碳纳米管／PMMA／PVAc复合膜的制备及其导电性能研究

Microstructure and electrical resistance of carbon nanotubes/PMMA/PVAc composite film

用竖式炉流动法，以二茂铁为催化剂，硫为助催化剂，苯为碳源制备碳纳米管（CNT），反应温度为1100-1200℃，碳纳米管的外径为20-40nm，内径10-30nm，长度5-20μm，并在2800℃对碳纳米管进行石墨化处理。用超声分散和溶液浇铸工艺制备碳纳米管，聚甲基丙烯酸甲酯（PMMA）／聚醋酸乙烯酯（PVAc）复合膜和石墨化碳纳米管／PMMA／PVAc复合膜，石墨化碳纳米管复合膜的导电性能明显优于碳纳米管复合膜，石墨化碳纳米管／PMMA／PVAc复合膜和碳纳米管／PMMA／PVAc复合膜的渗流阈值分别为2．5％和5％（质量分数），碳纳米管／PMMA／PVAc复合膜是很好的气敏候选材料。

The carbon nanotubes were prepared by catalytic decompose of benzene using floating transition method at 1100-1200℃. Benzene was used as carbon source and iron as catalyst with sulfur. The carbon nanotubes axe straight with diameter 20-40 nm, internal diameter 10-30 nm and length 5-20μm. The composite films of poly（methyl methacrylate） （PMMA）, poly（vinyl acetate） （PVAc） and carbon nanotubes were prepared by solution casting method. The carbon nanotube （CNT） and graphitized carbon nanotube （GCNT） were employed as conductive fillers in the composite films. The best way to produce the carbon nanotube/PMMA/PVAc composite film with conductive network was dispersing carbon nanotubes in PMMA and PVAc by ultrasonic and solution casting. The conductivity of the GCNT/PMMA/PVAc film was better than that of CNT/PMMA/PVAc film. The electrical percolation thresholds were at 5 wt% and 2.5 wt% respectively in the CNT/PMMA/PVAc film and GCNT/PMMA/PVAc film. The volume electric resistivities of CNT/PMMA/PVAc and GCNT/PMMA/PVAc composite film are at 0.044Ω.m and 0.007Ω.m respectively at 15 wt% carbon nanotube. The significant difference of resistivity for the both types of composite film was due to different structure and crystaUinity of CNT and GCNT. Compatible blends of PMMA and PVAC would be a good candidate to produce a series of electrically conducting carbon nanotubes composites whose resistance is sensitive to the nature and concentration of an analyte in the vapor phase.