聚丙烯与三单体固相接枝物的等温结晶行为

采用固相接枝法合成聚丙烯(PP)与3种单体(马来酸酐、甲基丙烯酸甲酯和丙烯酸丁酯)的固相接枝物,利用傅立叶变换红外光谱研究接枝物的结构,通过差示扫描量热法和偏光显微镜研究固相接枝物的等温结晶行为,采用Avrami方程研究固相接枝物的等温结晶动力学.研究结果表明,接枝物的Avrami指数n和PP的相近,在0~3之间,说明接枝物存在混合式的成核生长方式.接枝支链充当异相成核剂,提高了成核速率,降低了结晶活化能;同时,接枝支链阻碍了PP基体的结晶进程,延长了接枝物完成结晶的时间.PP和PP接枝物结晶参数的拟合值与实验值基本一致,说明Avrami方程能有效地描述三单体固相接枝物的等温结晶行为.

Isothermal Crystallization Behaviour of Ternary-Monomer Solid-Phase Graft Polypropylene

Ternary-monomer solid-phase graft polypropylene (PPTM) was synthesized by the solid-phase grafting of maleic anhydride,methyl methacrylate and butyl acrylate onto polypropylene(PP).Then,the structure of PPTM was investigated by means of Fourier infrared spectroscopy,the isothermal crystallization behaviour of PPTM was studied by using the differential scanning calorimetry and the polarizing microscope,and the isothermal crystallization kinetics of PPTM was revealed via Avrami equation.The results show that(1) the Avrami index n of PPTM,which approximates that of PP,is within the range of 0 to 3,indicating that PPTM has a complex nucleation;(2) the grafted branch chains act as the heterogeneous nuclei,thus increasing the nucleation rate and decreasing the activation energy of crystallization;(3) the grafted branch chains hinder the crystallization of the PP chains,thus delaying the PPTM crystallization;and(4) the fitted isothermal crystallization parameters of PP and PPTM prove to be consistent with the experimental data,which indicates the effectiveness of Avrami equation in describing the isothermal crystallization behaviour of PPTM.