SUMMARY:Thermomechanical degradation of polystyrene (PS) at 180" and 250°C resulted in main chain scission and a small decrease in the molecular weight, as measured by inherent viscosity. The lower molecular weight was retained in the presence of maleic anhydride (MAH) although the latter was incorporated into the PS. The presence of benzoyl peroxide and dicumyl peroxide in the molten PS resulted in a significant molecular weight reduction, due to disproportionation of the internal radicals generated by hydrogen atom abstraction from the PS backbone. The extent of peroxide-induced degradation was greatly reduced in the presence of MAH which presumably added to the internal PS radicals before their disproportionation. The low MAH content of the reaction product despite the use of high concentrations of MAH and peroxides is attributed to the quenching of MAH excimers by PS. ZUSAMMENFASSUNG:Der

SynopsisThe reaction of molten HDPE with MAH at 215 and 250°C using di-t-amyl peroxide and t-butyl cumyl peroxide as catalysts yielded HDPE-g-MAH accompanied by crosslinked polymer. The formation of the latter, increased by the presence of MAH and insoluble in refluxing xylene, was prevented by the presence of electron donor additives, i.e., dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), and tri(nonylpheny1)phosphite (TNPP). A charge containing 0.0625-0.1258 catalyst, 5% MAH and 0.5% additive, all based on HDPE and added to the molten HDPE in four portions, resulted in gel-free polymer with an MAH content of 0.7-1.7%. HDPE-g-MAH with the least color was obtained with TNPP, followed by DMAC and DMSO. Notwithstanding the absence of gel in the HDPEg-MAH prepared from HDPE with a melt flow of 17 g/10 min, the carboxylated HDPE had a melt flow of 0.0-1 g/10 min, indicative of an increase in the molecular weight of the product. This is attributed to a coupling reaction between MAH radicals appended to the HDPE backbone (HDPE-MAH . ) and HDPE radicals formed as a result of hydrogen abstraction from HDPE by radicals from the catalyst and/or excited MAH.

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