Study On Preparation And Properties Of Modified Silicone High Temperature Resistant Coatings

Compared with other high temperature oxidation resistant methods,high temperature resistant coatings are more convenient and cheaper to construct.They are widely used in steel chimneys,high temperature pipelines,high temperature furmaces and military equipment.Silicone resin is widely used in the field of high temperature resistance because of its excellent high temperature resistance.However,Pure silicone resin itself has some shortcomings,such as long curing time,poor adhesion of paint film,and brittle paint film,which limit its use.The coatings prepared by epoxy modified organosilicon resin have excellent mechanical properties and high temperature resistance.Adding high temperature resistant pigments and fillers to the coatings can further improve the heat resistance of the coatings.The secondary film forming process of heat-resistant coatings and the changes of their protective properties after high temperature are studied,which are the research focus of heat-resistant coatings.Three monomers,CH3Si(OC2H5)3,(CH3)2Si(OC2H5)2 and C6H5Si(OC2H5)3,were used as raw materials in the experiment.Under the condition of concentrated hydrochloric acid as catalyst,silanol was hydrolyzed to form silanol,which was further condensated and copolymerized to form organosilicon intermediates with a certain degree of polymerization.Through single factor experiment,the formula and process of synthesizing prepolymer were optimized,including the effects of water addition,reaction temperature,catalyst addition and reaction time.Finally,the optimum synthesis conditions of silicone intermediates were determined as follows:water content 70%,reaction temperature 70oC,catalyst dosage 0.4%,the reaction time was 3 h.The organosilicon prepolymer prepared under these conditions has a viscosity of 150 cps and ethoxy content of 4.65%,which can be placed at room temperature for 30 days without stratification and gelation.The epoxy modified organic silicone resin was prepared with epoxy E-44 resin.The heat resistance of the resin was used as the main evaluation method,and the performance of the paint film prepared with the resin was tested.The specific method is to cross-link the prepared silicone intermediate with epoxy resin at high temperature,in which dibutyltin dilaurate is used as catalyst.According to the results of single factor experiment optimization,four factors and three levels were selected for orthogonal experiment design.The results of orthogonal experiments are as follows:the mass ratio of E-44 resin to silicone intermediate is 1:1,the reaction temperature is controlled at 160-170?,the amount of catalyst is 1.0%,the dosage of curing agent is 10%of that of resin and the ratio of phenyl to methyl in monomer is 0.3.The modified resin has the best performance.Under the optimum formulation,the modified resin is a transparent liquid with light yellow color,and the solid content of the resin is 65%.The resin is analyzed by infrared spectroscopy.The paint film prepared with this resin has good hardness and adhesion.Its heat resistance temperature can reach 300°C.The comprehensive performance meets the application standard of high temperature resistant paint film.The formulation and preparation process of epoxy modified organosilicon high temperature resistant coatings were optimized by discussing the influence of various factors.The performance of the coatings was tested.The conversion process of paint film was deduced by the thermal weight loss rate of the paint at 300-600? and the change of chemical resistance of the paint film at this temperature range.Furthermore,the correctness of the inference was verified by combining the infrared spectra of coatings and resins,indicating that an inorganic heat-resistant coating was formed at 6000C.Finally,the grinding time of pigments and fillers is 50 min,the dispersing time of paint is 60 min,the thickness of paint film is 200 um,the curing temperature of paint film is 80?,the ratio of pigments to base is 3.5,the dosage of curing agent is 15%,and the ratio of SiO2:Al2O3 is 3:1,the heat resistance temperature of the prepared paint can reach 600?,and the comprehensive performance meets the application requirements of“Determination of heat resistance of paints and varnishes”(GB1735-2009).