Carbon Nanotube / Polyacrylonitrile Composite Materials Research

Polyacrylonitrile (PAN) is the main raw material of carbon fiber with excellent performance, however, its mechanical properties is not ideal, and its electrical conductivity is extremely low, equivalent to an insulator. Carbon nanotubes (CNTs) have special mechanical properties and excellent electrical properties, which make them the ideal modification agent of polymer. This research is to add CNTs to the PAN matrix in order to improve the mechanical properties and electrical properties of composites.Multi-walled carbon nanotubes (MWNTs) were treated by mixed-acid, and then the best acidification time are decided. The morphology and chemical structure of the MWNTs treated via acidification are characterized by FT-IR, XRD and SEM. The results show that the mixed acid can effectively remove impurities in the raw MWNTs and polar functional groups such as-COOH and-OH etc are introduced on the surface of the carbon nanotubes. It has been examined that the MWNTs treated can be equably dispersed in the polar solvent N, N-dimethylformamide (DMF) medium for a long period.PAN powders was prepared via aqueous suspension polymerization. MWNTs treated by mixed-acid are added to the PAN matrix to prepare composite films of MWNTs/PAN with different ratio values by a solution of blending method. Testing methods, such as XRD, FT-IR, SEM, Megohmmeter, Tensile testing machine, DMA and other instruments are used to characterize the composite films. The results show that there are certain interfacial interactions between MWNTs and PAN matrix, in addition, MWNTs dispersed well in the matrix. The electrical properties and the mechanical performances of composite material are improved. When the content of MWNTs is 20 wt%, the performances become the best. The resistivities of the composite materials decrease with the increasing content of MWNTs. The percolation threshold of the composite material is 5-10 wt%. Comparing pure PAN materials with composite materials, the maximum tensile strength of composite materials is 1.63 times than the pure's, the elongation at break decrease 50 percent, and the resistivity decreased for almost 10 orders of magnitude. The storage modulus, loss modulus and glass transition temperature of composite materials increase with the increasing content of MWNTs gradually in a certain content scope.