聚乙烯土工膜专用料链结构研究

Study on Branch Structure of Polyethylene Specially Used for Geomembranes

对2种高密度聚乙烯(PE-HD)土工膜专用料TR131和DQTG3912,在分析其力学和热力学性能的基础上,采用升温淋洗分级与连续自成核退火联用技术对支链结构及分布进行了系统表征,并与产品的力学性能相关联。高温碳谱核磁共振分析表明,DQTG3912比TR131具有更高的共聚单体插入量,支化度分别为6.7个/1000C和5.9个/1000C;DQTG3912低温级分的片晶厚度较高,高温级分片晶厚度较低;表明DQTG3912样品虽然含有较多的短支链,但在更容易插入的低相对分子质量处的分布较少,而在高相对分子质量处分布较多,更接近理想的短支链分布,有利于形成分子链间的系带分子,增强拉伸强度及耐环境应力开裂性能;产品力学性能的表征结果与链结构的分析相符。

Two commercial high-density polyethylene(PE-HD) materials specially used for geomembranes, TR131 and DQTG3912, were investigated comparatively in terms of their mechanical properties and chain structure. The HT 13C-NMR characterization result demonstrated that DQTG3912 had more short chains than TR131. The crystallinity of TR131 was analyzed by means of temperature rising elution fraction and successive self-nucleation and annealing, and the results indicated that TR131 had a lower degree of crystallinity. TR131 was found to have a higher relative content of low temperature fractions that DQTG3912, indicating a higher content of short-chain branching(SCB). DQTG3912 has less SCB at the low molecular weight parts but more SCB at the high molecular weight parts, which facilitated the formation of tie molecules and therefore improved its mechanical properties and resistance to environmental stress crack. The mechanical characterization results of DQTG3912 show good agreement with the analysis of its chain structure.