| Rubber Nanocomposites is new type of polymeric composite in which one component has the dimension less than 100nm at least, and it is one of the focuses on which intensively studies in the field of materials. Silicon nitride (Si3N4) is a high-performance engineering ceramic material. Recently, silicon nitride ceramics has been applied widely because it has moderate density, high hardness and elastic modulus. In addition, it has high thermal stability, chemical resistance and good electrical insulation. But nano-Si3N4 is easily agglomerate; the reason is that nano-Si3N4 has much surface area and high surface activity. All of these will cause the nano-Si3N4 powder to be dispersed difficultly. So the excellent properties of nano-powder/rubber composite materials can not exhibit adequately. This work focused on synthesization of macromolecule surface coupling agent, surface modification of nano-Si3N4 powder, dispersion of nano-Si3N4 powder in the rubber matrix, and the complex properties of rubber nanocomposites.1. Low molecular weight liquid polybutadiene-y-methacryloxypropyl trimethoxy silane (LMPB-g-KH570) were synthesized by solution polymerization. The structure of LMPB-g-KH570 was investigated by FT-IR,1H-NMR, TGA, DSC et al. The results indicated that the KH570 were respectively grafted onto LMPB. The graft ratio of LMPB-g-KH570 was from 27.13% to 35.07%(wt%). The results of TGA and DSC show that LMPB-g-KH570 graft copolymer had good thermal stability. Its average molecular weight was measured by VPO. The Mn value of LMPB-g-KH570 was calculated as 4025, meeting the requirement that optimum number-averaged molecular weight should be in the range of 3000-10000.2. Nano-Si3N4 was modified macromolecular coupling agents LMPB-g-KH570. The properities of modified nano-Si3N4 and raw nano-Si3N4 were characterized by FT-IR, TGA, TEM et al. FT-IR, TGA and DSC indicated that LMPB-g-KH570 bonded covalently on the surface of Si3N4 nanoparticles, and an organic coating layer was formed. The reaction condition was optimized by the dispersion stabilization. TEM revealed that modified nano-Si3N4 possessed good dispersibility in ethyl acetate and the diameter was about 100nm. TGA also indicated that the using efficiency of LMPB-g-KH570 was 63.67%, and chemical using efficiency reach 30.66%. Contact angle and surface free energy investigated that the hydrophile was weakened and the hydrophobicity was enhanced. After modification with graft copolymer (LMPB-g-KH570), the surface free energy of nano-Si3N4 decreased sharply from 112.32 to 70.12 J/M2.3. Nano-Si3N4/acrylate rubber (ACM) composite were prepared by blending techniques, the microstructure of nanocomposites were analyzed and discussed by RPA-8000, SEM and TEM. The results showed that modified nano-Si3N4 effectively improved the micro-interface interaction of nanocomposite and the performance of vulcanized and mechanical properties of the ACM. The results show that in the RPA dynamic mechanics performance scanning test on the raw rubber andmixed performance test, modulus of elasticity G' and loss fact or tanδalong with frequency and strain elevating, separately demonstrated reduces and increases, enhance the frequency and strain suitable may improve its workability. Compared with pure ACM, the curing time of ACM nanocomposites reduced 38 seconds, the tensile strength increased 24.8%, tear strength increased 3.39%. |
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