In addition to carbon, nitrogen, oxygen, and sulfur atoms, the main chain of the element-free organic polymer compound is composed of atoms of other elements, and it is a compound between organic polymers and inorganic compounds. The main applications in coatings are silicone polymers, organic fluorine polymers and organic titanium polymers. Element organic polymer coatings (code W) have unique high temperature resistance and weather resistance, and good insulation, chemical corrosion resistance, water resistance, and cold resistance. They have important roles in aerospace, electrical engineering, nuclear energy and daily necessities. Uses have become a large category of varieties.
(1) Silicone resin coating
Silicone coatings are coatings . Silicone has Si-o bond as the main bond, and the Si-0-Si main chain will not be broken until 350C, while the general organic high polymer has already been completely cracked at this temperature, and the Si-O bond can reach 443.5kJ/mol , so that the organosilicon has the same structural unit as the silicate inorganic substance, and the heat resistance is very good; at the same time, the organosilicon has the properties of some organic substances because of the Si-C group. This duality makes the organosilicon polymer not only have heat resistance In addition to fire resistance, hardness and hardness, it also has the characteristics .
A notable feature of silicone coatings is their high heat resistance. The coating made of silicic acid resin and heat-resistant pigments and fillers can be used for a long time at 200~300°C; the organosilicon zinc powder paint can withstand the high temperature of 400°C for a long time; the organosilicon aluminum powder paint can withstand the high temperature of 500°C for a long time, It can reach 600~800C (200 hours) in a short period of time, and can withstand high temperatures of 1200C in an instant . At the same time, its cold resistance is also very good, and it still has high flexibility . Another feature of silicone coatings is very good weather resistance, and the gloss retention of silicone-modified polyester resin paints is even better than that of fluororesin coatings. Coatings modified with silicones for alkyd, amino, and acrylic resins are superior to vinyl and acrylic resin coatings, and have excellent weather resistance, gloss retention and color retention. Silicone coatings are resistant to boiling water and steam, and have good electrical insulation, but are more expensive. It plays a very important role in the manufacture of motors, electrical equipment and electronic devices. Its heat resistance grade is 180C, which belongs to H insulating material. The dielectric constant, electric breakdown strength, and insulation resistance do not change much within - 50 ~ 250C. It can be used in high-low frequency ranges, and it is resistant to moisture, acid and alkali, and Radiation, ozone, corona, flame and non-toxic.
Silicone resin coatings can be used for the insulation of motors and transformers, as well as for the coating of electrical and electronic components , glass fibers, and asbestos woven fabrics, and for the coating of aircraft and ship engines, stoves, boilers, ship chimneys, and automobile exhaust pipes. Apparatus, the coating of ablative thermal insulation coating on the surface of spacecraft. Silicone- modified alkyd coatings are used for heavy anti-corrosion paints and coating protection for permanent steel structures (such as high-voltage transmission towers, railway bridges, oil drilling equipment, etc.). Silicone-modified polyester paints can be used for sheet , architectural pre-painted sheet metal, aluminum roof panels, etc. Organosilicon coatings can also be used in rubber and plastic products industry and gold chip casting, release paint in glass products, anti-sticking and plastic protective coatings. Silicone coatings are self-drying and baking, and there are one-component and two-component packaging types. With the increasingly stringent requirements for performance, energy saving and environmental protection, many new varieties of silicone coatings have been developed in recent years, such as silicone water-based coatings (water-soluble and emulsion type), low temperature and normal temperature coatings with good heat resistance Curing silicone coatings, solvent-free silicone coatings, light-curing silicone coatings, electron beam curing silicone coatings, scratch-resistant hard film coatings on plastic surfaces, silicone coatings on glass fiber surfaces for optical cables, silicone waterproof coatings for construction, etc.
(2) Organic fluorine resin coating
Fluorine resin is a polymer . They are prepared by homopolymerization and copolymerization of fluorine-containing monomers, or copolymerization of fluorine-containing monomers and ethylene . There are many types of organic fluorine resins, such as polytetrafluoroethylene, polytetrafluoroethylene-hexafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-trifluorochloroethylene, polytrifluoroethylene, polytrifluorochloroethylene, tetrafluoroethylene Ethylene -hexafluoropropylene copolymer and polyvinyl fluoride, etc.
The CF bond energy in the organic fluorine resin structure is extremely high, up to 477kJ/mol, so the thermal stability very good, generally it can be used for a long time at 100~250°C, and it can still maintain a certain stability when used at -80~-195° flexibility. PTFE has broad high-low temperature resistance, long-term use temperature is - 250 ~ 260C, and can be used for 10,000 hours at 210C, and it is completely non-flammable. Fluorine atoms have a shielding effect on the CC chain skeleton, so organic fluorine resins have excellent chemical stability, and can resist acids, alkalis , organic solvents, high-temperature media, and even liquid oxygen oxidation. Organic fluorine resins have very good weather resistance , and some coatings can withstand atmospheric exposure for up to 25 years.
Most organic fluorine resins do not burn, and some species are self-extinguishing even if they burn. They have good water resistance and basically do not absorb water. The water absorption rate of polytetrafluoroethylene and polytetrafluoroethylene-hexafluoropropylene is zero . It has excellent electrical properties, and its performance is not affected by the temperature, humidity and operating frequency of the working environment. The surface energy of organic fluororesin is extremely low, the adhesion is very small, the coefficient of friction is also very small, and the surface is non- sticky .
Organic fluorine resin coatings can be made into suspension dispersion type and solvent type. After dipping and spraying, the suspension dispersion type coating must be dried, high temperature or melt plasticized and sintered; the solvent type coating needs to be sprayed several times to form a film. Powdered resins can be applied by plasma spraying. Due to the excellent properties of organic fluorine resin coatings, it has been widely used in coatings. The skin coating of the fourth-generation fighter jets in the United States uses fluorine-containing coatings, and the service life can reach more than 10 years. Non-stick cookware coatings are widely used. Fluorine-containing coatings can have . Glass fiber and asbestos fiber impregnated with PTFE dispersion can be used to make laminated boards. Organic fluorine resin coatings are widely used as anti-corrosion coatings. For example, polytrifluorochloroethylene coating on the inner walls of sulfuric acid reaction towers and hydrochloric acid bath towers is more durable than linings of lead plates, phenolic plastics, and asbestos mortar. Organic fluorine resin coatings can be used as coatings for oil pipelines, coatings , coatings for food machinery surfaces and inner walls of cans, etc. It can also be used as a release agent due to its non-stick properties.
(3) Organic titanium polymer coating
The most widely used is the butyl orthotitanate polycondensate solution as the paint base, adding modified resin and aluminum powder, which can withstand high temperature of 500C. Using zinc powder as a pigment not only can withstand high temperature, but also has anti-corrosion properties.
