Acrylic Matt Powder Coatings
Abstract: The new matt acrylic powder coating successfully for the powder coating industry in China has opened up new areas of technology, the article discusses the development of many technical issues need to be resolved in the paint.
The powder coating rapidly forward, an endless stream of new varieties. Indoor powder coating polyester – epoxy (mixed type) as the representative in China has for many years. Varieties of high-gloss, flat, half-light, low light (also known as matte), matte, texture, etc., these products have been technically very mature. Hybrid powder coating in China dominated, accounts for about 70 to 80 percent of the total output.
Outdoor powder coating polyester-TGIC type, although the relatively late development, but a few years have made great progress. The object of the use of outdoor powder coating first air conditioner enclosure, film gloss of about 80% to 95%, belong to the high light areas. Performance of pure polyester outdoor powder coating, using the increasingly wide range of components such as transport vehicles, agricultural machinery parts, steel, aluminum alloy doors and windows, road divider, lampposts column, outdoor metal furniture, etc., some indoor durable products such as refrigerators, washing machines, ceiling, outdoor powder coating paint. Since different products have a different appearance requirements, the end of the single high light coating can not meet this demand, so there is no light outdoor powder coating.
2 acrylic matte Powder Coatings
Powder coating manufacturers, research institutes, universities, paint additives, factory, etc. in different ways from different angles, different gloss outdoor powder coating research and exploration. Summarized in the following four ways:
- Some with extinction effect of the filler;
- Different types of polyester resin manufacturing powder, and then to dry the two powders mixed with the incompatibility of these two powders to achieve the purpose of extinction;
- Using extinction additives (matting agent, or matting curing agent);
- Using a synergistic combination of the above-mentioned three kinds of methods.
The above methods generally reduce the film gloss of 40 to 70 gloss units, namely the formation of the film the final gloss is about 20 to 30, the lower the gloss requirement difficult to achieve.
In recent years the advent of low light acrylic resins for powder coating, My company uses this new type of resin as a key material, by a large number of test studies, the successful production of the good weather resistance, matt acrylic coating gloss can be as low as 5 below powder coating; and has a large number of supply market, the majority of users spoke highly of.
Temperature curing acrylic resin, polyester resin cross-linking reaction of the carboxyl functional groups (epoxy) to form a network structure, the coating surface showing micro uneven micro irregularity surface a light scattering effect, so as to achieve the effect of extinction.
Weather resistance and light outdoor powder coating as a user can accept only the most basic requirements, should also have other properties, such as loose, storage stability, mechanical strength (impact strength, flexibility, hardness) and so on. An important guarantee of formulation research and design of coating performance and quality. Above us one by one in-depth and meticulous research.
Loose paint, resin characteristics and the choice of particle size distribution, the choice of the additives added, fill the selection to be addressed.
The storage stability of the coating and resin characteristics, particle size distribution have a great relationship. As we all know, the resin softening point (or glass transition temperature) is too low, the powder coating is easy to agglomerate. Powder of particle size too small and easy to agglomerate in storage. To solve this problem, in addition to resin selection and particle size distribution to be adjusted, you can also add some additives.
The mechanical strength is an important performance of powder coating. In fact, the mechanical properties of the powder coating is the combined result of several factors. Milling technology and coating technology coatings affect the mechanical properties of the substrate pretreatment prior to coating, the coating curing process conditions will not go into details.
Milling technology, raw materials and formulation design is the key.
The powder coating raw materials which the resin is the most important. Some resin from the technical indicators to meet the requirements, but its low reactivity, it is difficult in the curing conditions, we are asking for a complete response. The formation of coating mechanical strength is not high. Pigment formulations, packing some too strong alkaline, it will consume the part of the carboxyl group of the resin, the cured coating reaction, leading to film the final mechanical strength. In our experiments during the study also found that the lower number of materials of coating mechanical properties, due to limited conditions, we also difficult theory to explain.
The pigment to binder in the well-known formula than improper, the excessive content of pigments and fillers, coating mechanical properties will be reduced, therefore Zhigu to reduce product costs more is not desirable to fill regardless of the film properties. The appropriate application of additives to promote the curing reaction completely, or add a toughening agent, can improve the mechanical strength of the coating.
The coating of orange peel phenomenon is a problem worth exploring. The orange peel is a feature of the powder coating. The powder coating industry in China (especially users of the powder coating) exists in this have a misunderstanding, that is too much emphasis on the orange peel, orange peel is the film quality is not good, the outside is now poor. A typical example is the aluminum ceiling with powder coating paint, many customers of the application areas of the appearance of the coating to ask too much, in fact, high above the ceiling surface with a slight orange peel is not impact outside now and decorative effect. There is always the duality of things, the fish can not have both, a benefit must be a disadvantage. Excessive leveling course, orange peel on the Elimination of film, but often at the expense of other properties of the coating. Therefore focus only on the coating of orange peel, rather than focus on the idea of the quality of the coating to be changed. Our view is that the Office should not affect the appearance of the coating, moderate orange peel allowed. Orange peel by no means equal to poor quality does not mean that the appearance of bad. In general situations, mild to moderate orange peel does not affect the decorative, is perfectly acceptable. Of course, we have many ways to make the orange peel effect down to the very low level. The orange peel is a myth that many in the industry believe that the leveling agent is to increase the flow and leveling, reduce the orange peel. However, the study results tell us that by increasing the amount of leveling agent to improve leveling, reduce the orange peel effect is negligible, the leveling agent’s fundamental role is to eliminate shrinkage. Leveling agents reduce excessive make-coated mechanical strength, resulting in a series of film ills.
Matt powder coating gloss issues are also worth exploring. The so-called light and do not have a strict definition, it was considered that the gloss below 15 units can be regarded as light; some 10 or below 5 is considered the real matt. The gloss level of user can be decorative requirements according to their own products, powder coating, production department, the key is to meet the requirements of the user of this. Acrylic matt powder coating test, we gloss as an important research content. The amount of acrylic resin is the key, use the more shiny, the lower; the amount of as little more luster higher, the reason is obvious. The saying goes, led to launch the body to changes in the coating gloss also ensure that other film properties unchanged, is indeed not an easy thing to adjust the proportion of various ingredients, if necessary, add some special additives. Formula design is correct, we can take care of all aspects of performance requirements. After a thorough study, we have been able to in the coating gloss adjustable between 2 and 35. Such a wide range of gloss should be able to meet a variety of decorative need.
Acrylic matt powder coating in China is still an emerging field, over time, this species will increasingly improved. Greater development in the near future, the acrylic powder coating.