Study And Preparation Of Polymer/Nano-Si₃N₄ Composites

Polymer nanocomposites are new type of polymeric composites in which one component has the dimension less than 100 nanometer at least. Polymer nanocomposires not only maintain the excellent performances of the polymer matrix, but also give full play to nanotechnology, restrain the oxidation and accumulation of nanoparticles to keep higher long-term stability of the system. So in recent years the field attracts more and more researchers. In this paper, we carried out a series of research on the polymer/nano- Si₃N₄ composites:1. The surface modification of nano-Si₃N₄Nano-Si₃N₄ is treated by the modification agent of small molecule and characterized by FTIR, TGA, Surface contact angle test, etc. Si₃N₄'s dispersion stability in MMA is enhanced by modification of KH-845-4 and NDZ-102 can significantly increase the powder dispersion stability in toluene. Experiments show: surface modification belong to chemical modification; the surface of the powder is coated by a certain amout of modification agent; particle size decreases after modification.2. The study of polymerization process of MMA/nano-Si₃N₄ system and the analysis of dynamic mechanical property of the compositesPolymerization process of MMA/nano-Si₃N₄ was studied by DSC. Effects of polymerization temperature, nano-Si₃N₄ amount and initator concentration of AIBN on polymerization rate were investigated in this article. The results show that with the polymerization temperature rising, the rate of polymerization increased; the initiatior concentration could effectually improve the polymerization rate; but with the increasing of nano-Si₃N₄ amount, the polymerization rate was decreased. From the kinetic results, the rate of polymerization, Rp at 70℃was expressed by Rp=K[Si₃N₄]^-0.14[AIBN]^0.79[MMA]Composites dynamic mechanical analysis shows that with the system nano-powder content increasing, the system's Tanδ, storage modulus E′and loss modulus E″showed systematic changes. Tanδcurves show PMMA composite system's Tg is higher than pure PMMA, and with the increasing amount of powder, composite materials Tg first increase and then decrease; storage modulus first increase further decrease, composite system higher than pure system; loss modulus peak height of the first decrease and then increase.3. The Preparation and characterization of PPS/nano-Si₃N₄ compositePowder treated by the modification agent is filled into PPS. And the composites are characterized by tensile test, impact performance test and DMTA. The results show: (1) The appropriate amount of nanoparticles can better improve the tensile and impact properties, and composites dynamic mechanical properties regularly change. (2) From the contrast of composit systems filled by nano-Si₃N₄, micron Si₃N₄ or nano-Si₃N₄/GF, nano-system's tensile properties and impact properties are clearly better than the micron system, but lower than the nanoparticle/GF system.