Paint drying is to transfer wet paint to solid state. Paint or coating drying is a crucial process after precise spraying. If the paint is not properly cured in right condition, the paint layer can not stick to object or even lead to pollution to other components after assembled. In this article we provide general guides how to select a suitable drying device and introduce the current popular curing technologies.
As we know, different paints are produced by different chemicals, some are solvent based and some are water based. Thus, the different rate components result in different drying conditions. Some paints can be fast dry in room temperature without any device, but some paints require extremely high temperature in a precise furnace. Generally, paints are categorized in liquid and powder coating. Here we mainly introduce liquid paints and its drying conditions.
Liquid Paint Guide
Liquid paints vary a lot due to the different components rate and pigments mixing. However their main component is all based resin which is up to 80% for some paint production. So most paint drying is thermal based under different temperatures. Depends the pigment rate and properties, we might use IR or curing furnace. Normally liquid paints are devided into two categories – Plastic paint and Metal paint. For drying temperature under 100 degrees, we generally put it into plastic category, upper drying temperature are placed in metal category.
Plastic paint – refers to all paints that are suitable for plastic painting purpose(available as PU, ABS etc). Because plastic can not work with high temperature, so all plastic paints are drying under 100 degrees. The drying time depends the production technique and vary a lot, normally PU paint takes longer time in oven (up to 2 hours) while other plastic paint can dry up in shorter time.
Metal paint – works for hardware objects and mostly for engineering purpose. Due to the working environment of such products, the paint has to be durable with some special phycical properties. For example the PTFE teflon coating, it’s nonstick and works with high temperature, thus it’s curing temperaure is up to 450 degrees. For pocerlain and enamel paint, the curing is up to 1000 degrees temperature.
Either for plastic or metal paint, it’s available for both solvent and water base production. Generally, solvent based paint is easier for application and paint shop construction is more flexible. Water based paint is always for high grade application at the moment such as automotive industry and electric components. Water base paint is very sensitive with temperature and humidity so paint shop is always constructed with air conditioning system. The biggest advantage of water base paint is its eco friendly feature as it’s easy cleaning and treatment, no hazard gas pollution and safe to operator etc.
There’s a special liquid paint which is different from all above called UV paint. Instead of traditional thermal, UV curing is based on uv light which is produced from high energy uv lamp. The process is almost instant due to the photo initiator. UV paint is used for almost all type coating solutions for varnishing purpose. It’s fast drying feature makes it ideal choice for mass production.
For all type liquid paint drying /curing, the general process is followed by this logic: leveling then IR or furnace curing or UV curing. After paint spraying, the paint is not always so smooth on object surface due to spray gun setting or different pressures etc. Leveling is to let the paint staying for few minutes, during this process the paint will slightly flow and make the thickness equal. Thus after drying, the surface will be pretty smooth.
Powder Coating
Powder coating is a relative term comparing to liquid paint. It’s available as solid powder and sprayed by electrostatic powder spray gun. So for it’s specific property, powder coating is quite different than liquid paint. Powder coating can be sticky on object not because of pressurised spray but by electrostatic electric absoption. Once it’s cured, it will produce a solid and high grade hardness paint layer for supreme protection. Because it’s electrostatic based and curing under high temperature (180-220 degrees), powder coating can be only used for hardware products.
Also, because its solid powder, it’s easier for paint shop construction. no clean room required and no air conditioning needed. The extra sprayed powder can be fully recycled for reuse. Thus it’s 100% eco friendly. Some high quality powder coating can perfectly replace liquid paint in hardware coating industry for same or even better surface treatment.
