Study Of A Kind Of MWNTs/Silicone Rubber Composite Materials With Flexibility And Stretchability

In this paper, Multi-wall carbon nanotubes (MWNTs)/silicone rubber composite materials were prepared by the method of solution mixing with ultrasonic dispersion; then the MWNTs were pured by nitric acid, and chemically modified by 3-Aminopropyl-triethoxysilane (KH-550) or 3-(Trimethoxysilyl)propyl methacrylate (KH-570); at last the MWNTs which have been successfully modified by silane coupling agents were used to prepare the composite materials with the same method. The MWNTs were characterized by transmission electron microscopy (TEM), raman spectroscopy (Raman), thermal gravimetric analysis (TG) and fourier transform infrared spectroscopy (FT-IR). The mechanical and electrical properties of composite materials affected by the different MWNTs were also studied with the emphasis on their electrical properties affected by the stetching cycles when the materials were stetched 50%.The results showed that:the conductivity of composite materials which contain the pure MWNTs were not good, in contrast, BE-MWNTs have better enhancement for the conductivity of silicone rubber. The impurity particles in BE-MWNTs could be removed by purification of nitric acid, carboxyl, hydroxyl and the other oxygen-containing groups were brought to the surface of BE-MWNTs; the two silane coupling agents could be successfully grafted on the surface of the pured MWNTs, and the basic structure of MWNTs would not be destroyed by the oxidation of nitric acid. When the amount of MWNTs were in a certain range, the tensile strength of composite materials were significantly improved with the increasing amount of MWNTs, but the elongation at break of composite materials have a certain degree of reduction; compared with the pure silicone rubber, the conductivity of composite materials were improved with the increasing amount of MWNTs in the context of a certain mechanical properties. Especially, the composite materials still have conductivity after a certain number of stretching cycles, and the electrical conductivity had even been enhanced than before.Compared with the unmodified MWNTs, the composite materials which contained MWNTs modified by silane coupling agents especially by KH-570 had more excellent comprehensive performanc. It had shown that the residues of KH-570 on the surface of modified MWNTs could be combined with the curing agents in silicone rubber though covalent bonds, as a result, the interface force between matrix and MWNTs could be significantly improved, and the dispersion of MWNTs in the matrix may also be improved, thus the overall performance of composites could acquire significantly enhancement. When the addition level of KH-570-MWNTs was 5 wt%, the composites had the tensile strength of 3.23 Mpa, the elongation at break of 276.2%, the static conductivity of 37.716 mS/cm. The most importance was that the composite could maintain good electrical properties after 500 stretching cycles.