Abstract: The molecular and crystalline structures of Lyondell Basel Company’s high density heatresistant polyethylene pipe resin 4731B were analyzed by solvent gradient classification combined with gel permeation chromatography(GPC), carbon nuclear magnetic resonance(13C-NMR), differential scanning calorimeter (DSC). It was found that the crystallinity was 63 %, the chip thickness was 31 nm; the molecular weight distribution was bimodal, MWD was 18.0, MW of low molecular weight part was 4.0×103~3.0×104, that of high molecular weight part was 3.0×105~6.0×105. Short branched chains evenly distributed in the higher polymer chains, comonomer content is more than 1.25 %. Ratio of high and low molecular weight components was (50~55)∶(45~50).

Key words: high density heat-resistant polyethylene, pipe resin, solvent gradient classification, molecular structure