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    Home > Coatings News > Paints and Coatings Market > Advances in the study of functional powder coatings

    Advances in the study of functional powder coatings

    • Last Update: 2020-11-22
    • Source: Internet
    • Author: User
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    Abstract: Combined with downstream application requirements and the functioning of coatings, this paper discusses the research progress of 5 functional powder coatings, such as high temperature-resistant powder coatings, heavy anti-corrosion powder coatings, low-temperature cured powder coatings, insulated powder coatings and antibacterial powder coatings, and looks forward to the future development of functional powder coatings.
    with the development of science and technology and social progress, traditional general-purpose coatings have been unable to meet the needs of industrial development and people's lives, and the development of coatings with special functionality for different fields has become one of the hot research topics. Depending on the application area, functional powder coatings are available in a variety
    chinese
    . This study summarizes the research status of 5 functional powder coatings, such as high temperature powder coating, heavy anti-corrosion powder coating, low temperature cured powder coating, insulated powder coating and antibacterial powder coating.
    1 High temperature-resistant powder coatings
    high-temperature-resistant coatings are special functional coatings that can withstand high temperatures above 200 degrees C for a long time, the coating does not change color, does not fall off, and can still maintain appropriate physical and mechanical properties, so that protected objects can function normally in high-temperature environments. High temperature-resistant powder coating is based on the original resin base, add silicone resin or the use of silicone modified resin, with curing agents, high-temperature-resistant fillers (such as low melting point glass powder, mica powder, talcum powder, etc.) and pigments, additives, etc. prepared, mainly used in home appliances, such as barbecue ovens, heaters, high-power lighting, and mechanical equipment, such as high-temperature components, such as smoke pipes, high-temperature furnaces, petrochemical equipment.
    the function of high temperature-resistant coatings is related to the molecular structure of silicone resins. Silicone molecular main chain is composed of Si-O-Si, Si-O bond energy of up to 451kJ/mol, far higher than the carbon chain polymer or hybrid polymer molecular main chain C-C and C-O bond energy (345kJ/mol and 335k, respectively) J/mol); At the same time, carbon chain polymers are easily broken chains after thermal oxidation to form small molecular polymers, silicone resin Si atoms connected to the hydrocarbon base by thermal oxidation, is the formation of a highly cross-linked Si-O-Si chain protection layer, which is the silicone resin has better heat resistance of the direct cause. When the high temperature is reached,
    coating is used to achieve "secondary film".
    for the "secondary film", Wang Hai overseas and other combination of the two silicone coatings previously proposed high temperature resistance, think that for different silicone coating systems, there are different "secondary film" system. The results show that when the coating components contain low melting point glass powder, low melting point glass powder is the main cause of coating "secondary film". Silicone high temperature-resistant coating in the heating process, first formed a loose SiO2 layer, when the melting point of glass powder, glass powder began to melt into a film, replacing silicone resin on the pigment adhesion, so that high-temperature coating "secondary film", thus playing a high-temperature insulation of the substrate anti-corrosion effect.
    , Zhao Guanglin and others prepared a high temperature-resistant powder coating to study the changes in color difference, gloss and impact resistance of the coating at high temperatures. The results showed that the long-term heat resistance of the high temperature powder coating reached more than 450 degrees C, and the coating performance decreased slightly with the increase of baking temperature and the increase of baking time. The coating performance has changed considerably under baking conditions of 300 degrees C/1h and 500 degrees C/10h. The former is due to the evaporation of small molecules in the coating system and changes in some unstable groups in the polymer, while the latter is due to sudden changes in performance caused by carbonization of organic parts of the coating. At the same time, Zhao Guanglin and so on also in the formula of the components of the
    use of the explanation, pointed out that a variety of filler ingredients can obtain a good comprehensive performance of the coating, when the amount of filler addition is 50% of the total amount of the formula, the comprehensive performance of the coating is the best. Song Linyong and others use silicone resin to mix and change epoxy resin, and select inorganic pigment fillers to prepare heat-resistant powder coating, the results show that: by adding 10% to 30% silicone resin in epoxy resin, and The selection of mica powder and the appropriate amount of composite antioxidants can significantly improve the heat resistance of powder coatings to more than 300 degrees C/70h, and the coating has good physical properties, while reducing the color change effect of the coating. He Tao and others studied the effect of antioxidants on the heat resistance of β TGIC cured powder coatings, and the results showed that adding 1% to 3% of antioxidants improved the heat resistance of the coating in the range of 230 to 270 degrees C. 4-hydroxybenzene) propylene acid) tetrylitol esters and auxiliary antioxidants 168 (2,4-two-sbutyl benzene) phosphates) according to 1:1 compounding has a better synergistic effect, antioxidant dosage increased to more than 5%, the degree of thermooxygen inhibition at high temperature of the coating is no longer obvious.
    2 Heavy anti-corrosion powder coatings
    Heavy anti-corrosion powder coatings based on epoxy resins, also known as fused epoxy powder coatings (FBe), are mainly used in the internal and external wall coating of pipelines for the transportation of natural gas, crude oil, refined oil and other chemical products, as well as the coating of building materials, electrical insulation materials, automotive components materials.
    FBE through heating melt curing on the metal pipe to form a certain thickness of the protective layer, the coating has excellent adhesion, low oxygen permeability, anti-microbial corrosion, no cathode shielding, hard wear resistance, coating surface smooth and corrosion resistance, is currently one of the most widely used pipeline protection means. As the inner protective layer of the pipe, the FBE coating can be effectively anti-corrosion and safe and hygienic, and the flow resistance of the conveying fluid is small, and as the outer protective layer, it can be combined with cathode protection to provide long-term effective protection for the buried pipe.
    The corrosion of the inside and outside surfaces of the buried pipe is different, the process of corrosion of the outer surface is mainly due to the electrochemical corrosion of the soil (including soil stress, microorganisms, electrolytes and other factors), while the corrosion of the inner surface is mainly due to the chemical corrosion and fluid flushing corrosion caused by different conveyor mediums in the pipe. Combining the corrosion effect and cathodic stripping mechanism inside and outside the buried pipe mentioned above, Shi Ligong points out that the key to long-lasting corrosion protection of the pipe coating lies in the cross-link density, thickness and adhesion with the substrate of the FBE coating, so the formula of FBE must be reasonably designed and coated and cured according to the correct process in order to ensure the long-lasting corrosion of FBE.
    Yulin starts with the molecular structure of epoxy resin, modifies the epoxy resin, reduces the content of the large molecular chain segment, makes the resin narrower relative to the molecular mass distribution, reduces the heating melt viscosity, improves the processing flow energy, and at the same time, the modified resin molecular structure contains more hydroxyl and other polar groups, and contains flexible structural units, reduces the internal stress during the coating curing
    cooling process, and improves the adhesion between the coating and the metal substrate. The results show that the powder coating prepared by modified epoxy resin can meet the new standard of coating anti-cathode stripping of buried steel pipe at 1.5V protection voltage of 70 degrees C/30d. From the point of view of electrochemical protection, yan Bing and so on, using the principle of sacrificing zinc to protect the steel substrate, using scaly zinc powder to develop zinc-based heavy anti-corrosion powder coating, and with pure polyester powder coating compound applied to the surface coating of highway guardrails in Guizhou Province. The results show that after more than 5a application tests, the above-mentioned double coating protection system has outstanding anti-corrosion ability, fully meets the requirements of the relevant standards and norms of the national and transportation industry, and can replace the hot galvanizing in a certain range to avoid the environmental pollution caused by the galvanizing process. Yin Xianxia and other detailed study of the formulation design of modified epoxy heavy anti-corrosion powder coating, the results show that: when the phenolic eoxygen / bisphenol A epoxy ratio of 70/30, catalyst metformin dosing 0.7% to 0.8%, filler precipitation sulfate and active silicon micropowride quality ratio of 1:2, curing conditions of 230 degrees C / 90s, the coating performance is the best. The study of substrate shows that the modified epoxy heavy antiseptic powder coating has good leveling and coating performance when spraying the inner and outer walls of the iron plate, aluminum profile, galvanized steel surface and pipe, but the above problems can be improved by adding additives when spraying the cast porous substrate and the complex construction surface. Hu Yong'an discusses the construction process of heavy anti-corrosion epoxy powder coating, and for the external coating process, the double-layer structure formed by the standard heavy anti-corrosion epoxy powder coating as the base and the improved heavy anti-corrosion epoxy powder coating as the outer layer can improve the physical properties of the coating, high temperature resistance and anti-permeability under high temperature conditions; Diameter, batch, etc. adjust the relevant process parameters to achieve resistance reduction and protection of the two major effects, for epoxy and polyethylene composite 3PE coating, it is necessary to grasp the pre-treatment method, electrostation spraying method and film thickness, adhesive coating time, polyethylene layer and adhesive layer binding method 4 key points, so that the three layers of connection to form a whole.
    3 Low-temperature curing powder coating
    Although powder coating has the advantages of non-polluting, excellent comprehensive performance, but compared to solvent-based coatings, the usual thermostatized powder coating curing temperature is higher (180 to 200 degrees C), curing time is longer (10 to 30min), restricting powder coatings can only be applied to heat-resistant metal substrates, but not for wood, paper, plastic and other thermally sensitive substrates. At the same time, higher curing temperature and longer curing time also consume a lot of heat. The general baking temperature can save about 10% of energy for every 10 degrees C reduction, therefore, from the aspects of energy saving and consumption reduction and expansion of the application field, low temperature curing powder coating research has become an inevitable trend.
    the curing process of a powder coating is the process by which the official energy groups between the resin and the curing agent react with each other to form a coating with a three-dimensional chemical cross-linking network structure. From the point of view of reaction dynamics, the size of the reaction rate depends on the reaction rate constant and the concentration of the substance in the reaction ernum group, where the reaction rate constant is inversely related to the reaction activity energy and is directly related to the reaction temperature. Therefore, the selection of resin and curing agent system with high reaction activity group, reducing the average relative molecular mass of reactants, especially resins, increasing the concentration of substances in the reaction group, and adding curing promoter are all helpful to achieve the low temperature curing process. However, these measures also affect the processing performance of powder coatings and the materialization properties of coatings. At the same time, low-temperature cured powder coatings are often faced with poor storage stability, powder easy to cling to the problem. Therefore, how to balance the relationship between the above properties is the key issue to be considered in the research process of low temperature curing powder coating.
    MaZhiYi for the β-hydroxyacetamide system low-temperature curing powder coating, from the perspective of regulating the molecular structure of polymers to synthesize a new polyester resin, compared with synthetic polyester prepared powder coating and ordinary polyester prepared powder coating storage stability and coating performance. The results show that synthetic polyester has higher reaction activity than ordinary polyester, and the powder coating prepared by it can achieve low temperature curing of 140 degrees C/(20 to 30) min condition, while the powder coating has the appropriate viscosity and glass transition temperature, and the coating has excellent impact resistance. Garcia and others studied the mechanical and thermal properties of bisphenol A epoxy/Meldrenic acid (MA) copolymeration systems based on TEFS Comparing the epoxy system, the results show that the curing time of the copolymer system at 120 degrees C is about 80% shorter than that of the TBG system, about 60% shorter than that of the ermereum system, and the coating of the copolymer system also shows excellent adhesion and mechanical properties. Sun Guoliang and others used 4,4-diphenyl methane diocyanate (MDI) and 3-dimethylamine as raw materials to synthesize an organic pyrethroid cryogenic curing agent diphenyl methane-4,4-ii(N, N-dimethylamine). The improved process for the production of powder coatings allows epoxy powder coatings to be fully cured at 130C/8min and 140C/4min, with good leveling and storage stability, excellent coating physical mechanical properties and chemical resistance.
    4 Insulation Powder Coatings
    in 1907 Becklade developed phenolic resins to mark the birth of electrical insulation materials, which have developed rapidly since then. Insulation materials are materials with low conductivity that can be used to isolate charged bodies with different capacitions. Insulation powder coating as one of the varieties, mainly composed of polymer resin substate and inorgeable non-metallic fillers, with excellent insulation performance and green characteristics, highly competitive and promising prospects, widely used in motors, electrical appliances, automotive industry, aviation machinery and other fields.
    in the field of insulation coatings, depending on the performance and use of different needs can choose different film-forming resins, including polyester resin, epoxy resin, polyurethane resin, silicone resin and so on. Hu Bai9 and other insulation powder coating for electromagnetic wire, epoxy resin as the base, to study epoxy resin, curing agent, filler type and dosage of the effect on coating performance, and epoxy / polyester powder coating performance compared.
    results show that the epoxy powder coating is better than the epoxy/polyester system by applying epoxy powder coating to the round aluminum wire coating of the electromagnetic line, softening the perforation temperature range to 140 to 150 degrees C, and the coating flexibility, heat resistance and electrical insulation are better than the epoxy/polyester system. The results of the study on thinly coated insulated powder coating for new energy vehicle batteries show that: the epoxy resin produced by two-step method is selected, and the curing agent is matched according to the epoxy equivalent, and the mimi catalyst of 0.3% to 0.6% can be added to form a dense continuous coating; The battery coating of new energy vehicles with thickness of 100 to 150 m has excellent electrolyte resistance, insulation performance and moisture and heat resistance, and the pass rate of customer on-site spraying is 97%. WenWen and so on for the shortcomings of poor weather resistance of epoxy powder coating, from the point of view of resin composition, the preparation of epoxy-type acrylic resin applied to insulated powder coating, while the introduction of potassium hexatinate crystal filler to improve the impact resistance of the coating. The results showed that when the amount ratio of the curing agent to the active group material of the resin was 1:1, and the content of methyl acrylic shrinkage glyceride (GMA) in the resin synthetic monomer was greater than 30%, the comprehensive performance of the coating was the best, and the addition of 2% potassium hetium hetate could effectively improve the impact resistance of the coating, and the electrical properties of the coating met the application requirements of the insulated powder coating.
    5 Antibacterial powder coating
    Antibacterial powder coating has antibacterial, can kill or inhibit bacteria attached to the coating, widely used in home appliances, automotive and other fields. The functionalization of antibacterial coatings is achieved by adding antibacterial agents to the coating. Since powder coatings are solvent-free, the antimicrobials required to be added have good compatibleity with the remaining parts, do not cause changes in paint color, odor and stability, and can withstand the temperature at which powder coatings are processed and cured. In addition, antibacterial agents are required not to affect powders
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