Synthesis And Applications Of Heat Resisting And Thermal Insulation Coatings Based On Methylphenyl Silane Resin

Because of the unique Si-O-Si skeleton structure of its main chain,the silicone resin with high thermal stability,good weatherability and excellent insulation properties is widely used in the aerospace field.With the advancement of science and technology and the development of the defense industry and other industries,the temperature and requirements of thermal shock resistance of the coating materials have become higher and higher.Therefore,the exploitation of heat-resistant and thermal insulation coatings with excellent comprehensive performance has become the main development direction.In this paper,in order to solve the low curing activity of methylphenyl-silicon resin at room temperature and the problem of easy-to-return adhesion after curing,we designed and synthesised methyl phenyl silicone resin with the high-curing activity and studied the affects of catalysts,R/Si?Ph/R?inorganic fillers and trisilanol phenyl polysilsesquioxaneon to the overall performance of the resin.The specific work is as follows.Firstly,for the problems of low activity of methylphenyl silicone resin at room temperature and easy to return to stickiness after curing,the paper choosed tetramethylammonium hydroxide,zinc naphthenate as catalysts and phenyltrichlorosilane,methyltrichlorosilane,dimethyldichlorosilane as raw materials to synthesis methyl phenyl silicone resin with the high-curing activity.High temperature resistance and mechanical properties of the silicone resins synthesized in different catalytic systems were compared.The effects of R/Si and Ph/R on the high temperature resistance and mechanical properties of methylphenyl silicone resin were discussed.The study found that:tetramethylammonium hydroxide as a catalyst can not only catalyze the condensation reaction of silanol,but also has a strong catalytic ring-opening function,it can catalyze the opening of the inert oligomers to involve in the reaction,as a result,the inert oligomers were eliminated and the product yield was improved.What's more the methylphenyl silicone resin can be cured at room temperature and it did not return to stickiness after curing,which can improve its practical application.The above-mentioned methylphenyl silicone resin was used as a resin matrix and a high-temperature resistant coating was prepared by compounding a kind of inorganic filler such as nano-silica,talcum powder,mica powder,low-melting glass powder,titanium dioxide,nano-silicon carbide,and other additives.A lot of the tests such as high-temperature resistance,adhesion,impact resistance,hardness,and thermal weight loss were carried out and the best formula for high temperature resistant coatings was found.It was methyl phenyl silicone 40 g,nano silica 0.4 g,mica powder 2.5 g,talcum powder 2 g,low melting point glass powder 5 g,titanium dioxide 6 g,nano silicon carbide 3 g.At this point the hardness of the coating was81HD and adhesion of the coating was 3.5 MPa.It can withstand 800°C.The surface and composition of the coating after curing and high temperature calcination was analyzed by Fourier Infrared Analyzer,X-ray Diffractometer,and TGA.It was found that the methylphenyl silicone itself had a lower temperature Excellent heat resistance property.At higher temperatures,the Si-O-Si bond of the main chain of the silicone resin breaked.As a result,SiO₂ and Si-O short chains had a stenting effect on the coating.The Al₂?SiO₄?O produced by the reaction between inorganic fillers had excellent high-temperature resistance and the molten Al?OH?₃ generated under high temperature environment can fill the coating cracks and keep the coating surface well.The methyl phenyl silicone resin was used as matrix and a thermal insulation coating was prepared by compounding a kind of filler such as hollow glass microspheres,sepiolite fibers,expanded perlite,expanded vermiculite,and diatomaceous earth.The effects of various fillers on the thermal insulation properties of the prepared thermal insulation coating were investigated respectively.The best formula for thermal insulation coatings:methyl phenyl silicone resin 40 g,hollow glass beads 2 g,expanded perlite 0.6 g,sepiolite powder 2 g,expanded vermiculite 3 g,diatomite 1.5 g.At this time,the coating had a thermal conductivity of 0.0856 W/?m·k?,a hardness of 82 HD,an adhesion of 3.2 MPa,and an impact resistance of50 cm.The quality loss was very low before 400°C.,and the thermal stability was reliable.The prepared thermal insulation coating had good heat insulation,heat resistance and mechanical strength.Finally,TriSilanolPhenyl-POSS was used to modify the methylphenyl silicone resin and the effect of the addition amount of TriSilanolPhenyl-POSS on the heat resistantance and mechanical properties of the composite was studied.Thermogravimetric analysis and other characterization methods proved that the addition of TriSilanolPhenyl-POSS can effectively inhibit the thermal degradation of methylphenyl silicone resin.The results show that the coating had the best heat resistance when the addition amount of TriSilanolPhenyl-POSS was5%.The initial decomposition temperature was 400°C and the weight loss rate was 2.5%at500°C.And the coating had a hardness of 92 HD and the adhesion of 3.2 MPa.It's impact resistance was 50 cm.