SiO_2-MWNTs/聚乳酸复合材料的冷结晶动力学及球晶形态

为研究多壁碳纳米管(MWNTs)对聚乳酸(PLA)冷结晶动力学和球晶形态的影响,分别以PLA和表面包覆纳米SiO2并接枝硅烷偶联剂的纳米SiO2改性MWNTs(SiO2-MWNTs)为基体和改性剂,经溶液共混法制备了SiO2-MWNTs/PLA复合材料。采用DSC、偏光显微镜、Jeziorny模型和Johnson-Mehl-Avrami模型研究了复合材料的非等温冷结晶动力学和球晶形态。结果表明:SiO2-MWNTs可作为异相成核剂,能有效降低SiO2-MWNTs/PLA复合材料的冷结晶温度,提高晶核生成速率和晶体生长活化能。SiO2-MWNTs/PLA复合材料的冷结晶过程主要由成核作用控制,加入SiO2-MWNTs可同时提高复合材料的结晶速率和结晶度。冷结晶时,PLA球晶尺寸小于熔体冷却结晶时的,且SiO2-MWNTs含量对冷结晶球晶尺寸的影响远小于其对熔体冷却结晶球晶尺寸的。所得结论对优化PLA的结晶结构和性能、制备高性能PLA复合材料具有指导意义。

Cold crystallization kinetics and spherulitic morphologies of SiO2-MWNTs/polylactide composites

In order to investigate the effects of multi-walled carbon nanotubes (MWNTs) on the cold crystallization kinetics and spherulitic morphologies of polylactide (PLA), PLA and nano-SiO₂ modified MWNTs (SiO₂-MWNTs) which was surface-coated with nano-SiO₂ and grafted with silane couple agent were selected as matrix and modifying agent respectively to prepare SiO₂-MWNTs/PLA composites via solution blended process. DSC, polarized optical microscope, Jeziorny model and Johnson-Mehl-Avrami model were used to investigate the non-isothermal cold crystallization kinetics and spherulitic morphologies of composites. The results indicate that SiO₂-MWNTs can act as heterogeneous nucleating agent which decreases the cold crystallization temperature, increases the nucleation rate and the activation energy of crystal growth of SiO₂-MWNTs/PLA composites effectively. Cold crystallization process of SiO₂-MWNTs/PLA composites is mainly dominated by nucleation, and the addition of SiO₂-MWNTs can improve crystallization rate and crystallinity of the composites simultaneously. The spherulitic size of PLA which is cold crystallized is smaller than that of melt cooling crystallized. The influence of SiO₂-MWNTs content on cold crystallization spherulitic size is much smaller than that of it on melt cooling crystallization spherulitic size. The conclusions have guiding significance for optimizing the crystal structure and properties of PLA and preparing high-performance PLA composites.