The preparation of novel blends of Ultra High Molecular Weight Polyethylene with polymethacrylate based copolymers using supercritical carbon dioxide

Abstract

Supercritical carbon dioxide (scCO₂) was utilized to impregnate ethyl methacrylate (EMA) and propyl methacrylate (PMA) monomers within an Ultra High Molecular Weight Polyethylene (UHMWPE) matrix where they were subsequently copolymerised in situ. The ratio of EMA to PMA was varied in the monomer feedstock in order to ascertain the effect on the copolymer produced. The blends produced were shown to contain copolymers of poly(ethyl methacrylate) (PEMA) and poly(propyl methacrylate) (PPMA) with a ratio dependent on the feedstock monomer ratio. Dynamic Mechanical Analysis (DMA) demonstrated that the Young's Modulus of the materials could be controlled by the blending process. NMR, DSC, GPC and FTIR imaging was used to characterize the blends, showing the copolymer composition, thermal properties, molecular weight and location within the UHMWPE. Surprisingly, the molecular weight of the blended polymethacrylate is observed to be an order of magnitude higher than that formed outside the UHMWPE. The novel blended materials produced by this technique are not formed in the absence of scCO₂ and cannot be fabricated by conventional methods.