strain (e _f) = 0.14-0.32] and postdeformation electron-beam irradiation (with a dose of 26-52 kGy). X-ray examinations demonstrated that no significant reorientation of the lamellar structure occurred upon compression. The textures of all of the samples, except for the sample deformed at e _f = 0.32, were nearly random. In the exception, a very weak axial texture developed. However, the treatment applied (deformation and electron-beam irradiation) significantly changed the structure of the material. A considerable increase in the crosslinked fraction and the crystalline band absorption in the Fourier transform infrared spectra were observed in the modified samples. This indicated a noticeable increase in the degree of spatial ordering within a structure, although the overall crystallinity increased only slightly. The effect of such restructuring was evidenced by microscopic observations of the near-surface layer of the UHMWPE samples subjected to unidirectional sliding interaction with a CoCr alloy for 100 h (in a block-ring tribological system). It was found that for the predeformed (e _f = 0.14-0.21) and electron-irradiated (dose of 52 kGy) samples, the operational load imposed on the system resulted in a considerable reduction in the thickness of the plastically deformed near-surface layer and in a decreasing amount of lamellae oriented flat-on compared to the neat unmodified UHMWPE subjected to the same test. The recorded tribological wear (mass decrement) decreased up to fivefold in comparison to that of the initial material.