Types and properties of silicone resins

Types and properties of silicone resin Silicone resin can be basically divided into three categories: polyalkyl silicone resin, polyaryl silicone resin and polyalkyl aryl silicone resin according to the different organic substituents of silicon atoms in the silicon oxygen chain link .

Polyalkyl organosilicone resin

Polymethyl silicone resin

Polymethyl silicone resin is generally composed of siO3/2, CH3SiO3/2, (CH3) 3sio2/2, (CH)SiO1/2 and other siloxane chain copolymers.Each silicon atom is only connected with the following two methyl raw materials (such as methyl trichlorosilane, dimethyl dichlorosilane), can be prepared network structure of poly methyl silicone resin, heating can be transformed into insoluble infusion products.Polymethyl silicone resin has high heat resistance and oxidation resistance.The flake samples made of methyl silicone resin will not be damaged when heated to 550℃ in vacuum or heated to 500℃ in hydrogen flow, and will not be fused in a long time.The mica pressed sheet hardly produces smoke when heated to 600 ~ 700℃.The resin plastic sheet was heated at 200℃ for a year without causing damage. When the temperature exceeded 300℃, its surface was slowly oxidized by oxygen in the air.Beyond the maximum operating temperature, the resin does not crack into carbon and its surface is oxidized to silicic anhydride.Resin also has very high electrical properties, it is not sensitive to water, boiling water at 100℃ for 30 min after little change in properties.

Polyethyl silicone resin

Polyethyl silicone resins are copolymers containing ethyl groups in siloxane chains.The polymerization rate of polyethyl silicone resin is slower than that of polyethyl silicone resin, but the ethyl group connected to the silicon atoms in the siloxane chain can increase the solubility of the resin and reduce its hardness.In order to prepare the insoluble and insoluble polyethyl silicone resin, the best ratio of the ethyl base to the number of silicon atoms is 0.5~1.5.When this value is lower than 0.5, the resin polymerization is too fast, and a large amount of water is produced in the condensation process, so that the resin becomes brittle and not firm, and it is easy to crack at high temperature;When the value is 0.5~1, the flexibility and elasticity of the condensation product are increased, when the value is about 1, the product formed has good elasticity, 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 increases and it is difficult to condense into solid.The condensation product with a value of 2 is typically elastomer.Polyethyl silicone resins are more easily intermixed and copolymerized with polyesters, polyacetals and other organic polymers than polymethyl silicone resins.

Polyaryl silicone resin

Polyaryl silicone resin is a copolymer containing only phenyl in siloxane chain, with high heat resistance, strong oxidation resistance and other excellent properties.The polyaryl silicone plastic sheet is heated in the air to 400℃ or 500℃, after a few hours of phenyl will not fall off from the silicon;In 400℃ heating for a longer time or put the polymer in the sealed tube with dilute acid or bromine water, the phenyl can be detached.Using three functional groups of organic silicon monomer (phenyl trichlorosilane), after hydrolysis rearrangement to form a trapezoidal polymer - total phenyl silicone resin has higher heat resistance than the general resin.

Polyalkyl aryl silicone resin

Poly alkyl organic silicone resin and poly aryl organic silicone resin two kinds of resin properties can be added in one kind of resin another kind of resin to change, the formation of poly alkyl aryl organic silicone resin.In fact, it is not simply mixed, but synthesized by directly connecting alkyl and aryl groups to the same silicon atom, or by hydrolysis and condensation of alkyl and aryl chlorosilane to form copolymers.Polyalkyl aryl silicone resins have better mechanical properties and hardness than pure alkyl or aryl silicone resins.