介观相分离对等规聚丙烯/烯烃嵌段共聚物共混体系相容性的影响

Effect of Mesophase Separationon the Compatibility of iPP /Olefin Block Copolymer Blends

研究了2种烯烃嵌段共聚物(OBC1和OBC2)与等规聚丙烯(iPP)的相容性,其中2种烯烃嵌段共聚物具有相近的软硬段组成,软硬段中辛烯含量接近,但分子量不同.通过对OBC线性黏弹性的研究发现高分子量的OBC1会发生较强的介观相分离,而在所研究的温度范围内,低分子量的OBC2保持均相.利用了液滴回缩和流变学的方法测量了2种iPP/OBC共混体系的界面张力,同时采用动态力学分析研究了共混物中组分玻璃化转变温度的变化,并通过自浓度模型估算了2种OBC与iPP互溶的溶解度.结果发现虽然OBC1与iPP的界面张力较高,但二者之间的相容性却优于OBC2与iPP的相容性,这很可能是OBC1分子量大,嵌段共聚物的强介观相分离所导致其与iPP相容性更好.对iPP/OBC共混体系结晶行为的研究也证实了相容性差异对共混物中等规聚丙烯结晶行为的影响.

The compatibility between olefin block copolymers （OBC1 and OBC2） and isotactic polypropylene （iPP） was studied in this work. The two OBCs have similar hard block content and octene content, but are different in molecular weight. The linear viscoelasticity of OBCs were systematically studied. It was found from linear viscoelasticity that 0BC1 with high molecular weight tends to exhibit strong mesophase separation,while OBC2 with low molecular weight is homogeneous in the studied temperature range. The interfaeial tensions between OBCs and iPP were measured by drop retraction and dynamic rheologieal method. Both methods have achieved consistent results for the interfacial tension of the blends. The interfacial tension between iPP/OBC1 is around 1.17 mN/m,which is larger than that between iPP/OBC2 （ about 0.3 mN/m）. The variation of glass transition temperature in iPP/OBC blends were also studied by dynamic mechanical analysis,and depressions in the glass transition temperature of iPP were observed in both blends,from which the solubility of OBCs in iPP was estimated by self-concentration model. It was found that although the interfaeial tension between OBC1 and iPP is larger, their miscibility is better. This is ascribed to the strong mesophase separation of OBC1. Further study on the crystallization of iPP in blends also justified the miscibility difference between iPP and the two OBCs.