LONGKOU GUOMEI DECORATIVE MATERAIL CO.,LTD
Amy Diao +86 13361390707
ADD:Wenhua Road Beima Town Longkou City Shandong Province,China
Powder Coating is a type of coating that is applied as a free-flowing, dry powder. The main difference between a conventional liquid paint and a powder coating is that the powder coating does not require a solvent to keep the binder and filler parts in a liquid suspension form. The coating is typically applied electrostatically and is then cured under heat to allow it to flow and form a "skin". The powder may be a thermoplasticor a thermoset polymer. It is usually used to create a hard finish that is tougher than conventional paint. Powder coating is mainly used for coating of metals, such as household appliances, aluminum extrusions, drum hardware, and automobile and bicycle parts. Newer technologies allow other materials, such as MDF (medium-density fibreboard), to be powder
Properties of powder coating
Because powder coating does not have a liquid carrier, it can produce thicker coatings than conventional liquid coatings without running or sagging, and powder coating produces minimal appearance differences between horizontally coated surfaces and vertically coated surfaces. Because no carrier fluid evaporates away, the coating process emits few volatile organic compounds(VOC). Finally, several powder colors can be applied before curing them all together, allowing color blending and bleed special effects in a single layer.
While it is relatively easy to apply thick coatings which cure to smooth, texture-free coating, it is not as easy to apply smooth thin films. As the film thickness is reduced, the film becomes more and more orange peeled in texture due to the particle size and glass transition temperature(Tg) of the powder.
Most powder coatings have a particle size in the range of 2 to 50 μ (Microns), a softening temperature Tgaround 80°C, a melting temperature around 150°C, and are cured at around 200°C. for minimum 10 minutes to 15 minutes (exact temperatures and times may depend on the thickness of the item being coated).
For such powder coatings, film build-ups of greater than 50 μ (Microns) may be required to obtain an acceptably smooth film. The surface texture which is considered desirable or acceptable depends on the end product. Many manufacturers actually prefer to have a certain degree of orange peel since it helps to hide metal defects that have occurred during manufacture, and the resulting coating is less prone to showing fingerprints.
There are very specialized operations where powder coatings of less than 30 micrometres or with a Tg below 40°C are used in order to produce smooth thin films. One variation of the dry powder coating process, the Powder Slurry process, combines the advantages of powder coatings and liquid coatings by dispersing very fine powders of 1–5 micrometre particle size into water, which then allows very smooth, low film thickness coatings to be produced.
For garage-scale jobs, small "rattle can" spray paint is less expensive and complex than powder coating. At the professional scale, the capital expense and time required for a powder coat gun, booth and oven are similar to a spray gun system. Powder coatings have a major advantage in that the overspray can be recycled. However, if multiple colors are being sprayed in a single spray booth, this may limit the ability to recycle the overspray.
Advantages of powder coating instead of other coatings
1.Powder coatings contain no solvents and release little or no amount of Volatile Organic Compounds (VOC) into the atmosphere. Thus, there is no longer a need for finishers to buy costly pollution control equipment. Companies can comply more easily and economically with the regulations of the U.S. Environmental Protection Agency.
2.Powder coatings can produce much thicker coatings than conventional liquid coatings without running or sagging.
3.Powder coated items generally have fewer appearance differences between horizontally coated surfaces and vertically coated surfaces than liquid coated items.
4.The wide range of specialty effects are easily accomplished using powder coatings that would be impossible to achieve with other coating processes.
Types of powder coating
There are two main categories of powder coating: thermosets and thermoplastics. The thermosetting variety incorporates a cross-linker into the formulation. When the powder is baked, it reacts with other chemical groups in the powder to polymerize, improving the performance properties. The thermoplastic variety does not undergo any additional actions during the baking process as it flows to form the final coating.
The most common polymers used are polyester, polyurethane, polyester-epoxy(known as hybrid), straight epoxy(fusion bonded epoxy) and acrylics.
1.The polymer granules are mixed with hardener, pigments and other powder ingredients in an industrial mixer, such as a turbomixer
2.The mixture is heated in an extruder
3.The extruded mixture is rolled flat, cooled and broken into small chips
4.The chips are milled and sieved to make a fine powder
The powder coating process
The powder coating process involves three basic steps:
1.Part preparation or the pre-treatment
2.The powder application
According to a market report prepared in August, 2016 by Grand View Research, Inc., the global powder coatings market is expected to reach USD 16.55 billion by 2024. Increasing use of powder coatings for aluminum extrusion used in windows, doorframes, building facades, kitchen, bathroom and electrical fixtures will fuel industry expansion. Rising construction spending in various countries including China, the U.S., Mexico, Qatar, UAE, India, Vietnam, and Singapore will fuel growth over the forecast period. Increasing government support for eco-friendly and economical products will stimulate demand over the forecast period. General industries were the prominent application segment and accounted for 20.7% of the global volume in 2015. Increasing demand for tractors in the U.S., Brazil, Japan, India, and China is expected to augment the use of powder coatings on account of its corrosion protection, excellent outdoor durability, and high-temperature performance. Moreover, growing usage in agricultural equipment, exercise equipment, file drawers, computer cabinets, laptop computers, cell phones, and electronic components will propel industry expansion.