Silicone Overview

Silicone resin, scientific name polysiloxane resin; English name: Silicone resin.

Ingredient structure

Usually, various mixtures of methyltrichlorosilane, dimethyldichlorosilane, phenyltrichlorosilane, diphenyldichlorosilane or methylphenyldichlorosilane are used in the presence of an organic solvent such as toluene in the presence of It is decomposed by adding water at a lower temperature to obtain an acidic hydrolyzate. The initial product of hydrolysis is a mixture of cyclic, linear and cross-linked polymers, often also containing considerable hydroxyl groups. The hydrolyzate is washed with water to remove the acid, and the neutral initial polycondensate is thermally oxidized in the air or further polycondensed in the presence of a catalyst, and finally a highly cross-linked three-dimensional network structure is formed. Silicone resin is a thermosetting plastic and one of its most outstanding properties is its excellent thermo-oxidative stability. After heating at 250℃ for 24 hours, the weight loss of silicone resin is only 2~8%. Another outstanding property of silicone resin is its excellent electrical insulating properties, which can maintain its good insulating properties in a wide temperature and frequency range.






Silicone types mainly include


Methyl phenyl silicone resin, methyl silicone resin, low phenyl methyl silicone resin, silicone resin emulsion, self-drying silicone resin, high temperature silicone resin, epoxy modified silicone resin, silicone polyester Modified resin, self-drying environmentally friendly silicone resin, environmentally friendly silicone resin, non-stick coating silicone resin, high-gloss silicone resin, benzyl transparent silicone resin, methyl transparent silicone resin, mica adhesive silicone resin, Polymethyl silicone resin, amino silicone resin, fluorosilicone resin, silicone resin solution, silicone-epoxy resin, silicone polyester resin, solvent-resistant silicone resin, silicone resin adhesive, fluorosilicone resin silicone resin sealant , High temperature methyl silicone resin, self-drying silicone insulating paint, methyl MQ silicone resin, vinyl MQ silicone resin, silicone acrylic resin coating.




Apply:
The requirements for the mechanical properties of silicone resins mainly depend on the application. Silicone resins used as electrical insulating paints, coatings and adhesives, people are more concerned about its hardness, elasticity, thermoplasticity and adhesion. The hardness and elasticity of the silicone resin paint film can be varied in a wide range by adjusting the molecular structure of the resin. When the content of trifunctional or tetrafunctional chain units is higher, that is, the higher the crosslinking density, the paint film with high hardness and low elasticity can be obtained; the introduction of large sterically hindered substituents can improve flexibility and thermoelasticity, which is positive This is the reason why the flexibility and thermoplasticity of methyl phenyl silicone resin is better than that of methyl silicone resin. Therefore, the silicone resin does not need to use special plasticizers, but can meet the plasticity requirements by the appropriate combination of soft and hard silicone resins.


When used as some coatings, the hardness of the pure silicone resin coating film is insufficient, but the thermoplasticity is more than enough; if the organic modified silicone resin is used, it is easy to solve this contradiction.


Pigments and catalysts can also affect the hardness and elasticity of silicone resins. Pigments have the effect of accelerating the oxidation of the silicone paint film and converting it into a harder silica glass. Using low-activity catalysts, due to incomplete condensation reaction, only soft coatings can be obtained; on the contrary, using high-activity catalysts (such as compounds of Pb, Al, etc.), hard and brittle coatings can be obtained, but some catalysts (such as titanium acid ester) can effectively improve the hardness of the coating without seriously reducing the elasticity.


Silicone resin has good adhesion to iron, aluminum, silver, tin, glass and ceramics, but poor adhesion to copper, especially after high temperature and long-term thermal aging, which may cause the oxide film on the other side of copper to have a bad adhesion. Accelerates the thermal cracking reaction of silicone resin. The adhesion of silicone grease to organic materials such as plastics and silicone rubber mainly depends on the surface energy of the latter and its compatibility with silicone resins. Materials with lower surface energy and less compatibility are more difficult to bond. By treating the surface of the substrate (including sanding and priming), especially introducing tackifiers into the silicone resin, the adhesiveness of the silicone resin to the difficult-to-stick substrate can be improved to a certain extent.


use
Silicone resins are mainly used to formulate silicone insulating paints, silicone coatings, silicone adhesives and silicone plastics. High-performance coatings such as high-end building exterior coatings are the main market for silicone resins, and the main varieties are modified polyester and modified acrylic resin. In addition, the consumption of silicone resin in the electronics/electrical industry has grown rapidly, which is also an important driving force for the development of global silicone resin in the future, and the market prospect is very broad.


1. Electrical insulating paint: The volume, quality and service life of electrical appliances have a great relationship with the performance of electrical insulating materials. Therefore, the industry requires the use of a variety of electrical insulating paints, including coil impregnating paint, glass cloth impregnating paint, mica adhesive insulating paint, and silicone paint for electrical and electronic protection.


2. Coating: Silicone resin has excellent heat resistance, cold resistance, weather resistance, water repellency and other properties, in addition, colorless and transparent coatings with good adhesion and wear resistance can be obtained. Anti-sticking release coatings and moisture-proof and hydrophobic coatings .


3. Adhesive: There are two types of polysiloxanes used as adhesives: silicone type and silicone resin type, which are different in structure and crosslinking density. Among them, resin type adhesives are also divided into pure silicone resin type and modified type resin.


4. Plastics: Mainly used in heat-resistant, insulating, structural, and arc-resistant silicone plastics, packaging plastics for semiconductor components, and foamed plastics.


5. Micropowder and trapezoidal polymer: Compared with inorganic fillers, silicone resin micropowder has low relative density, and at the same time has the characteristics of heat resistance, weather resistance, lubricity and hydrophobicity. Trapezoidal silicone resin has higher heat resistance, electrical insulation and flame resistance than general-purpose mesh-shaped three-dimensional silicone resin.


Silicone Adhesive


Silicone adhesives are also called silicone adhesives.


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Among the existing heat-resistant adhesives, silicone adhesives are one of the best varieties. Polysiloxanes used as adhesives can be divided into adhesives based on silicone resin and adhesives based on silicone rubber according to the source of raw materials. The former is mainly used for gluing metal and heat-resistant non-metallic materials, and the resulting glued parts can be used in the temperature range of -60℃~200℃; the latter is mainly used for gluing heat-resistant rubber, rubber and metal and other non-metallic materials Material.


Features


Silicone has good bonding properties to metals such as iron, aluminum and tin, and is also easy to bond to glass and ceramics, but has poor adhesion to copper;


The silicone adhesive based on pure silicone resin is made of silicone resin, mixed with inorganic fillers and solvents, and releases small molecules during curing, which needs to be heated and pressurized;


The curing temperature of silicone resin-based adhesives is too high, and the application is limited;


Add a small amount of ethyl orthosilicate, potassium acetate and silicate glass, etc., the curing temperature drops to 220~200℃, and the high temperature strength is still 392-490MPa;


Pure silicone resin has low mechanical strength. When it is copolymerized and modified with organic resins such as polyester, epoxy or phenolic, it can obtain high temperature resistance and excellent mechanical properties. It is used for high temperature resistant structural adhesives.