Research On High Properties Of Natural Rubber/Multi Walled Carbon Nanotube Composites

Multi-walled carbon nanotubes (MWCNTs) as a good reinforced material possess high strength, high flexibility, excellent electrical conductivity and thermal conductivity. However, MWCNTs are difficult to integrate with natural rubber (NR) matrix due to the high surface area and aggregation. Traditional approach to obtain NR composite is "dry mixing", however, this process not only consumes much more energy and contaminates the environment, but also does harm to the heath of manipulator. Therefore, in this paper a novel technique which is different from "dry mixing" was developed and vast studies have been done on "latex compounding" method. In addition, the method of grafting polymer on the surface of MWCNTs is complex and organic solvents can cause serious pollution. Therefore, how to simplify the process and get a good reinforcement need be solved.Self-assembly is one of the methods of preparing high performance NR composites, and it could avoid complicated procedure and make MWCNTs disperse well, thereby reinforcing NR composites. The process of self-assembly NR/MWCNT composites involves two assembly steps. NR was spontaneously cross-linked with MWCNTs through electrostatic force. The fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), thermal gravimetric analysis (TGA), tensile characterization, cross-linking density and Zeta-size test were performed to characterize the properties of MWCNTs and nanocomposites.The results show that untreated MWCNTs (U-MWCNTs) perform a strong aggregated and twisted form in NR matrix, while MWCNTs modified by PDDA (MWCNTs-PDDA) assemble on the NRL particles as circles or disperse among NR particles. Moreover, U-MWCNTs perform a poor combine with NR matrix. When the MWCNTs-PDDA loading is less than 3 wt%, the interface between MWCNTs and NR seems very smooth.Due to the addition of inorganic MWCNTs, the glass transition temperature and storage modulus of nanocomposites are higher than pure NR, and rigidity of nanocomposites has been improved. Particularly, the tensile strength of nanocomposites is superior to pure prevulcanized NR when 2wt% MWCNTs-PDDA is loaded, peaking at 31.4MPa.MWCNTs possess special electronic property because of the lamellar structure and conjugative effect of MWCNTs. If MWCNTs form a channel in NR matrix through specific distribution, conductive rubber may be obtained, and it still need further study.We prepare NR/MWCNTs composite of high performance using a novel technique, "latex compounding", meanwhile the results in this paper reveal the mechanism between the micro structure and macro properties of NR nanocomposite, which lays the root for optimizing process conditions and developing industrial technique of intellectual property right for natural rubber reinforced by MWCNTs.