Morphology Of Ultrahigh Molecular Weight Polyethylene Research Articles

Influence of laser-induced surface carbonization on the tribological properties of UHMWPE in a seawater environment

The influencing mechanism of laser treatment on the tribological behavior of ultrahigh molecular weight polyethylene (UHMWPE) in a seawater environment was studied. The relation between the surface chemical composition and morphology of UHMWPE under different laser processing parameters and tribological properties in seawater environment was obtained. Oxidation and amorphization occurred when UHMWPE was laser-treated at relatively low-power densities (1.92 × 105 and 3.94 × 105 W/cm2), causing the slightly increase in wear rate of UHMWPE. Carbonization occurred after relatively high-power densities laser treatment (6.01 × 105, 8.12 × 105 and 1.00 × 106 W/cm2), causing significantly increase in wear resistance and decrease in friction coefficient. The laser-induced carbonization products were mainly composed of amorphous and graphitic carbon, which served as a solid lubricant during friction, thereby significantly improving the tribological properties of UHMWPE in the seawater environment. A method of laser-induced carbonization was proposed to improve the tribological properties of polymer materials in a seawater environment. Controlling the degrees of surface oxidation and carbonization of UHMWPE effectively regulated its tribological properties in seawater environments.

Radiation induced modifications in ultra-high molecular weight polyethylene

The effect of proton irradiation dose on the morphology of ultra high molecular weight polyethylene (UHMWPE) was studied. The radiation dose was varied from 0.09402 to 0.87 Mrads. The thermal behavior of the irradiated samples was investigated by submission to two heating cycles. The proton irradiation produces morphological changes in the mole fraction of crystallizable units, sequence length distribution, and crystallite thickness and distribution. The type of morphological changes is dependent on irradiation dose and thermal cycle. The low proton radiation dose produces only slight changes in the morphology of UHMWPE. More pronounced morphological changes are observed for the higher proton radiation dose.

Solid-state n.m.r. studies of crystalline phases in gel-spun ultrahigh molecular weight polyethylene

Gel-spun ultrahigh molecular weight polyethylene (UHMWPE) was examined by advanced solid-state 13C n.m.r. techniques to extract detailed information on the morphology and nature of the crystalline phases. Two partially overlapping resonances separated by 1.5 ppm in the 13C magic angle spinning n.m.r. spectrum have been assigned to monoclinic and orthorhombic crystalline phases. To analyse better the small amount of monoclinic phase, a 13C chemical shift filter was employed to suppress partially the dominant orthorhombic signal. The monoclinic phase exhibits a slightly smaller chemical shielding anisotropy of 27 ppm with chemical shift principal tensor values of 50, 36.5 and 16 ppm as compared to a shielding anisotropy of 30 ppm and principal tensor values of 50, 35.5 and 13 ppm for the orthorhombic phase. Additionally, a minor fraction of interface was detected arising from heterogeneous molecular packing. Both crystalline phases reveal an extremely high degree of order, with 〈 p 2〉 around 0.94. Whereas the conformations of the chains in the non-crystalline regions of both gel-spun and melt-spun polyethylene are alike, the mobility of the former is largely reduced. The morphology of UHMWPE is compared with that of melt-spun polyethylene.