Curing Method and Application of Silicone Resin

Feb 7, 2021

According to their main uses and cross-linking methods, silicone resins can be roughly divided into silicone insulating varnishes, silicone coatings, silicone plastics and silicone adhesives.

Silicone resin is mainly used as insulating paint (including varnish, enamel, colored paint, impregnating paint, etc.) to impregnate H-class motor and transformer coils, and to impregnate glass cloth, glass cloth silk and asbestos cloth to make motor casing and electrical insulation Winding etc. Using organic silicon insulating varnish to bond mica can make a large area of ​​mica sheet insulating material, which can be used as the main insulation of high-voltage motors.

In addition, silicone resin can also be used as heat-resistant, weather-resistant anticorrosive coatings, metal protective coatings, waterproof and moisture-proof coatings for construction projects, release agents, adhesives, and secondary processing into silicone plastics for use in electronics, electrical and defense industries Above, as semiconductor packaging materials and insulating materials for electronic and electrical parts.

There are roughly three ways to cure and crosslink silicone resins: one is to use the hydroxyl groups on the silicon atoms to shrink and polymerize and crosslink to form a network structure, which is the main way to cure silicone resins, and the other is to use ethylene connected to the silicon atoms. Base, using organic peroxide as a catalyst, similar to the way of silicone rubber vulcanization: the third is to use the vinyl and silicon-hydrogen bond connected to the silicon atom to carry out the addition reaction, for example, solvent-free silicone resin and blowing agent can be mixed Get foamed silicone resin.

The introduction of epoxy groups in silicone resins to obtain epoxy-modified silicone resins has been the research hotspot of modified silicone resins in recent years. The performance of coatings based on epoxy-modified silicone resins at home and abroad has also been in recent years. Promoted by the research results of the company, it has been continuously improved, especially with the further research on the compatibility of the two phases and the emergence of new curing agents, the application of various developed high-temperature anti-corrosion protective coatings in the protection of materials It is also becoming more widespread. The epoxy modified resin has good adhesion, medium resistance, water resistance, and atmospheric aging resistance. It can be cured with an amine curing agent, or even at room temperature, which greatly reduces the curing temperature of the silicone resin. The modified resin can be used for a long time in the range of -60 ~ 200C

Silsesquioxane (Silsesquioxane) refers to an organic silicon compound with a molecular structure of RSiO32 with a special organic hybrid structure. Cage-shaped silsesquioxane (Polyhedral Oligomernic Silsesquioxane, POSS for short), also known as cubic or spherical POSs, is currently One of the most widely studied silsesquioxanes. The application of POSS can be divided into two aspects:--It is used as an organic-inorganic hybrid component to realize the chemical bond between organic and inorganic to form an intramolecular hybrid polymer material; the other is as an additive: additive, which can be different Improve material performance
1.1 Raw materials
Trimethoxysilane, tetramethoxysilane, r-aminopropyltriethoxysilane: industrial grade, Wuhan University silicone; hexamethyldisiloxane: industrial grade, Xinghuo Chemical; triethylamine: analytical pure,
1.2 Synthesis of MQ resin
First, tetramethoxysilane and hexamethyldisiloxane are mixed in a three-necked flask in a fixed ratio of--, a certain amount of water is added dropwise after adding the catalyst, and after hydrolyzing for 8 h, the solvent is separated by vacuum and evaporated to obtain a colorless Transparent MQ resin (2).
1.3 Synthesis of epoxy group-containing siloxane
3-Methyl-7-oxabicyclo[4.1.0] heptane and 930 were mixed in a three-necked flask according to the proportion, added with catalyst and triethylamine, and reacted for 24 hours at room temperature, isolated from moisture, and then vacuumed to remove low-boiling substances. product.
1.4 Synthesis of epoxy modified silicone resin
Add MQ resin to a single-neck flask, add a certain amount of methanol, ammonia, dropwise add epoxy group-containing siloxane to the flask, stir at room temperature for a period of time, after the reaction is completed, vacuum distillation (intermittently heated to 100C) .
1.5 Synthesis of amino cage silsesquioxane
First, a quantitative amount of distilled water, ethanol, acetonitrile, triethylamine, and tetramethylammonium hydroxide are sequentially added to the three-necked flask. Then γ-aminopropyltriethoxysilane was added dropwise, and the mixture was refluxed and stirred at a constant temperature of 70C for 18 h. The solvent was removed by heating and vacuum to obtain a crude product. After washing the crude product with a solvent, the solvent is extracted in a vacuum to obtain a yellow transparent viscous gel-like final product.