The silicone resin can be basically classified into three types: polyalkyl silicone resin, polyaryl silicone resin and polyalkyl aryl silicone resin, depending on the organic substituent on the silicon atom in the silicon oxide chain.
Polyalkyl silicone resin
Polymethyl silicone resin
The polymethyl silicone resin is generally a copolymer composed of siloxane chains such as SiO3/2, CH3SiO3/2, (CH3)3SiO2/2, (CH)SiO1/2. A polymethyl silicone resin having a network structure can be obtained by using a raw material (for example, methyltrichlorosilane or dimethyldichlorosilane) having only two methyl groups attached to each silicon atom, and can be converted into a polymethyl silicone resin when heated. Insoluble and infusible products. Polymethyl silicone resin has high heat resistance and strong oxidation resistance. The methyl silicone resin is made into a sheet-like sample, heated at 550 ° C in a vacuum or heated to 500 ° C in a hydrogen stream, and is not damaged, and remains infusible for a long period of time; the prepared mica tablet is heated to There is almost no smoke at 600 to 700 °C. The resin plastic sheet was heated at 200 ° C for one year without causing damage. When the temperature exceeded 300 ° C, the surface was slowly oxidized by oxygen in the air. At temperatures above the maximum operating temperature, the resin does not crack into carbon and its surface is oxidized to silicic anhydride. The resin also has high electrical properties and is not sensitive to water. The performance does not change much after boiling in water at 100 ° C for 30 min.
Polyethyl silicone resin
Polyethyl silicone resin is a copolymer containing an ethyl group in a siloxane chain. Polyethyl silicone resins are slower to polymerize than polymethyl silicone resins, but ethyl groups attached to silicon atoms in the siloxane chain can increase the solubility of the resin and reduce its hardness. In order to obtain an insoluble and infusible polyethyl silicone resin, the ratio of the number of ethyl groups to the number of silicon atoms in the polymer is preferably from 0.5 to 1.5. When the value is less than 0.5, the resulting resin is polymerized too rapidly, and a large amount of water is generated during the condensation process, so that the resin becomes brittle and not strong, and is easily cracked at a high temperature; when the value is 0.5 to 1, the condensation product The flexibility and elasticity are increased. When the value is about 1, the formed product has good elasticity and can form a paint film with adhesion ability; when the value continues to increase to 1.5, the content of low molecular products in the polymer The increase is more difficult to shrink into a solid; when the value is 2, the condensation product is already a typical elastomer. Polyethyl silicone resin is easier to mix and copolymerize with polyester, polyacetal and other organic polymers than polymethyl silicone resin.
Polyaryl silicone resin
The polyaryl silicone resin is a copolymer containing only a phenyl group in the siloxane chain, and has excellent properties such as high heat resistance and strong oxidation resistance. The polyaryl silicone resin sheet is heated to 400 ° C or 500 ° C in air, and the phenyl group will not fall off from the silicon after several hours; it is heated at 400 ° C for a longer period of time or the polymer is placed in a sealed joint. The sealed tube is heated with dilute acid or bromine water, and the phenyl group can be detached. A trifunctional silicone monomer (phenyltrichlorosilane) is used to form a ladder polymer after hydrolysis rearrangement - all phenyl silicone resin has higher heat resistance than general resins.
Polyalkylaryl silicone resin
The properties of the two types of resins, polyalkyl silicone resin and polyaryl silicone resin, can be changed by adding another type of resin to one type of resin to form a polyalkylaryl silicone resin. In fact, it is not a simple mixing, but the alkyl group and the aryl group are directly bonded to the same silicon atom during the synthesis, or the copolymer is formed by hydrolysis and co-condensation of the alkyl group and the arylchlorosilane. Polyalkylaryl silicone resins have better mechanical properties and hardness than pure alkyl or aryl silicone resins.
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Zhejiang Runhe Organosilicone New Material Co.,Ltd(Factory)
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