The construction of high temperature-resistant silicone coatings is briefly discussed

0 Introduction
High temperature silicone coatings can withstand high temperature (100 to 800 degrees C) oxidation and other media corrosion, that is, in the above environment can achieve stable physical properties, no shedding, no foaming, no cracking, no powdering, no rust, allowing for a slight color change. With the continuous development of industrialization and science and technology, users of high temperature-resistant coating performance and construction conditions put forward higher and higher requirements, not only require coatings at high temperature with excellent heat resistance, corrosion resistance, oil resistance, solvent resistance, etc. , but also require silicone coatings can not only bake curing, room temperature curing, cross-curing, but also through some curing promoter curing agent. Paint industry has a well-known saying, that is, "three-point paint, seven-point construction", can be seen the importance of paint construction, only through the appropriate construction methods, can better play the role of high temperature silicone coatingsIn addition, the quality of silicone coatings themselves is also critical, China's more well-known high-temperature silicone coating brands have "Big Island", "Friends" and other high-temperature-resistant coatings.
1 Cross-linked curing method for silicone coatings
Before talking about the construction of high-temperature silicone coatings, let's talk about the composition of silicone resins and the method of cross-curing. Commonly referred to as silicone resins are polysilicon oxides of highly cross-linked mesh structures consisting of a mixture of methyl triclosane, metformin, benzodiaclosane, debenyldchlorosilane, or methyl-dechlorosilane. The curing of silicone resins is usually achieved by silicone shrinking to form silicone oxygen chains. When the shrinking reaction is carried out, the reaction rate decreases due to the gradual decrease of the concentration of siliconol, which increases the spatial resistance and the flow rate decreases. Therefore, for silicone resins to be fully cured, heating must be performed and catalysts added to speed up the reaction. The ratio of methyl and benzene-based organ groups in silicone resins also has a great impact on their performance. Generally speaking, the lower the benzene-based content, the faster the shrinkage rate, the softer the resulting paint film, and the higher the benzene-based content, the harder the resulting paint film. In addition, the introduction of benzene-based, can improve the silicone resin to pigment wetting, can also improve the silicone resin and other resins of the matching, as well as silicone resin on a variety of substrate bonding force.there are three ways to cross-cur
silicone resins: first, by using hydroxyl on silicone atoms for shrinking polymerization to form a mesh structure, which is the main way for silicone resin cross-curing; Based on the above considerations, a reasonable silicone coating construction plan is formulated.
2 Pre-treatment of silicone coating construction
Silicone coating is generally constructed on metal components, the first metal components for pre-treatment, pre-treatment process is as follows:
(1) first remove the metal components in the processing process produced by welding slag, burrs, oil and other impurities.
(2) for degreasing to improve the cleanliness of the work surface and reduce oil contamination of the sandballs.
(3) for sand blasting and rust removal. The compressed air used in sand blasting must be oil-free and waterless, the compressed air pump should be equipped with oil-water separator, when used should filter compressed air, and regularly release water to oil-water separators and air compressors every day to ensure that compressed air is dry and clean, and the abrasives injected should be dry and clean. In general, the grade of rust removal of metal surfaces shall be carried out in accordance with the relevant provisions of the Grade of Rusting and Rust Removal of Steel Surfaces before coating.
(4) After sand blasting, the oxide layer, rust and dirt on the surface of the metal component should be completely removed and dust and residual impurities removed from the surface of the work piece with dry compressed air or a clean brush.
(5) In order to achieve a better coating effect, blasting projectiles need to use a large number of cleaning solvents to clean the work parts, the relevant tools and appliances used must also be clean and oil-free.
(6) the treated work piece cannot be touched by hand, allowing the work piece to be stored for a maximum period of time of no more than 2 h, if placed too long, the surface of the work piece will rust and affect the quality of the paint film.
(7) If an acid-washed phosphate treatment process is used, the phosphation process should be cancelled when the ambient temperature of the work item exceeds 350 degrees C, as the phosphate film exceeding 350 degrees C will be destroyed.
(8) Finally, apply as soon as possible, the shorter the coating interval, the better. Before coating, if contamination or rust return is found, it should be reprocessed to meet rust removal grade standards.
3 Construction of silicone coatings
Before the construction of silicone coatings, starting from the ingredients, in accordance with the requirements of manufacturers, construction environment, work parts, with special matching thinners to adjust the viscosity of the coating. Dilution approximate dosage: airless spraying, about 5% to 10% (in terms of paint quality, the same between 20%; air spraying, about 15% to 30%; brushing, about 10% to 20%. Different manufacturers, different paint products, thinner dosage is also different; , strictly prevent contamination or damage; after spraying, the surface of the coating film should be free of fluid marks, no leakage spray phenomenon, the thickness of the coating film is uniform, the color is consistent, there must be no rough uneven, hanging, cracks, foaming, peeling and other defects.
normal, silicone coatings are sprayed construction, spray construction needs to pay attention to the following points:
(1) any coating construction must meet the required temperature and humidity conditions, silicone coatings are no exception. The optimal ambient temperature for silicone coating construction is 5 to 40 degrees C, and the ambient humidity is 25% to 85%.
(2) air compressor should pay attention to the installation of oil and water separators, and timed daily oil and water separators, air compressor water, which is very important.
(3) before coating, mask areas that do not need to be coated, such as wedge grooves, shaft holes, finishing surfaces, and some special parts.
(4) before coating, strictly check that the coating equipment is clean and dry, if there is pollution must be treated, so that it meets the corresponding requirements for re-painting.
(5) paint, the use of gasoline and water is strictly prohibited, it is best to use special thinners to adjust the viscosity of the coating.
(6) spray tool, should be cleaned in time, keep clean, dry, to be used next time.
(7) paint film surface to avoid human trampling and mechanical damage in handling.
(8) try to use environmentally friendly high solid silicone coatings, especially brand paint manufacturers of paint varieties.
(9) is cured according to the drying conditions required by silicone coating products to ensure the quality of the paint film.
4 Conclusion
This paper only introduces the conventional construction of high temperature-resistant silicone coatings, and in the high-temperature construction of some special works, there are many changes and uncertainties, which need to be flexible according to objective conditions and environment. Through the above introduction, I hope to improve the relevant personnel's understanding of silicone coating construction, to give full play to the excellent performance of silicone coatings to play a reference role, in order to better promote the use of high temperature-resistant silicone coatings.