Introduction of Silicone Resin (III)


The condensation of methyl phenyl silicone resin was catalyzed by special catalysts. The selective catalytic properties of nucleophilic reaction led to the preferential activation of the phenyl substitution position in the molecular chain of methyl phenyl silicone alcohol, which led to the condensation of the silicone hydroxyl group at the phenyl substitution position prior to the methyl substitution position to form methyl phenyl silicone. The polymer chain of the resin retains part of the methyl substituted silicone hydroxyl group in the polymer. In the curing process of silicone resin, the reaction activity of methyl substituted silicone hydroxyl is obviously higher than that of phenyl corresponding silicone hydroxyl, thus obtaining methyl phenyl silicone resin with high reaction activity. The silicone hydroxyl group retained in the silicone resin polymer with large proportion, low steric resistance and high reactive methyl substitution position improves the adhesion of the cured silicone resin to the substrate.






Another function of special catalysts is to catalyze the ring opening reaction of polycondensation process. Inert organosilicon macrocycles and cage polymers formed during the hydrolysis of organochlorosilicon also participate in polycondensation by ring opening under the action of specific catalysts, eliminating inert macrocycles and cage polymers, thus completely solving the fundamental defects of easy re-adhesion after curing of thermocondensable silicone resin; at the same time, special catalysts promote inertia. Sex ring oligomers or cage oligomers participate in the polymerization, which is also conducive to the precise control of the composition of silicone resin and the improvement of product yield.






The above selective catalysts have strong catalytic activity, fast catalytic condensation reaction speed and high curing activity of the silicone resin obtained by condensation reaction. In order to ensure that the synthesis reaction proceeds smoothly and the curing activity and storage stability of the silicone resin are taken into account, the production of high curing active silicone resin should be carried out at relatively low heating temperature. In order to control the condensation reaction process, effective monitoring methods must be matched. Three methods for monitoring the end point of the condensation reaction of silicone resin and evaluating the properties of silicone resin were determined: 1) to evaluate the degree of condensation reaction by measuring the amount of water released in the process of the condensation reaction of silicone alcohol; 2) to determine the molecular weight growth of polymers by measuring the relative viscosity of materials in the process of the reaction; 3) to determine the molecular weight growth of polymers by measuring the content of water released in the process of the condensation reaction The gelation time was used to evaluate the curing properties of silicone resin.






By applying the above improved process, energy consumption is saved and product yield is increased. The prepared methyl phenyl silicone resin can completely overcome the serious shortcomings of low curing activity, poor adhesion and easy re-adhesion of methyl phenyl silicone resin after curing, besides retaining the excellent properties of high and low temperature resistance, climate aging resistance and high insulation strength of the silicone resin. The highly curable active organosilicon resin synthesized by nucleophilic reaction can not only be crosslinked and cured at lower temperature, but also the cured silicone resin film adheres firmly to various substrates. The cured film never returns to adhesion. The measured breakdown strength reaches 116 MV/m. After 24 hours of moisture exposure, the breakdown strength is still as high as 99 MV/m, and it remains 59M at 200 C. High breakdown strength of V/m. High curing active methyl phenyl silicone resin has excellent bonding properties. The author used highly curable active silicon resin to coat single crystal silicon specimens. After curing, the silicon resin was firmly bonded to the single crystal silicon specimens. Then the single crystal silicon specimens coated with silicon resin film were tested for cold and hot shock. The specimens were heated for 30 minutes in a 150 temperature oven, and then the freezing brine immediately put into - 40 temperature was taken out, and the thermal shock was repeated five times. Four of the five test specimens were bonded stably to monocrystalline silicon, while the other one was peeled off, but the peeled interface was in the inner layer of monocrystalline silicon. A thin layer of monocrystalline silicon was still adhered to the peeled silicon film, which showed that the bonding strength was great.


From Silicone Innovation Institute