低密度聚乙烯长支链含量的测定

Determination of long branched chains in LDPE

针对低密度聚乙烯(LDPE)支化度计算困难的问题,采用旋转流变法及核磁共振碳谱(^(13)C-NMR)法分别计算Basell管式法装置生产的系列LDPE的长支链含量。结果表明:随着LDPE熔体流动速率的提高、相对分子质量的降低,其长支链含量降低;探讨了旋转流变法和^(13)C-NMR法的差异,采用^(13)C-NMR法计算得到的长支链数差异小,无法准确表征支化结构接近的工业化LDPE各批次间的差异;采用旋转流变法测定的LDPE长支链数具有检测时间短、长支链敏感性高的特点,适合工业上快速、准确地表征LDPE支化结构。

Low density polyethylene （LDPE）produced by Basell tubular plant were selected for the branching calculation of LDPE with the help of the rotary rheometer and nuclear magnetic resonance （13C-NMR） respectively. The results show that with the increase of melt flow rate and the decrease of relative molecular weight, the content of long branched chains in LDPE is decreased. The difference between two calculation methods were investigated. The slightly different data obtained from 13C-NMR can＇t reflect the differences accurately between the industrial products of each batch with similar branched structure; rotary rheometer used for long branched chain calculation features short detection time and high sensitivity, which make it suitable for industrial characterization of branched structure of LDPE accurately and rapidly.