Research On Modification Of Ceramic Nanopowder And Its Rubber Nanocomposites

Using nanomaterials with excellent performance to develop special and functional new rubber nanocomposite materials has become an important research direction in the field of rubber. But the nanoparticles are more difficult to disperse homogenously in the rubber matrix than the thermoplastics due to their high specific surface area and high surface free energy. So the research of rubber nanocomposites is focused on nanomaterials' surface modification, nanomaterials' dispersion in the rubber matrix, the strengthening mechanism of nanomaterials and the relationship between structures and properties of rubber nanocomposites, etc.This paper aims at three categories of automotive rubber products (oil seal of rubber shock absorbers, wear-resistant rubber hoses and rubber stopper). Surface modification of ceramic nano-materials and the preparation and performance of the rubber nanocomposites are in deep investigation. The work could be summarized as follows:1. The nano-sized amorphous silicon nitride and hexagonal aluminum nitride which are produced by Hefei Kaier Nanotechonlogy Development Co., Ltd. were chose as the research object and this two ceramic nanopowder's surface structure were studied. FTIR and XPS analysis were used to compare the oxidation and hydrolysis reaction of nano-silicon nitride, micro-silicon nitride and nano-aluminum nitride when open in the humid air for a certain time. of the situation. The present study may laid the foundation for a further investigation of ceramic nanopowder's surface modification.2. Three coupling agent which could be used for surface modification of nano-Si₃N₄ and nano-AlN were designed and synthesized for different rubber /ceramic nanocomposite system to enhance homogenous dispersion and compatibility between nanoparticles and rubber matrix. Macromolecular coupling agent MAA-BA-AN tercopolymer and MMA-BA-VTES tercopolymer were both synthesized by free radical solution copolymerization method. The impact of initiator and transfer agent's concentration on the tercopolymer's molecular weight were discussed. Nano-zinc methacrylate was synthesized at room temperature through chemical deposit method. The factors influencing the size and structure of nano-ZDMA such as stir rate, dropping rate, solution concentration were studied in detail. The structure and morphology of nano-ZDMA were characterized by FTIR, NMR, GPC, DSC and TGA.3. The nano-ceramic powders were modified with the coupling agent mention above. The silicon nitride nanoparticles were modified with MAA-BA-AN tercopolymer and MMA-BA-VTES tercopolymer, the aluminum nitride nanoparticles were modified with MMA-BA-VTES tercopolymer, the zinc methacrylate nanopowder were modified with direct coating method and in-situ graft polymerization method respectively. The result of surface modification were characterized by FTIR, XPS, TGA, TEM, SEM, nano-size analysis, the settlement test and contact angle determination.4. Design and fabricate a thermal fogging nanopowder's surface modification equipment, intermittent surface modification machine, which can be applied in industrial production. The macromolecular coupling agent solution can form sub-micron droplet with this machine, then well-mixed with nano-powder which suspended in mixing chamber, thus the coating efficiency is enhanced and the modified nanopowder could achieving homogenous dispersion in the rubber matrix.5. The influences of different mixing process on nanoparticles' dispersion in the rubber matrix were discussed. The two-step internal mixing process was confirmed as the effective mixing process to achieving homogenous dispersion in the rubber matrix based on Carbon Black Dispersion Analyzer, Rubber Processing Analyzer and TEM.6. Three kinds of rubber/ ceramic nanocomposites are designed and prepared by two internal mixing process, which are as follows: nano-silicon nitride modified with tercopolymer MAA-BA-AN/ NBR nanocomposite; nano-aluminum nitride modified with tercopolymer MMA-BA-VTES / NR/SBR nanocomposite; nano-silicon nitride modified with nano-zinc methacrylate in situ graft polymerization / EPDM nanocomposite. The optimal loading of ceramic nanopowder was determined based on the results of nanocomposites' mechanical properties, oil resistance, wear resistance and anti-aging properties. The relationship between structure and properties of rubber ceramic nanocomposite was studied.7. Nano-silicon nitride modified with tercopolymer MAA-BA-AN / NBR nanocomposite is used to produce oil seal of automobile shock absorber; nano-silicon nitride modified with nano-zinc methacrylate in situ graft polymerization / EPDM nanocomposite is used to produce wear-resistant hose, nano-aluminum nitride modified with tercopolymer MMA-BA-VTES / NR/SBR nanocomposite is used to produce rubber stopper. The results of life test showed that these three products all reached the international advanced level.To sum up, the ceramic nanopowder(nano-silicon nitride and nano-aluminum nitride ) were applied to the preparation of rubber nanocomposites creatively. Novel macromolecular coupling agents for ceramic nanopowder were designed and synthesized according to different rubber nanocomposite systems. The uniform dispersion of nanopowders in the rubber matrix was realized successfully.The results confirmed that nano-silicon nitride and nano-aluminum nitride can not only enhance the strength and toughness of the rubber, but also improve other properties, such as oil-resistance, wear-resistance properties. Moreover, a thermal fogging nanopowder's surface modification equipment, intermittent surface modification machine was designed and fabricated for the first time. All these works above explore a successful road for breakthrough the technological bottlenecks of nanoparticles' dispersion in rubber.