升温淋洗分级研究聚丙烯流延膜专用料的微观结构及热学表征

采用升温淋洗分级技术分离了2种聚丙烯流延膜（CPP）专用料（CPP1、CPP2），通过红外光谱仪、差示扫描量热仪和高温凝胶色谱对2种样品的链结构、熔融和结晶行为进行了表征，确定了产品各级分的分子结构信息。结果表明，对于低温（<100 ℃）级分，CPP1样品中其含量为9.29 %（质量分数，下同），CPP2样品中其含量为26.29 %；对于高温（≥120^{℃）级分，CPP1样品中其含量为3.16 %，CPP2样品中其含量为0.18 %；CPP1样品的120和140 ℃级分中均含有较高的乙烯（乙丙嵌段共聚物）含量，而CPP2样品的高温级分极少；CPP2样品中各级分的分子量几乎均高于CPP1样品中的相应级分，且分子量分布较宽；CPP1样品有2个熔点，127.2 ℃处的熔点源于较短的PP序列以及乙丙嵌段共聚物中的PE嵌段，148.4 ℃处的熔点源于高等规的PP序列；由不同长度的PP序列熔融导致CPP2样品有2个较高的熔融温度，熔融曲线在139.1 ℃出现肩峰，在150.7 ℃出现主要熔融峰。}

Microstructure and thermal characterization of polypropylene special material for cast films through temperature rising elution fractionation

Two types of cast polypropylene special materials， CPP1 and CPP2， were separated using a rising elution fractionation technology， and their chain structure and melting and crystallization behavior were characterized using infrared spectroscopy and differential scanning calorimeter. High?temperature gel permeation chromatography was performed to determine the comonomer content， sequence distribution， and the molecular weight and its distribution of the separated products. The results indicated that for the low?temperature elution components （<100 ℃）， the CPP1 and CPP2 exhibited low?temperature fractions of 9.29 wt%and 26.29 wt%， respectively. As for the high?temperature elution components （≥120 ℃）， the CPP1 presented a high?temperature fraction of 3.16 wt%， whereas the Sample CPP2 only showed a very small high?temperature fraction 0.18 wt%. In the CPP1， the fractions at 120 and 140 ℃ contain high ethylene content comprising of ethylene?propylene block copolymers. In the high?temperature fractions， the materials usually have higher isotacticity and crystallinity， which facilitates the enhancement in the rigidity of the resin. The CPP2 almost have higher molecular weights than the CPP1 in various fractions， and it showed a wider molecular weight distribution. The CPP1 contains two melting points at 127.2 and 148.4 ℃. The melting point at 127.2 ℃ was derived from the shorter PP sequence and the PE block in the ethylene?propylene block copolymer， whereas the melting point at 148.4 ℃ results from the higher isotactic PP sequence. The CPP2 exhibited a main melting peak at 150.7 ℃ along with a shoulder peak at 139.1 ℃ in its melting curve. The two higher melting temperatures were both caused by the melting of PP sequences with different lengths.