茂金属聚乙烯薄膜晶点的组成及形成原因

Composition and Formation of Crystal Point of Metallocene Polyethylene Film

采用凝胶渗透色谱仪(GPC)、差示扫描量热仪(DSC)、偏光显微镜以及红外光谱等分析手段,从原料的分子链结构分析了茂金属聚乙烯薄膜晶点的组成及其形成原因。结果表明,茂金属聚乙烯薄膜晶点的结晶形态与无晶点的正常薄膜的不同,构成晶点的晶体尺寸均匀性远不如无晶点的正常薄膜,这是因为晶点中含有类似于纤维状的晶体,这种晶体先结晶,导致随后形成的晶体在此处生长不均匀。此外,分子链上的端基双键(RCH CH 2)在吹膜过程中引起的分子间交联和分子链中存在的亚甲基序列较长的规整结构,是形成类纤维状晶体的主要因素,而较长亚甲基序列的规整结构是由于共聚单体分布不均匀引起的。

By means of gel permeation chromatography(GCP),differential scanning calorimetry(DSC),polarizing microscope and infrared spectroscopy,the composition and formation of crystal point of metallocene polyethylene films were analyzed from the molecular chain structure of the raw materials.The results show that the crystalline morphology of the crystal point of metallocene polyethylene film is different from that of normal film,and the uniformity of the crystal size constituting the crystal point is far lower than that of normal film.The reason is that the crystal point contains fibrous crystals,in which the fibrous crystals crystallize first,resulting in the uneven growth of the subsequently formed crystals here.In addition,the intermolecular cross-linking are caused by the end group double bond on the molecular chain(RCH CH 2)in the film blowing process and the regular structure of the longer methylene sequence in the molecular chain are the main factors for the formation of fibrous crystal,while the regular structure of the longer methylene sequence is caused by the uneven distribution of comonomers.