A new method of grafting multi-walled carbon nanotubes on carbon fibers for improving the mechanical and thermal properties of woven fabric composites

Abstract

A new method of grafting multi-walled carbon nanotubes (MWCNTs) onto carbon fiber surface to improve the thermo-mechanical properties of woven carbon fabric reinforced composites was proposed. In this method, both carbon woven fabrics and MWCNTs were oxidized by sulfuric acid to generate carboxyl groups on their surfaces, respectively. Then silane coupling agent was used to react with the carboxyl groups to graft MWCNTs onto the carbon fiber surfaces of the woven fabric. The untreated, acid treated and MWCNTs grafted carbon woven fabrics were separately combined with polypropylene films to form composite plates by thermal-stamping. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were conducted to estimate the changes of element contents and functional groups on surfaces of carbon fibers and MWCNTs. Atomic force microscope was used to estimate the roughness of carbon fiber surfaces. Scanning electron microscopy, differential scanning calorimeter, dynamic mechanical thermal analysis and tensile tests were carried out to analyze the surface morphology, thermal, and mechanical properties of carbon fabrics and their composites. Testing results showed that MWCNTs could be successfully grafted onto the carbon fibers by using silane as an intermediate bridge. Compared with the untreated and acid treated composites, the in-plane shearing stiffness and fracture strength of the composites were increased significantly by MWCNTs grafting. In terms of thermal properties, acid treatment and MWCNTs grafting have little effect on melting point of composites. MWCNTs can promote the recrystallization process of the PP and reduce the numbers of imperfect crystals. As for thermo-mechanical properties, acid treatment deteriorated the bending storage modulus of the composite, while MWCNTs grafting could compensate it.