结晶分级和分析型升温淋洗分级表征聚烯烃

用结晶分级(CRYSTAF)法和分析型升温淋洗分级(A-TREF)法对几种聚烯烃试样的分子链结构进行了表征,研究了降温速率对分级结果的影响,比较和分析了两种分析方法的适用性。实验结果表明,为消除相对分子质量对分级结果的影响,对于聚乙烯试样,A-TREF法应选用小于0.1℃/min的降温速率,而CRYSTAF法则可选用较快的降温速率(0.1～0.2℃/min);对于聚丙烯试样,CRYSTAF法和A-TREF法均可选用0.1～0.2℃/min的降温速率。两种分析方法对同一个试样有相似的级分分布曲线。实验结果还表明,聚烯烃试样的CRYSTAF曲线和A-TREF曲线有一定的指纹特性,结合甲基检测器的信息,两种分级方法还可用于共混聚烯烃的分离和鉴定。

Crystallization Analysis Fractionation and Analytical Temperature Rising Elution Fractionation for Characterization of Polyolefins

Crystallization analysis fractionation(CRYSTAF)and analytical temperature rising elution fractionation(A-TREF)were used in characterization of several polyolefins.Effects of cooling rate on the fractionation results were studied.A characterization comparison between CRYSTAF and A-TREF in analyzing the composition distribution of polyolefins was given.For polyethylene,it was found that the cooling rate of TREF should be lower than 0.1℃/min to eliminate influence of relative molecular mass on the fractionation,but cooling rate of CRYSTAF could be 0.1-0.2℃/min.For polypropylene,the cooling rates of both A-TREF and CRYSTAF could be 0.1-0.2℃/min.The similar distribution curves were obtained by using the two methods for polyethylene or polypropylene. It was showed that the fraction curves of polyolefins possessed fingerprint feature and the two methods could be used in identification of unknown polyolefin blends by means of a methyl detector.