Surface Modification Of Nanoparticles And The Solvent Effect In This Process

Silicon nitride (Si3N4) is a high-performance ceramic material. Now, nano-Si3N4 has been applied widely because of its high thermal stability, high hardness, low friction coefficient and chemical resistance. But nano-Si3N4 is easily agglomerate, due to its high specific surface area and high surface free energy, which will cause the nano-Si3N4 not to be dispersed homogenously in the rubber matrix. So the excellent properties of nano powder can not exhibit adequately in rubber/nano-Si3N4 composites. The researcher of rubber nanocomposites 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 solvent effect in modification.1. In this paper, one new macromolecule HFMA-MMA-VTMS coupling agent was designed and synthesized for fluorubber/nano-Si3N4 composites system to enhance homogenous dispersion and compatibility between nano-Si3N4 and FKM matrix. The structure, properties and number-average molecular weight of HFMA-MMA-VTMS were systematically investigated by FTIR, NMR, VPO, GPC and TGA. Nano-Si3N4 powder was modified by macromolecular surface coupling agent (HFMA-MMA-VTMS). FT-IR and TGA indicated that HFMA-MMA-VTMS bonded covalently on the surface of Si3N4 nanoparticles, and an organic coating layer was formed. Size distributions analyzer and TEM revealed that modified nano-Si3N4 has good dispersibility in chloroform.2. The solvent effects of surface modification of nano-silica by KH570 silane coupling agent in different solvents were discussed. Nano-silica powders after modification was characterized by FTIR, nano-particle size analyzer, TGA, surface elemental analysis and contact angle. We observe the dispersion of modified powders in different solvent, and found that the KH570 has little effect in modification of nano-silica, and has effect in re-dispersion of nano-silica.3. The solvent effects of surface modification of nano-powders with different surface modifiers LMPB-GMA and LMPB-KH570 in different solvents, such as n-heptane, ethyl acetate, DMF, were discussed. Silicon nitride powders after modification were characterized by TGA, sedimentation experiments, TEM and other methods. The results show that the polarity of solvents can effect the modification of nano-Si3N4. The modification of nano-Si3N4 in medium polarity solvent was the best. The mechanism of modification of nano-Si3N4 in different solvent was discussed in this paper.