PREPARATION AND CHARACTERIZATION OF ULTRAHIGH MOLECULAR-WEIGHT POLYETHYLENE AND POLYISOPRENE SOLVENT-CAST BLEND FILMS

This study covers the preparation of noncrosslinked and crosslinked so lvent-cast blend films of ultrahigh molecular weight polyethylene (UHM WPE) and polyisoprene rubber (PIR) and their mechanical, thermal, IR s pectroscopic, and morphological characterizations. Solvent-cast films of polymer blends with 0, 10, 20, 35, 50, and 65% PIR composition were prepared by vigorous stirring from a hot decalin solution. The films were crosslinked chemically by using acetophenone as a crosslinking ag ent under UV radiation. The mechanical properties, measured as ultimat e properties and tensile modulus, were found to decrease with PIR cont ent but crosslinking was found to enhance the ultimate strength and te nsile modulus. DSC results revealed that melting point of UHMWPE remai ns almost constant in blends. However, upon crosslinking, the melting point of UHMWPE is depressed almost 5 degrees C. We observed a similar trend in the enthalpy change of the melting of UHMWPE and the variati on of percent crystallinity in UHMWPE. Scanning electron microscopy (S EM) studies on the fractured surfaces of the blends showed that the fi brillar texture is present in both crosslinked and noncrosslinked blen ds. The crosslinking appeared to be through oxygen linkages, which are preferentially conjugated to double bonds, in addition to the possibl e carbon-carbon crosslinks. (C) 1998 John Wiley & Sons, Inc.