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China Coatings Online News Information: Jiang Xiujie, Cui Xianlin, Wang Tongliang, Cold Xiaofei, Wang Zhichao (Marine Chemical Research Institute, Qingdao, Shandong 266071)
Abstract: Organic modified polysilicae hybrid coatings are a new generation of high-performance protective coatings, widely used in marine installations, petrochemical equipment, industrial protection and bridges, airports, stadiums and so on. This paper summarizes the types and properties of organic modified polysilicae hybrid coatings and the problems to be solved in the field and their development prospects.key words: protective coatings
silicone oxane
hybrid coatings
: TQ637 document identification code: A article number: 1007-9548 (2009) 10-0031-03
1 Introduction
since the mid-1990s, Since the industrialization of epoxy polysilicae hybrid coatings, the research of organic modified polysilane hybrid coatings has developed rapidly, becoming the fastest and largest field in the coating industry in recent years, and with its excellent durability, high solids, low VOC and non-isocyanate curing advantages, has become the ideal product to replace polyurethane finishes, epoxy acrylic finishes, fluoropolymers and other high weather-resistant finishes. A large number of laboratory studies and practical applications have proved that the dual coating system using a fatty family of epoxy polysilane paint on zinc-rich primers is equivalent to or even exceeds the traditional three-coated and more coating systems in performance, and is widely used in offshore installations, petrochemical equipment, wind power equipment and industrial protection with its better corrosion resistance. Acrylic polysilicae coatings are widely used in infrastructure such as bridges, airports, tv towers, sports stadiums and so on because of their excellent weather resistance and appearance decoration. With the deepening of research in this field, more organic structures will be introduced into the molecular chain of polysilioxane, and the performance of existing products will be continuously improved, and the application of silicone oxyane hybridization coatings will become more and more extensive.2 Silicone oxygenation technology
Epoxy, polyurethanes and other organic coatings degrade due to thermal oxidation, light-triggered oxidation or chemical corrosion, resulting in discoloration of the coating film, reduced gloss, flexibility, adhesion and reduced corrosion resistance, thereby reducing the durability and service life of the coating film.silicone oxycodane hybridization technology is the use of the versatility of polysilioxane, through a shrink reaction to connect a variety of organic functional groups to the main chain of inorganic polysilicone, the main chain repeat Si-O key energy (452k) J/mo)l is higher than the C-C bond (350kJ/mo)l of organic polymers, so it is resistant to UV rays, and its oxidation state makes it particularly resistant to oxygen and other oxidizing substances, so silicone oxidane hybrid coatings are more resistant to degradation than organic coatings. At the same time, organic change balances the flexibility and adhesion of polymers and reduces production costs.for modified organic resins can be selected acrylic polyurethane, epoxy and a variety of modified acrylates (with epoxy, hydroxyl, amino and sioxyxane). Polysilica is mostly silicone resin intermediates containing alkyl or silicone alcohol with a relative molecular mass of 600 to 1000, and silica classes containing motor groups. A variety of silicone oxyane hybrid coatings on the market, organic resins accounted for 20% to 70% of the solid content of resins. Some studies have pointed out that according to adhesion and outdoor hanging plate and laboratory accelerated durability testing, 20% to 30% of organic modified can obtain better paint film performance. The application depends on the correct screening of organic resins and the moderate change of polysilane, so as to achieve a balance between construction and paint film performance.the curing reaction of 2.1 silicone oxide
In silicone oxyane hybrid coating, there are multiple cross-linking reactions, and the network structure formed by polymerization is more complex.
Currently, most varieties of organic modified polysilicae hybrid coatings are cured with aminosiloxyane, such as Dynasylan AMEO, AMMO, etc., where an open-loop addition of epoxy and amine or a double bond reacts with a melgar of amine, solidified The silica-alkyl group/polysilicae resin of the chemical agent under wet conditions under hydrolytic polymerization reaction, if necessary, can be added to the organo tin and other metal organic matter as a catalyst to speed up the shrinkage reaction;
characteristics of 2.2 silicone oxyane hybridization are as follows
key features of silicone oxyane hybridization technology are as follows.
(1) High solids, low VOC content, low toxicity polyurethane paint VOC content is usually 340g/L, or even 420g/L, to reduce to 250g/L or less is still technically difficult. Other high weather-resistant finishes, such as acrylic finishes and organic fluorine coatings, also have low solid content and high VOC problems. With the improvement of HSE (Health, Safety and Environment) laws, the content limit of VOC is more stringent, resulting in great restrictions on the application of these products. The polysilicae resin system has a very low viscosity, by organic matter modified hybridization technology can be equipped with high solid content, low VOC system, according to the hybrid formula, VOC can be as low as 100g/L. The non-isocyanate curing process and the repeated Si-O bonds on the main chain make it difficult to burn and avoid the large amount of smoke and toxic gases produced when organic coatings burn.(2) color and gloss hold is excellent
gloss hold reflects the coating's ability to withstand heat and light oxidation degradation. Epoxy and alkyd paints earlier showed powdering and fading, polyurethane and acrylic finishes also showed fading and loss of light after 3 to 5 years of exposure, while silicone oxycodane hybrid coatings were more biodegradable due to repeated Si-O bonds on the main chain, maintaining initial color and gloss over a longer period of time. A large number of QUV accelerated weather resistance tests and atmospheric natural exposure tests have proved that silicone sioxane hybrid coatings have better color and gloss hold than organic coatings.(3) wear resistance, stain resistance and graffiti resistance is excellent
silicone polysilioxane hybrid coating film because of high cross-link density, has a higher glass transformation temperature, coupled with the silicone main chain and give the coating film a lower surface pressure, so it has good stain resistance;(4) low cost
the use of silicone oxycodane hybrid coating can effectively reduce the cost of protection, which can be analyzed from the following aspects: (1) performance factors: improved color and gloss hold, paint durability, long service life; 2) Health, safety and environmental factors: reduce the release of VOC, reduce the occurrence of accidents in the production, storage, transportation and construction process, no isocyanate, not easy to burn, etc.;3 polysilicae hybridization type
the earliest production of silicone oxide hybridized coatings selected organic resin is adipose ethylene, followed by acrylic, acrylic polyurethane. With the further development of research, the introduction of vinyl resin, ethylene acetate resin, fluoropolymer, elastic epoxy and phenolic resin system in polysilicaene has been further developed.3.1 ethylene polysilicae hybrid coating
the earliest industrialization of hydrogenated adipose family epoxy modified polysilicae, for Ameron's products PSX700 , solid content of 90%, VOC content of 12 0g/L, combining the corrosion resistance of epoxy with the weather resistance of adipose polyurethane in a coating, combined with zinc silicate primer, enables a single hybrid coating to replace the intermediate layer of epoxy and polyurethane paint, thus maintaining considerable weather resistance and corrosion resistance.
a large number of laboratory studies and coating standards have verified that epoxy polysiloxyne hybrid coatings have good durability. At present, the more demanding performance tests in anti-corrosion coatings are Norsok standard M-CR-501, which includes a 6000h salt spray test, a 6000h compression chamber test, a 4200h interval salt spray and an ultraviolet light cycle test. The application of inorganic zinc silicate or zinc-rich primers 75 m and epoxy polysilicae primers on steel plates polished to Sa2, 125 m, successfully passed the test; According to the ISO12944 steel structure anti-corrosion coating series standards, 75 m epoxy zinc-rich primer and a single 125 m epoxy polyoxyoxyxane finish passed the C5-M high ocean corrosion environment durability test. The 40 m zinc-rich primer and the 140 m epoxy polysiloxane finish have passed ACQPA performance tests. Zinc-rich primers and epoxy polysiloxane paint ii coating systems exhibit better corrosion resistance than other coatings in 18 U.S. Navy corrosive tests of 18 coating systems, including salt spray tests, electrochemical impedance spectra, and live ship mounting plate tests.second generation of epoxy polysilioxane products is based on the first generation, changed the type and content of silicone side chain sioxane, thereby improving the flexibility of the product. At present, major coating companies have developed and launched a third generation of epoxy polysilica products, such as the Danish old man coating company Hempaxaneclassic 55000 and Hempaxanelight 55030, while maintaining the excellent weather resistance and high mechanical strength of the previous generation of products, while further improving the flexibility of the product, focusing on improving the re-painting performance of the coating, can provide a broader and safer re-coating performance on the base paint and polysilane coating.Replacing the adipose epoxy with aromatic epoxy to polysiloxyne modified to obtain chemical resistance to good ethylene phenolic polysilioxane hybrid coating, can withstand high concentrations of inorganic and organic acids, alkalis, solvents and oxidizing substances, etc., can be used in storage tank walls and concrete floor coatings. In order to reduce the high cross-link density of the coating system and shrinkage caused by coating cracking, shedding and other problems, the choice of modified flexible cycloxysiloxytan hybrid coating is a better choice, this kind of coating is particularly suitable for use in pipelines, paper mills, chemical plants and other requirements of high chemical resistance, is an alternative to MDA and aromatic / lipid cyclamine cured epoxy ideal products.3.2 Acrylic polysilicae hybridized coatings
The earliest acrylic polysilica hybrid coatings entered the market in the late 1990s as a single-component medium solid content (volume fraction 55%), with excellent weather resistance, powder resistance, corrosion resistance and flexibility in the construction of single-component products. It was originally designed to replace isocyanate cured two-part acrylic polyurethane, but the price is not dominant, and the low content of sioxane, weather resistance is less than ethylene oxide polysilane and the subsequent emergence of two-part acrylic polysilica coating. Then developed a second generation of single-part acrylic polysilicae hybrid coating, which does not exist during construction mixing, construction time is limited by the applicable period and excessive ingredients caused waste, and on the basis of the first generation of products to increase the solid content to 80% (volume solid content), VOC content from 384g/L to 262g/L, with higher silicane content, improve weather resistance, especially suitable for marine and industrial protective coatings.two-part acrylic polysilioxane and ethylene acrylic polysilica, polyurethane acrylic polysilica hybrid coatings and other products also occupy a certain market, such as Interfine878, Interfine979, Jotun Hardtop PSO, solid content of more than 70%, VOC less than 250g/L, with excellent weather resistance. Experiments show that polyurethane acrylic polysilicae hybridization coating is the most flexible silicone oxytane hybrid coating, and its flexibility is even better than polyurethane.3.3 fluoro-modified acrylic polysilicae and epoxy polysiloxyne hybrid coatings
fluoropolymers have excellent weather resistance, but low solid content and high VOC content.
fluoropropylate polysilica and fluorooxysiloxyne hybrid coatings maintain excellent UV resistance and weather resistance of fluoropolymers, while maintaining the characteristics of high solid and low VOC of acrylic polysilica and ethylene polysilica. The acceleration test shows that it is significantly higher than the adipose family ethylene oxide in terms of weather resistance, and even higher than acrylic polysilica, while maintaining good corrosion resistance. The type of fluoropolymer used for the modified determines the degree to which the performance of the hybrid product is improved.
3.4 thin-film silicone oxyane hybrid coating
the current market polysilicae hybrid coating is a thick film products, a typical single dry film thickness of 100 to 150 m, thick film products to replace the traditional epoxy intermediate layer / polyurethane finish paint provides the basis. Recent studies have reduced the thickness of the paint film to the extent of a typical two-part polyurethane finish, the thickness of the dry film is 40 to 75 m, still has excellent weather resistance, low solvent content, and does not contain harmful isocyanate. Such products in the equipment production plant has a large application market, due to reduced production costs, the potential to replace polyurethane paint is great.4 Silicone oxygenation coating
Resoled problem to be solved
(1) to improve the silicone oxytane hybridization coating on the primer or thick film middle layer adhesion, that is, to improve the system's inter-layer "tolerance." In addition to ethylene oxide polysilane coating system has a wide range of options, with most epoxy zinc-rich primer, inorganic zinc silicate primer, low-surface treatment epoxy primer and the middle layer has a good compatible, other polysilica oxide on the primer, especially inorganic primer adhesion is very limited.(2) to improve the "tolerance" of silicone oxyane hybrid coatings to different dry film thicknesses. Some products are too thick for construction, due to the curing process coating cross-link contraction caused by the internal strain, resulting in the coating's impact resistance, flexibility and other performance decline, serious will cause the coating cracking, shedding. It should also be taken into account that the coating system does not fully react during the early curing phase of alkysilane in the long-term use of cross-curing, making the problem further aggravated.(3) to improve the "tolerance" of silicone oxycodane hybrid coatings to re-painting time, providing a wider and safer re-painting performance. Because the coating system has a high cross-link density, multi-layer construction should fully take into account the problem of re-painting time, otherwise it will fall off due to poor inter-layer adhesion. Shorter re-painting time can ensure faster construction of the lower coating, improve efficiency, and longer or even no maximum re-painting interval, the surface treatment of the substrate requirements