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 poly(1,2-butadiene) prepared by melt blending were crosslinked at 180-degrees-C and then studied by gel content measurements, size exclusion chromatography of the soluble fraction, infra-Ted spectroscopy measuring the vinyl content, elastic modulus measurements of the crosslinked melt and differential scanning calorimetry to determine the mass crystallinity of the crosslinked polymer. The kinetics of the crosslinking reaction was recorded by differential scanning calorimetry. The addition of poly(1,2-butadiene) to branched polyethylene had a significant effect 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 exothermal heat of the crosslinking reaction and a moderate decrease in crystallinity were observed on addition of poly(1,2-butadiene). The crosslinking reactions also involved a transformation of the vinyl groups leaving only 7% of them in the crosslinked blends.