抗冲共聚聚丙烯中二甲苯可溶物的链结构与性能研究

Investigation of the Chain Structure and Thermal Property of Xylene Solubles of Impact Polypropylene Copolymers

抗冲共聚聚丙烯(IPC)是聚丙烯与乙烯-α-烯烃共聚产物在反应釜内形成的原位共混物,乙烯-α-烯烃无规共聚物(橡胶相)作为聚丙烯增韧剂,增韧能力受其组成、玻璃化转变温度(Tg)的影响很大。目前工业界主要采用二甲苯可溶物来表征IPC中橡胶相的含量。该研究采用红外光谱(FTIR)、核磁共振(NMR)和热分析(DSC)等方法对两种不同催化剂制备的IPC的二甲苯可溶物,进行了组成、链结构及热性能对比研究,结果显示二甲苯可溶物中除了乙烯-丙烯无规共聚物外,还含有少量的具有可结晶乙烯序列的乙烯-丙烯多嵌段共聚物,且两个样品中的乙烯-丙烯多嵌段共聚物中可结晶乙烯序列长度存在差别;两个样品中乙烯、丙烯单元在分子链上无规分布的程度比较接近;丙烯序列PPP的含量相对低且乙烯共聚单元含量高的样品具有更低的Tg,这将有利于其对聚丙烯抗冲击韧性的提高。

Impact polypropylene copolymers （IPC） are irrsitu blends of polypropylene homopolymer and ethylene-trolefin copol- ymers formed in the reactor, which is a multiphasic complex material with isotactic polypropylene （iPP） as a matrix in which poly（ethylene-α-olefin） elastomeric copolymer is finely dispersed, and ethylene-α-olefin random copolymer （EPR） acts as an elas- tomer to improve the impact resistance properties of iPP at room temperature and low temperature. In the present, the content of xylene soluble is used to evaluate the content of EPR rubber phase in IPC. The content, the chain structure, and glass transition temperature （Tg） of EPR rubber are critical to the toughness of IPC. In the present report, Fourier transform infrared spectros- copy（FTIR）, nuclear magnetic resonance （NMR） and differential scanning calorimetry（DSC） were utilized to study the comono- mer content, chain structure and thermal property of xylene soluble of two IPC prepared by different catalysts. The results indi- cated that there are small amount of ethylene-propylene segmented copolymers containing short methylene sequence that is crys- tallizable in the xylene soluble in addition to the ethylene-propylene random copolymers. And the sequence length of crystallizable methylene group of ethylene-propylene segmented copolymers in these two kinds of xylene soluble is different. The random dis- tribution degree of ethylene and propylene monomer in the ethylene-propylene copolymers in these two kinds of xylene soluble is similar. The xylene soluble with lower content of PPP sequence and higher content of ethylene monomer has lower Tg, which will benefit the improvement of impact resistance property of polypropylene.