茂金属聚乙烯的短链支化结构不均匀性研究进展

Progress in the Research of Molecular Heterogeniety in Short-Chain Branched Polyethylene by Metallocene Catalyst

茂金属支化聚乙烯技术是聚烯烃工业发展史上最重要的技术进展之一,该类产品具有优异的抗穿刺、抗撕裂、抗冲击性质,在薄膜、重包装等领域具有广泛的用途,其力学性能与共聚单体的种类、含量及其在分子链上的分布有密切关系。本文从催化剂活性中心特点和聚合反应工艺条件两方面对聚合物结构的影响出发,阐述了茂金属聚乙烯短链支化结构不均匀性产生的原因,通过核磁共振、升温淋洗分级和热分级等表征支化不均匀性的研究方法,介绍了茂金属支化聚乙烯分子主链上共聚单体的序列结构组成及分布,以及共聚物的结晶性能等方面的差异。

Technology for branched polyethylene by metallocene catalysts was one of the most important advancements in polyolefin industry. Metallocene LLDPE was widely used in film and heavy duty packaging due to its high performance of anti-pierce and anti-impact. The property of m-LLDPE was highly related to the type, concentration and the distribution of comonomer incorporated. This review introduced the originality of the molecular heterogeneity in m-LLDPE from the point view of catalytic active center and the effect of the fluctuation in polymerization conditions. Method for molecular heterogeniety characterization in branched polyethylene by 13C NMR, TREF and DSC-SSA were discussed in detail to show the difference of the comonomer sequence composition, distribution and crystallization properties of the copolymers.