| The silicone resins are widely used in high temperature anti-corrosion coating, high temperature insulation coatings and high temperature fire retardant insulation coating. However, the problems such as low adherence to the substrate and the mechanical strength reduction of film at high temperature restrict its application. Therefore, modified the silicone resin with inorganic materials which have excellent heat resistance and insulation property was a new research direction in recent years.In this paper, octyl triethoxy silane, dimethyl triethoxy silane, phenyl triethoxy silane and boric acid were as raw materials to synthesize a series of flexible side chain octyl-dimethyl-boron silicone (BSR-1), rigid side chain phenyl-dimethyl-boron silicone (BSR-2), flexible and rigid side chains octyl-phenyl-dimethyl-boron silicone (BSR-3) by hydrolysis and poly-condensation reaction. The structures of above polymers were characterized by FTIR and NMR, and their heat resistance and corrosion resistance performances were tested and studied by TG and electrochemical workstation.Firstly, a series of flexible side chain BSR-1 were prepared with octyl triethoxy silane, dimethyl silane and boric acid. The influence of the monomer ratio, polymerization time to the properties of heat resistance mechanics, and rheology of BSR-1 were studied. The results indicate that the optimum R/Si ratio is 1.30. The number average molecular weight of the products desreased from 2939 to 2215 with the poly-condensation reaction time extended from lh to 3 h. But the heat resistance properties of the products were not affected remarkably with the poly-condensation reaction time. In mechanical performance test, the adhesion of BSR-1 poly-condensated for 1 h was 1 level, the impact force was 50 kg-cm-1, which behaves good mechanical properties. In rheological property test, the storage shear modulus and the shear loss modulus of BSR-1 increased with angular frequency increased in different poly-condensation time, while the rate of increase of the storage shear modulus were greater than the loss shear modulus. Also, the influencesof atmosphere and heating rate on the heat resistance were tested. The results showed that the residual mass of BSR-1 in air was greater than in N2. but the decomposed temperature of BSR-1 increased in N2 atmosphere. And the appropriate heating rate in N2 and air atmosphere was 10℃ -min-1Secondly, a series of rigid side chain BSR-2 were prepared with phenyl triethoxy silane, dimethyl diethoxy silane and boric acid. In the synthesis process, the appropriate dosage of water was about 60%. The thermal stability and the thermal mechanism of BSR-2 were studied. BSR-2 could withstand high temperature about 483 ℃. Thermal decomposition mechanism suggested that the thermal decomposition of boron silicone was divided into two stages, the first stage was thermal fracture and decomposition of the methyl side chain, phenyl group, hydroxyl group and other small molecules, the second stage was the fracture of a small amount of alkoxy that not hydrolyzed fully. Compared with BSR-1 prepared in the previous chapter, the mechanical properties of BSR-2 such as adhesion was 1 level, but its impact strength was 40 kg·cm-1Finally, a series of flexible and rigid alternated side chain BSR-3 were prepared with octyl triethoxy silane, phenyl triethoxy silane and dimethyl diethoxy silane and boric acid. Compared the properties of the aboved series silicone resins, the following results were obtained:(1) Heat resistance of silicone resin can be increased significantly after being doped with Boron element. The heat resistance temperature reached as high as 500℃; (2) Resins BSR-1, BSR-2 and BSR-3 showed good adhesion performance and reached 1 level; Impact resistance of BSR-1 and BSR-3 were better and reached 50 kg-cm-1, which indicate flexible side chain group octyl may be benefit for impact resistance. (3) The corrosion potential of BSR-3 was -6.480 V, the largest in three prepared series silicone resins, suggesting the boron doping and flexible and rigid alternated side chain benefit for increasing corrosion resistance performance. (4) In the anti-water, acid, alkali and salt water test, the resins do not blister and fall off after 30 days, the coating film of BSR-1, BSR-2 and BSR-3 behaved excellent corrosion resistance. |
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