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Classification of Silicone Resins-According To the Mechanism of Crosslinking Curing Reaction

Mar 16, 2023

According to the different curing methods of cross-linking, silicone resin can be divided into condensation type, lead catalytic addition type and peroxide (free radical type) curing type, which is the main curing mechanism of the currently industrialized silicone resin.

CD condensation type condensation reaction is the most common curing reaction mechanism that has been used for a long time. At present, most silicone resin varieties also use dehydration reaction or deethanol reaction, polymerization and crosslinking to form a network structure, and in particular, dehydrogenation reaction is also used, which is the main way of curing silicone resin. Although the new silica bond formed by condensation reaction can still play its original heat resistance, high strength, good adhesion and low cost. However, during curing, due to the formation of bubbles and pores in the cured resin layer and the volatilization of organic solvents when the low molecular gas of the by-product is released, the amount of functional groups is difficult to control, the storage stability is poor, and the adhesion and drying are difficult, so most of them are used as surface coatings, coil impregnating paint, laminates, hydrophobic agents, adhesives, etc.

The peroxide curing uses the silicone polymer containing double bonds and the peroxide as the curing initiator, which is another way to cure the silicone polymer. At this time, the decomposition temperature of the peroxide used determines the curing temperature of the resin. Therefore, when the resin is stored at low peroxide decomposition temperature, it has good stability. However, partial contact with air is necessary to prevent the product from curing during storage. It can be used for coil impregnating paint, adhesive, laminate, etc.

The curing mechanism of lead addition reaction addition molding silicone resin is to cross-link through the hydrosilylation addition reaction between SiO2 containing Si-Vi bond and SiO2 containing Si-H bond under the action of lead catalyst, so as to achieve the purpose of curing. The addition silicone resin exists in the form of liquid, does not use any organic solvent to dissolve, does not contain organic solvent, does not have low molecular matter, does not produce by-product gas, the curing conditions are mild, does not produce bubbles and sand holes when curing into film, does not affect the electrical performance, does not pollute and has large shrinkage and other shortcomings, so it can obtain high-quality cured products with accurate size, and has small internal deformation and excellent internal conductivity, thermal conductivity Corona resistance and thermal shock resistance. 

At the same time, because the number of reaction functional groups can be arbitrarily controlled, the crosslinking number can be preset, so the products from hard to soft can be obtained at will, and the reaction is easy to control. However, compared with condensation impregnating paint, its synthesis process is relatively complex and its cost is relatively high. It usually consists of basic resin, cross-linking agent, active diluent, lead complex catalyst and inhibitor. The catalyst is easy to be poisoned. When there are a small amount of various compounds in the system that can poison the catalyst (such as compounds containing amines, P, As, S, etc.), they will seriously hinder the curing. It is necessary to strictly control the poisons in raw materials and products, and avoid contacting with the substances or materials that poison the catalyst. Moreover, because the curing reaction results in the same siliceous base chain as the peroxide curing (SICH2CH III), the heat resistance is slightly poor. For example, solvent-free silicone resin can be mixed with foaming agent to produce anhydride to obtain foam silicone resin. Additive silicone resin is mainly used for bushing, coil impregnating paint, laminated plate, etc.

Among the three types of silicone resin, condensed silicone resin is the largest.

SILIBASE SILICONE currently including below silicone resins: Methylphenyl Silicone Resin Emulsion, Methylphenyl Silicone Resin Intermediate, Epoxy Modified Silicone Resin, Acrylic Modified Silicone Resin, Acrylic Modified Methylphenyl, Silicone Resin Emulsion, Epoxy modified methylphenyl Silicone Resin Emulsion, Smokeless, Silicone Resin, Self-drying Silicone Resin, Highly Active Silicone Resin, Methyl Silicone Resin Intermediate, Methyl MQ Silicone Resin, Vinyl MQ Silicone Resin, Silicone Adhesive.

If you have any problem about silicone resin,you can contact us. We are the professional factory of silicone resin in China.

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