MICROHARDNESS OF A PE / PE - COMPOSITE AND POLYETHYLENE GRADIENT MATERIAL

This paper presents characteristics of polyethylene gradient material and polyethylene fibre/polyethylene matrix composites determined by universal hardness tests. PE-samples with a gradient in molecular weight (MW) and polyethylene / polyethylene composites were characterised by light microscopy and microhardness measurements. The influence of molecular weight, molecular weight distribution (MWD), the morphology and the properties of the composites were studied. An increase in molecular weight of polyethylene in the graded samples leads to a decrease in hardness and indentation modulus. In the polyethylene homocomposites an increase in microhardness HUcorr and indentation modulus YHU can be observed with an increasing orientation of the molecular chains. The mechanical work indicated during the indentation procedure was investigated: partly consumed as plastic deformation work and partly set free as work of the reverse deformation. In this paper the results of mechanical tests will be discussed in view of the potential improvements in wear and durability of knee joint replacements.