| Sol-gel method, as the most sophisticated methods to the preparation of organic-inorganichybrid materials, has lots of advantages such as process is simple and easy to control, the lowermolding temperature, homogeneous distribution etc. All of these advantages make this methodwell meet people's demands of high-performance, multi-functional, low-pollution for coating.Methyltriethoxysilane (MTES) is a popular material for sol-gel process, because of the industry'sexcellent performance like high quality, low price and mild reaction process. It can formpolysiloxane sol with Si-OH by hydrolysis under acidic conditions and the Si-OH continuegelatinize reaction. Finally, the sol forms solid gel with3D network structure.In order to prepare high performance coating that high temperature resistant, hydrophobic,high hardness, highly adhesive to meet the special occasion requirements, characteristicPolytetrafluoroethylene PTFE resin is selected as the organic phase to prepare organic-inorganichybrid coatings, by mixing with sol. In order to solve the problem of dispersion of PTFE resin andobtain the polyorganosiloxane-PTFE composite coating. PTFE concentrated dispersion emulsionis selected as mixing material and mix the polysiloxane and PTFE emulsion at the sol phase. Andthen, it is cured forming a film at the low-medium temperature through the condensation gelationprocess. Finally, excellent performance polyorganosiloxane/PTFE coating is obtained. Thespecific details of study are follows:(1)According to the chemical reactions of MTES, differential heat effects are emerged inprocess of hydrolysis and condensation. Infrared imaging measuring temperature methods isadopted to track the temperature of reaction system with different catalyst, on which basis HClproper catalyst is selected. Study on the MTES condensation gelation time at different pH andtemperatures, it turn out that pH=2.0and temperature=55?are the most suitable conditions.Based on the equilibrium reaction of Si-OH with OH-and particle size, determine the optimalreaction time is50min. According to the above optimized conditions, a high Si-OH content, good dispersion performance polysiloxane sol is prepared. And then a study is carried out on thekinematic viscosity and particle size of polysiloxane sol by using a rotational viscometer andnanometer particle size analyzer.(2) Preparing different proportions of polysiloxane sol and PTFE emulsions composite paints,the kinematic viscosity of composite paints is measured. Particle size analysis is used forpolysiloxane sol, PTFE and composite paints particle size and the result shows that thepolysiloxane sol particle is adsorbed on the face of PTFE latex particles. And the state ofdispersion of the composite paints is analyzed by SEM. The curing temperature of compositepaints and curing time are analyzed by means of DSC and FTIR of OH respectively and resultsturn out to be150?and90min. The surface microstructure of different proportions compositepaints are studied by means of SEM, it turn out that when PTFE emulsion content are20%,16.7%and14.3%the coating show smooth morphology surface and excellent film forming performance.(3) Prepare composite coating according to proposal proportions of polysiloxane sol andPTFE emulsions, and then using the composite paints prepare composite coatings, by the way ofspray-coating process and heat curing. The measure of FTIR is applied to analyze thechemical structure of composite coatings. The results show that the composite coating containingboth characteristic chemical structures of polysiloxane and PTFE. The surface morphology andinternal physical structure are analyzed through optical microscope and SEM. The results revealthat the surface shows the character of nano-morphology and internal physical structure shows themicro-nano composite structure. The surface roughness of composite coating is analyzed by AFM.The thickness of coating is measured by propeller micrometer and optical microscope. Theperformance of hydrophobic and oilphobic of composite coating is tested by contact angle ofwater and oil. The thermal performance of composite coating is tested by TG, the result reportsthat when the temperature is up to500?the mass loss is only18%and the heat resisitantperformance of composite coating is well. At last the comprehensive performance is testedaccording to the relevant standards and the outcome show all of the performance index of thecomposite coating meet or surpass the existing requirements of relevant coating. |
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