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SYNOPSISLow-density polyethylene (LDPE) is the most widely used plastic material in the filmpackaging industry. To improve its tensile strength and elongation, it is blended with linear LDPE. Three commercial samples of LDPE, which were found to give different performances in the sealing strength of films prepared from their blends, have been evaluated for their molecular weight (MW) , molecular weight distribution (MWD) , and long-chain branching by high-temperature size exclusion chromatography (SEC) and SEC coupled with a multiangle laser light-scattering (MALLS) detector. It has been shown that the differences in MW and MWD that remain unnoticed by conventional SEC are detected by SEC/MALLS. Wide MWD and a low weight-average MW of the resin has been found to favor film-sealing strength.

SYNOPSISThree commercial injection-molding-grade HDPE samples were evaluated for their properties. It was found that their impact property determined in the laboratory does not bear a simple correlation with the actual performance. The HTSEC study, undertaken to evaluate these samples, revealed that they differ significantly in z-average and z + 1-average molecular weights. This difference is attributed to the presence of a small amount of a very high molecular weight fraction and is responsible for the variation in the performance. 0 1996 John Wiley & Sons, Inc.