What is Powder Coating?
Powder coating is a type of coating that is the size of a micron, comprised of solid raw materials such as resin, and does not contain any solvents. All powder coating raw materials such as pigments, hardeners, fillers, and additives are in solid form and these materials are homogenized by being mixed together. Now that we know the answer to the question “What is powder coating?”, we can look at the history and areas of use of the powder. Powder coating, which was produced as a safer alternative to liquid paint, was first developed by Dr. Erwin Gemmer in Germany in 1953. With Gemmer’s fluidized bed technique, the particles of powder coatings were attached to the surface. In the following years, epoxy, epoxy-polyester, polyester, and polyurethane powder coatings were produced. Powder coatings, which are frequently preferred across the world, started to be used in Turkey in the 1980s.
Powder coatings, which are ready for use, environmentally friendly, and create a decorative surface, are used in many sectors from architecture, automotive industry, and MDF coating to glass production, ceramic industry, and home appliances.
Types Of Powder Coating
Powder Coatings are divided into various types depending on their areas of use and purpose
The formula contains an epoxy-type resin and a suitable hardener. It is used when resistance against chemicals is desired. Particularly, fuel tanks can be shown as an example. These types of powders have less resistance against heat and light. It is also used as a primer when high corrosion resistance is required.
It contains epoxy and polyester resin. It is a powder type developed to provide physical and chemical resistance properties together. It is used indoors. It is particularly an inevitable solution for the white appliances industry. Moreover, home/office lighting fixtures, metal furniture, hospital equipment, towel warmers, radiators, armatures, and shower cabins can be coated with this type of powder. Although it is stronger than epoxy type powders in terms of heat and light resistance, it has less resistance than outdoor polyester powders which we will discuss later.
- Polyester/TGIC: It contains a polyester resin and TGIC hardener. It is an exterior wall powder. It is especially recommended for aluminum window and door profiles. When properly designed and used, it can withstand sunlight and other climatic conditions for 10 years. It is mainly used in the aluminum profile industry, agricultural machinery, bicycles, rims, lighting fixtures, etc.
- Polyester/Primid: It contains a polyester resin and primid hardener. It is an exterior wall powder. It is used for exterior walls, where loss of color and brightness is undesirable, and especially for architectural applications. It is recommended for aluminum window and door profiles. When applied properly, it can withstand up to 1015 years depending on the climatic conditions like other PT. TGIC-containing products have to receive certain labeling marks according to European Union norms while primid products do not have any marking. PRIMID, which is widely used especially in the European market, is the strongest competitor of TGIC.
Its formula contains a polyester resin and suitable (isocyanate) hardener. It is highly resistant to abrasion, moisture and salt spray test. (Compared to other polyester exterior wall products, it provides chemical resistance as well as UV resistance.) It can be used in automotives, bathroom accessories and garden products.
It is particularly preferred in the automotive industry. These are very strong and durable powders. However, they are not produced in the facilities where other types of powders are produced due to the incompatibility with other types of resins and contamination. Therefore, this product is not included in the Pulver Kimya product range.
Powder Coating Production
The raw materials of powder coating are prepared by weighing according to the formulation.
The raw materials are homogenized using the “dry mixing” technique. This process is carried out using mixers. Different types of mixers can be used depending on different requirements.
The prepared homogeneous mixture is given to the feeding section of hot extruders.
Hot extruders increase the contact of mixed and homogenized raw materials with each other and allow resins to combine with other raw materials. Extruders operate at high temperatures (100°C to 130°C).
After the hot extrusion and homogenization are completed, the powder is extruded in molten form from the extruder and passes through chill rolls.
The powder, which is formed into a thin layer, passes through the cooling belt and cools to room temperature. The cooled material passes under the crusher and is transformed into the chips.
The grinding process is carried out with suitable mills. Powder size is very important for the user. With mills and classifiers, powder sizes can be brought to desired ranges according to use and powder type.
After very fine powders are collected with air, they are passed through suitable filters and cyclones by separating from the air to prevent them from polluting the air.
Coarse powders are also separated from the product using the sieving process.
Powders which are ground and brought to desired sizes are packaged in appropriate weights and presented to the user.
Usage Advantages of Powder Coating
Unlike liquid paints, powder coatings do not contain any solvent substances and consist of mixtures of resins, hardeners, pigments, fillers and additives. There are various application techniques in powder coating. The most common techniques include Electrostatic Coating and Fluidized Bed Coating. The immersing technique enables a thicker coating
During its production and use, powder has fewer negative effects on health compared to wet paint. This has been proven by various studies. In addition, the amount of energy required for the powder to ignite is 100 times higher than liquid-based paints. Therefore, the powder is very difficult to ignite and its lower explosive limit is higher than liquid paints.
The advantages of powder coating can be summarized briefly as follows;
- Powder coating is environmentally friendly. No waste is produced during production and consumption; therefore, it does not cause air or water pollution. In terms of environmental protection, powder coating does not contain the volatile organic compounds (VOC) found in wet paint.
- The amount of energy required for powder to ignite is much higher than liquid paints. Therefore, its lower explosive limit is higher.
- Powder has fewer negative effects on health than other paints. Moreover, it does not cause any problems when in contact with skin.
- Powder is ready to use. It does not require any mixing or dilution with liquid. The gun hose can be inserted into the powder bag and used immediately.
- The powder coating technique is easy to use and the operator can be trained in a very short period. It is very suitable for being used in manual and robotic systems. Thus, the operator can become an expert with brief and practical training.
- All kinds of decorative surfaces can be obtained with powder coating. Surfaces with a e.g. smooth, shiny, rough, sandpaper-like, and varnished appearance can be easily achieved with powder coating.