Preparation And Performance Study Of Antistatic Composite With Functionalized Multi-walled Carbon Nanotubes

As a kind of carbon nano materials, MWCNTs has several excellent features, like high strength, high toughness, high conductivity, high thermal conductivity, exceptional thermal stability and so on. As filler,MWCNTs had been widely applied to the preparation of conductive,antistatic, thermal conductivity, mechanical enhancement and other various functional composite materials. But the huge surface energy and the high aspect ratio make MWCNTs easy to agglomerate and have bad dispersity in the resin matrix. The MWCNTs surface showed chemical inertness, which made MWCNTs difficult to form good interface structure with resin matrix. All this would limit the application of MWCNTs in the composite materials. Thus, the MWCNTs surface must be modified. In this thesis, MWCNTs surface was modified through adding functional feature and enhancing dispersibility, and then the modified MWCNTs was applied in the preparation of nanocomposite.1. Functionalized coating to MWCNTs: pyrrole reacted with the carboxyl of acid-treated MWCNTs and then MWCNTs grafted by pyrrole(MWCNTs-Py) was synthesized. Under the chemical oxidation of silver nitrate, polypyrrole was prepared on the MWCNTs surface by in suit polymerization. And silver nanoparticles were concomitantly produced on the MWCNTs surface when the polyprrole coated the MWCNTs. At last,terephthalic acid doped in the repeat unit of PPy through reaction of carboxyl and pyrrole ring. And MWCNTs with silver nanoparticles decorated, polypyrrole coated and terephthalic acid doped(MWCNTs@Ag-PPy@COOH) was prepared. The surface chemical structures of MWCNTs@Ag-PPy@COOH were characterized by FTIR,Raman, EDS, XPS, TGA and TEM. Then, the antistatic and thermally conductive nanocomposites were prepared by MWCNTs@Ag-PPy@COOH and epoxy. Interfacial structure between MWCNTs and epoxy resin was characterized by FTIR, DSC and SEM.The dispersibility of MWCNTs in the epoxy resin was characterized by TEM and AFM. The final result shows that good chemical interface structure generated between MWCNTs@Ag-PPy@COOH and epoxy resin. Besides, silver nanoparticles and polypyrrole enhanced the conductive and heat-conducting capabilities of MWCNTs in the resin matrix. And the dispersibility of MWCNTs in epoxy matrix was improved after terephthalic acid doping. The surface resistivity of nanocomposite was decreased to 1.3×108? at 0.5 wt% concentration of MWCNTs@Ag-PPy@COOH, and the thermal conductivity was increased by more than 170% compared to neat epoxy resin at 10 wt%concentration of MWCNTs@Ag-PPy@COOH.2. Improving the dispersibility of MWCNTs: Polypropylene acyl chloride was got by free radical polymerization. Next, acyl chloride group reacted with the azide group and H20 in the aqueous solution of sodium azide, and the azide polyacrylic acid was prepared. The azide group was decomposed into nitrene structure and the nitrene struction took place cycloaddition reaction with the carbon of MWCNTs surface, which made polyacrylic acid modify to the MWCNTs surface. At last, the MWCNTs modified by melamine (MA-APAA-MWCNTs) was prepared through the reaction of melamine and carboxyl. The surface chemical structures of MA-APAA-MWCNTs were characterized by FTIR, Raman, EDS, TGA,and TEM. Then, MWCNTs, melamine, paraformaldehyde and other promoter were composited to prepared MWCNTs/melamine resin composite materials. Interfacial structure between MWCNTs and melamine resin foam was characterized by FTIR, DSC and SEM. The final result shows that MA-APAA-MWCNTs was beneficial to improve the dispersibility of MWCNTs in the foam matrix. And good interface structure generated between MA-APAA-MWCNTs and melamine resin foam. The foam composite materials could meet the requirement of antistatic at 6 wt% concentration of MA-APAA-MWCNTs.