多壁碳纳米管／聚碳酸酯复合材料玻璃化转变温度的研究

Investigation of the Glass Transition of Multi-Walled Carbon Nanotube/Polycarbonate Composites

碳纳米管(CNTs)自发现以来,由于其优异的物理、化学等性能使其在很多领域都有潜在的应用价值,尤其是作为高分子材料改性填料而备受关注。但到目前为止,CNTs填充对复合材料宏观性能影响的微观机理还不清楚,CNTs的加入对聚合物的微观结构产生什么样的影响,而微观结构又如何影响复合材料的宏观性能等,仍然是有待深入研究的重要课题。采用溶液共混-共沉淀的方法制备了聚碳酸酯(PC)/多壁碳纳米管(MWCNTs)复合材料;利用正电子湮没寿命谱仪研究了自由体积随温度的变化;利用三种不同的实验方法:正电子湮没寿命谱测量、动态力学热分析测量和示差扫描量热测量得到了复合材料变化趋势一致的玻璃化转变温度(Tg),都是随着碳纳米管含量的增加而降低。

Since carbon nanotubes （CNTs） were first discovered in 1990, due to its excellent physical properties, it has be- come a potential material in many fields, especially in the field of polymers filled with CNTs, which have received increasing attentions. Although significant progress in mechanical, thermal, electrical and rheological properties has been made in develo- ping nanocomposites with different polymer matrices, a general understanding for the mechanism has not yet emerged. In other words, how can the addition of nanofillers affect the microstructure of polymer？ And how can the microstructures affect the ma- cropropeties？ A major direction in the further development of nanocomposites is finding out the simple structure-property rela- tionship. In this report, polycarbonate （PC）/multi-walled carbon nanotube （MWCNT） composites have been prepared by so- lution mixing. The i^ffluences of temperature on the free volume of MWCNT/PC composites were investigated by positron anni- hilation lifetime spectroscopy （PALS）. Three methods, including PALS, dynamic mechanical analysis and differential scan- ning calorimetry were used to determine the glass transition temperature （ Ts） of PC/MWCNT composites. The experimental results indicated that the higher the MWCNT contents, the lower the Ts, which attributes to the large free volume hole and the enhanced polymer mobility in PC/MWCNT composites with higher MWCNT contents.