Preparation Of Functional Nanosilica And Study Of Its Modification On Unsaturated Polyester Resin

Nanosilica, as the reinforced materials of polymers, is widely used in rubbers, plastics, adhesives,coatings and other fields. However, the high surface energy makes it difficult to disperse well in the polymers matrix thereby the nanometer characterizations of nanosilica cannot be played in the application.The conventional method of modification nanosilica is a modification of nano-aggregates, which is limited in the modifying effects because of its difficult to fundamentally solve the dispersibility of nanosilica. It would be opening up a new approach for the application of nanosilica in the polymer if we can obtain high dispersion of nanosilica by controlling the synthesis conditions of nanosilica.In this paper, we synthesized high dispersive nanosilica and reactive nanosilica by using sodium metasilicate as the silicon source, adopting the liquid phase in situ surface modification technology and controlling the parameters in the process of reaction. The reactive nanosilica was used as monomers to prepare a series of UPR/SiO2 hybrid materials, The reinforcing effect of nanosilica was investigated and the reaction mechanism between the polyester chains and the nano-silica was studied as well. The main research contents and results were as follows:1. The preparation of high dispersive nanosilicaHigh dispersive nanosilica is prepared by in situ surface-modification technology, and the optimal synthesis conditions are as follows: sodium silicate at a modulus of 1, the dosage of modifier HMDS to SiO2 is molar ratio of 1: 5, the dosage of dispersant ethanol is 4% of the solution by mass, using the pH adjusting agent 3 as the acidifying agent, sodium silicate solution at a mass concentration of 12%, anionic surfactant A is 1% by the mass of SiO2.2. The preparation of reactive nanosilicaThe reactive nanosilica Si-E was prepared by using silane coupling agent KH560 as the modifying agent. On this basis, reactive nanosilica Si-H containing active hydroxyl groups and reactive nanosilica Si-C containing active carboxyl groups were prepared by grafting amino acetic acid and diethanolamine on the surface of Si-E,respectively.3. Characterization of surface functionalized silicaThe obtained nanosilica was characterized by TEM, IR, XRD, TG, and the results of performances analysis showed that the dispersive nanosilica and reactive nanosilica had good dispersibility in unsaturated polyester, small apparent density, high transmittance, larger oil absorption value and specific surface area,presented spherical structures and the average particle sizes of them were about 100 nm.4. The preparation of reactive SiO2/ UPR hybrid materialsThe reactive nanosilica was used as monomers to participated the synthesis of UPR, thus a series of UPR/SiO2 hybrid materials were prepared by in-situ polymerization. The structure analysis of the hybrid materials indicated that the reactive nanosilica participating in the polycondensation reaction of the UPR,and the performances analysis of the hybrid materials indicated that the viscosity, alkali resistance,mechanical properties of the hybrid materials had been significantly improved compared to the pure UPR.Wherein the UPR/Si-H hybrid materials had the best mechanical properties, the tensile strength and impact strength of UPR/Si-H hybrid material reached maximum, increased by 41.2% and 112% higher than pure resin,when the surface modifier of SiO2 in an amount of 1:5 and Si-H in the mass fraction of 1%.Furthermore, Si-E could significantly increase the viscosity and alkali resistance of the unsaturated polyester.5. The modification effects of nanosilica powder, filter cake and unmodified fumed nanosilica for UPR under the same conditions were compared, the results of performances analysis showed that the hybrid materials prepared by nanosilica filter cake had the best performances.