超临界流体制备PMMA/MWCNTs微孔发泡复合材料及其导电性能

Preparation of PMMA/MWCNTs Microcellular Foaming Composite based on Supercritical Fluid and Its Electrical Conductivity

通过溶液-熔融共混法制备聚甲基丙烯酸甲酯(PMMA)/多壁碳纳米管(MWCNTs)复合材料,辅以透射电子显微镜对MWCNTs在PMMA基体中的分散性进行表征,发现MWCNTs分散性良好,直径约为10 nm,平均长度约为200 nm。通过超临界流体发泡工艺对PMMA/MWCNTs复合材料导电网络进行调控,从而获得具有不同电导率的微孔发泡复合材料。采用扫描电子显微镜观察不同发泡工艺下复合材料的泡孔形貌并表征其发泡行为,研究了发泡工艺对不同MWCNTs含量的复合材料电导率的影响。结果表明,发泡温度从135℃增加至150℃,复合材料泡孔尺寸和发泡倍率增加,泡孔密度降低;保压压力从15 MPa增加至30 MPa,复合材料泡孔尺寸和发泡倍率降低,泡孔密度增加。PMMA/MWCNTs微孔发泡复合材料具有典型的逾渗现象,发泡温度增加对导电网络的形成起到抑制作用,而提高保压压力可促进导电网络形成。当MWCNTs质量分数为5%、发泡温度为145℃、保压压力为30 MPa时,复合材料的电导率达到0.19 S/cm。

The solution-melt blending method was employed to obtain the polymethyl methacrylate/multi-walled carbon nanotubes(PMMA/MWCNTs)composites.The dispersion of MWCNTs in PMMA matrix was characterized by transmission electron microscope.It is found that MWCNTs have good dispersion with a diameter of about 10 nm and an average length of about 200 nm.The conductive network of PMMA/MWCNTs composites was regulated by supercritical fluid foaming process for preparing microcellular foaming composites with different conductivity.Through using scanning electron microscope,the cell morphology of the composites under different foaming processes were observed and the foaming behaviors were characterized,the effects of foaming process on the conductivity of the composites with different MWCNTs content were studied.The results show that,as the foaming temperature increases from 135℃to 150℃,the cell size and expansion rate increase,the related cell density decreases.At the same time,the holding pressure increases from 15 MPa to 30 MPa,the cell size and expansion rate decrease,the related cell density increases.The conduction networks of PMMA/MWCNTs microcellular foaming composites show the typical percolation phenomenon.The formation of conductive network is suppressed by increasing foaming temperature,and promoted by increasing the holding pres-sure.When the content of MWCNTs is 5wt%,the foaming temperature is 145℃and the holding pressure is 30 MPa,the conductiv-ity of the composite reaches 0.19 S/cm.