Synthesis and Properties of Composites of Ultra-High Molecular Weight Polyethylene with Carbon Fibres or Fibre Monocrystals

Abstract

Composite materials were synthesized from ultra-high molecular weight polyethylene and discrete modified and unmodified carbon fibres or fibre monocrystals of alkali titanates. The modified carbon fibres contained 1.2% w/w oxygen-containing functional groups, obtained by subjecting them to thermo-oxidative treatment in air at 1073 K for 60 min. The properties of the composites were studied as a function of the carbon fibre content (up to 12% w/w) and fibre monocrystal content (up to 6% w/w). Neither the modified nor unmodified carbon fibres showed any reinforcing effect on the tensile strength of the polymer matrix, and the fibre monocrystals showed only an insignificant effect at 0.5–1.0% w/w loading. Composites containing thermally activated carbon fibres or fibre monocrystals were found to have higher thermal resistance. UHMWPE composites containing 12% w/w carbon fibres showed good specific electrical conductance and thermal stability, as well as lower friction coefficient, temperature coefficient of expansion and shrinkage on heat treatment compared to ultra-high molecular weight polyethylene. Composites with 6% w/w fibre monocrystals had higher thermal stability, shrinkage and especially Vicat softening points than ultra-high molecular weight polyethylene.