A Study On The Preparation And Properties Of Carbon Nanotube/Polyvinyl Alcohol Composite Film

Carbon nanotube (CNT) is considered as an ideal reinforcement for polymer materials for excellent mechanical, electrical and thermal properties. However, it is quite difficult to disperse CNTs with a high volume fraction into the polymer matrix uniformly. As a result, the mechanical property is far below those expected. The preparation of CNT macroscopic material (CNT fiber or film)/polymer composites is one of the effective ways to obtain high performance CNT based composites. To date, CNT/polyvinyl alcohol (PVA) composite films could be drawn from CNT arrays in one step. However, the number of layers and length of composite films could not be controlled and continuous production is still a big challenge. On the other hand, CNT based composites spun from CNT aerogels cannot be fabricated in one step as an enclosed experimental environment is involved.In this thesis, CNT/PVA composite films are prepared by in situ deposition of CNT hollow cylinders in the atmospheric environment. A paper tape process and a rotating drum process are adopted to prepare composite films with good mechanical and electrical properties. The collecting rate has a great effect on the property of composite films. The tensile strength and modulus of films are improved at a faster collecting rate due to the good alignment of CNTs in the films.With the infiltration of PVA solution of a proper concentration (0.05 wt.%), the bonding of CNTs with PVA could increase the tensile load and decrease the film thickness. As a result, the tensile strength and electrical conductivity of composite films with 60 wt.% CNT prepared by the paper tape process reach 1.7 GPa and 804 S cm-1, respectively. This strength is one order of magnitude higher than those of the initial CNT and PVA films. Not only the number of layers and length of the films are controllable in this process, but also the high performance CNT composite films can be prepared continuously. The tensile strength and electrical conductivity of composite films with 62 wt.% CNT prepared by the rotating drum process reach 2.9 GPa and 1058 S cm-1, respectively. The strength is 3.2 times higher than that of the pure CNT film, and the strongest among the CNT/PVA composites reported to date. The rotating drum process is a simple operation and suitable to prepare CNT- based composites with high strength and electrical conductivity. High volume fraction, good alignment of CNTs and the strong interfacial bonding between CNT and PVA could be achieved in both of the two approaches studied. This paves a new way to prepare high performance CNT-based composites.