CROSS-LINKING OF BINARY BLENDS OF BRANCHED POLYETHYLENE AND POLY(1,2-BUTADIENE) .1. MOLECULAR-STRUCTURE AND KINETICS

Blends of branched polyethylene with 2% (w/w) of dicumyl peroxide and different percentage concentrations (0-8% w/w) of a low-molar-mass pol y(1,2-butadiene) prepared by melt blending were crosslinked at 180-deg rees-C and then studied by gel content measurements, size exclusion ch romatography of the soluble fraction, infra-Ted spectroscopy measuring the vinyl content, elastic modulus measurements of the crosslinked me lt and differential scanning calorimetry to determine the mass crystal linity of the crosslinked polymer. The kinetics of the crosslinking re action was recorded by differential scanning calorimetry. The addition of poly(1,2-butadiene) to branched polyethylene had a significant eff ect on the crosslinking reaction, indicating semi-compatibility of the two polymers. A strong increase in gel content, a pronounced decrease in the molar mass of the soluble fraction, a strong increase in exoth ermal heat of the crosslinking reaction and a moderate decrease in cry stallinity were observed on addition of poly(1,2-butadiene). The cross linking reactions also involved a transformation of the vinyl groups l eaving only 7% of them in the crosslinked blends.