马来酸酐/苯乙烯熔融接枝无规共聚聚丙烯的流变及结晶行为

Rheology and Crystallization of Maleic Anhydride/Styrene Melt Grafted Random Copolypropylene

采用熔融接枝法制备了马来酸酐和苯乙烯多单体熔融接枝无规共聚聚丙烯(MPP),动态流变测试表明无规共聚聚丙烯(PPR)在接枝过程中生成了长支链。以差示扫描量热法(DSC)和Avrami方程分析了PPR及MPP的等温结晶行为,考察了马来酸酐的相对接枝率对MPP等温结晶动力学的影响。结果表明,MPP的结晶速率明显大于PPR,MPP接枝率越高,结晶速率越大。PPR和MPP在较高温度下等温结晶时结晶过程受成核控制,长支链的存在可以促进MPP晶核的形成,从而加快结晶速率。偏光显微镜测试结果显示长链支化结构起到促进异相成核和细化晶粒的作用,随着接枝率的增大,MPP晶粒尺寸越小。

Maleic anhydride/styrene melt grafted random copolypropylene(MPP)was prepared by multi-monomer melt grafting.Investigation on dynamic rheological properties of MPP indicates the existence of long chain branched structure.Isothermal crystallization behavior of PPR(random copolypropylene)and MPP was measured using differential scanning calorimetry(DSC)and the kinetics of isothermal crystallization was analyzed with Avrami equation.Effects of relative grafting degree of maleic anhydride on the kinetics of isothermal crystallization of MPP were examined.The results show that MPP crystallization rate is higher than that of PPR,and it increases with the increase of grafting degree.The isothermal crystallization of PPR and MPP is controlled by nucleation rate at high temperature region.The long chain branched structure can promote nucleation formation of MPP,which results in the increase of crystallization rate.The results of polarized light microphotographs verify that the long chain branched structure can promote heterogeneous nucleation and decrease crystal size.The crystal size of MPP decreases with the increase of grafting degree.