Study On The Structure And Properties Of Multi-walled Carbon Nanotubes/Epoxy Resin Composites

In this paper, it is mainly from dispersion and interface bonding point of view suggested that the multi-walled carbon nanotubes (MWNTs) were filled into polymer matrix. By characterization of the microstructure and mechanical properties of the MWNTs/polymer composites, the effect mechanism of MWNTs in the polymer matrix was analyzed.MWNTs were treated by acid, base and amino-functionalization. Fourier transformed infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and Raman spectroscopy were used to characterize the shape and structure of treated MWNTs. The result showed that, under mild reaction condition, acid solution (V_H2SO4/V_HNO3=3:1) could remove the impurities presented in the pristine MWNTs such as amorphous carbon and metal catalysts and produce carboxyl groups on the surface of MWNTs without great damage to the structure of MWNTs. The surface of the MWNTs treated by acid could graft triethylene-tetramine (TETA) groups successfully by amidation route. MWNTs treated by base solution (V_{H2O2/VNH4OH=1:1} could graft amido groups on the surface and had better dispersion and less damage to the structure than MWNTs treated by acid solution, but the metal catalysts could not be removed absolutely.MWNTs/epoxy resin composites were prepared using solution mixing method, mechanical properties test found that the flexural strength of the composites were lower than pure epoxy resin when the contents of MWNTs was 0.1 wt% loading. However, MWNTs presented reinforcement effect in the epoxy resin matrix when the contents was 0.5wt% loading. Because of homogeneous dispersion and excellent interface bonding, MWNTs treated by base had better reinforcement in the epoxy resin matrix than other MWNTs. Flexural strength of the composites was enhanced 26% with only 0.5wt% loading of MWNTs treated by base, and the glass transition temperature increased 19.5℃ Surfactant was in favor of the dispersion of MWNTs in the epoxy resin matrix, flexural strength of the composites had maximum with 1.5wt% loading of MWNTs dispersed by surfactant. But the reinforcement effect was not remarkable because of weak interface bonding between the MWNTs dispersed by surfactant and the epoxy resin matrix. Thermal properties test found that addition ofMWNTs had few effect on thermal stability of the epoxy resin matrix at high temperature.The high stability and high concentration MWNTs solution(5 mg/ml) was obtained by a ultrasonic dispersion method in the 1.0wt% sodium deoxycholate(DOC) aqueous solution. Then Mixing the MWNTs solution with Poly (vinyl alcohol)(PVA) aqueous solution, vaporizing the water, the MWNTs/PVA composites with highly homogeneous dispersion of MWNTs could be obtained. Tensile properties test found that the tensile modulus and tensile yield strength of the MWNTs/PVA composites film increased by 140% and 64.5% with 5.0wt% MWNTs dispersed by surfactant, respectively, comparing to the pure PVA film. Differential scanning calorimetry analysis (DSC) found that the crystallinity of MWNTs/PVA composites was lower than pure PVA. Therefore, mechanical properties enhancement of the MWNTs/PVA composites was not attributed to changes in crystallinity but to the highly homogeneous dispersion of MWNTs in the PVA matrix.