The requirements for the mechanical properties of silicone depend mainly on the application. Silicone resins used as electrical insulating varnishes, coatings and adhesives are concerned with hardness, elasticity, thermoplasticity and adhesion. The hardness and elasticity of the silicone paint film can be varied over a wide range by adjusting the molecular structure of the resin. When the content of trifunctional or tetrafunctional link is higher, that is, the higher the crosslink density, a film with high hardness and low elasticity can be obtained; the introduction of a large sterically hindered substituent can improve flexibility and thermoelasticity. It is the reason why the flexibility and thermoplasticity of methylphenyl silicone are superior to those of methyl silicone. Therefore, silicone resin does not need to use a special plasticizer, but the proper combination of soft and hard silicone resin can meet the plasticity requirements.
When used as a certain coating, the hardness of the pure silicone coating film is insufficient, and the thermoplastic is sufficient; if an organically 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 silicone paint films and converting them into harder silica glass. Using a low activity catalyst, since the condensation reaction is incomplete, only a soft coating can be obtained; conversely, a highly active catalyst (such as a compound such as Pb, Al, etc.) can be used to obtain a hard and brittle coating, but some catalysts (such as titanium) The acid ester can effectively increase the hardness of the coating without seriously reducing the elasticity.
Silicone has good adhesion to iron, aluminum, silver, tin, glass and ceramics, but has poor adhesion to copper. Especially after high temperature and long-term heat aging, it may cause the oxide film on the copper surface to have Accelerate the thermal cracking reaction of silicone. The adhesion of silicone grease to organic materials such as plastics, silicone rubber, etc. depends mainly on the surface energy of the latter and compatibility with silicone. The lower the surface energy and the less compatible the material, the harder it is to bond. The adhesion of the silicone resin to the difficult-to-bond substrate can be improved to some extent by the treatment of the surface of the substrate (including sanding and priming), especially by introducing a tackifying component into the silicone resin.
Silicone resin is mainly used as insulating varnish (including varnish, enamel, color lacquer, impregnating varnish, etc.) to impregnate H-class motor and transformer coil, and used to impregnate glass cloth, glass cloth and asbestos cloth to make motor casing and electrical insulation. Windings, etc. Bonding mica with silicone insulating varnish can produce a large area of mica sheet insulation material, which is used as the main insulation of high voltage motors. In addition, silicone can also be used as a heat-resistant, weather-resistant anti-corrosion coating, metal protective coating, construction waterproof and moisture-proof coating, mold release agent, adhesive and secondary processing into silicone plastic for electronic, electrical and defense industries. As a semiconductor packaging material and electronic, electrical silicone resin can be roughly classified into silicone insulating varnish, silicone coating, silicone plastic and silicone adhesive according to its main use and cross-linking method.
Silicone fiberglass cover
Silicone fiberglass cover
Silicone processing additives have unique flexibility and compatibility and have become a key component in the production of pulp and household paper. details as follows:
(1) Electrical insulating varnish: 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 varnish, including coil impregnating varnish, glass cloth impregnating varnish, mica adhesive insulating varnish and silicon lacquer for electronic and electrical protection.
(2) Coating: Silicone resin has excellent heat resistance, cold resistance, weather resistance, water repellency, etc., and can be obtained as a colorless, transparent, good adhesion and abrasion resistance coating anti-adhesive release coating and moisture-proof water coating.
(3) Adhesive: The silicone used as the adhesive has two types of silicone type and silicone type, and the difference in structure and crosslink density. Among them, the resin type bonding agent is also a pure silicone resin type and a modified type resin.
(4) Plastics: mainly used in heat-resistant, insulating, group-proof, arc-resistant silicone plastics, semiconductor component housings, plastics, and foam plastics.
(5) Micropowder and trapezoidal polymer: Compared with inorganic fillers, silicone micropowder has the characteristics of low relative density and heat resistance, weather resistance, lubricity and water repellency. The trapezoidal silicone resin has higher heat resistance, electrical insulation and flame resistance than the silicone resin of the general mesh three-dimensional structure.
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