Surface Treatment of Nano Silica with Epoxy Silane Coupling Agent for Improving its Properties in Polyurethane Matrix

In this work, nano silica was modified by Glycidoxy propyl trimethoxy silane at different pH conditions. In order to study the surface treated particles, some testes on particles and poly urethane clear coat containing nano particles were performed. To characterize the particles some tests such as pH, density, FT-IR, elemental analysis and zeta potential were performed.Also in order to study surface chemistry of treated particles, Turbidity of particle in two solvents with different solubility parameters was implemented. The results show that the pH of treating bath, highly affects on amount of grafting. Maximum grafting content was obtained at isoelectric point of silane (4.7) and above isoelectric point of silica (5-6). Grafting silane on silica Surface causes the density of particles decrease and the isoelectric point increases. Sample with higher grafting has better dispersion stability in solvents with higher hydrogen bonding parameter (δH) and lower polar parameter (δP).This phenoma is because of increasing hydrophobisity of treated particles and decrease of polarity. Inorder to quantify interaction of particles with poly urethane matrix, Tensile strength, DMTA and Buchhol Hardness, were performed. The results were representative chemical and physical interaction between treated particles and poly urethane matrix which is increase considerably mechanical properties of nano composite.