1.What are the baking temperature and characteristics of polyester (PE) coating?
Baking temperature: usually 200℃~230℃
Features: Polyester coating is one of the most commonly used types of color-coated coils, with good weather resistance and processability. The baking temperature must meet the resin cross-linking reaction (such as the reaction between polyester and curing agent). Too low a temperature will lead to incomplete curing (poor coating adhesion, insufficient hardness), while too high a temperature may cause resin decomposition (discoloration, increased brittleness).
2.What are the characteristics and baking temperature of silicone modified polyester (SMP) coating?
Baking temperature: about 220℃~250℃
Features: SMP coating introduces silicon elements on the basis of polyester, which improves weather resistance and heat resistance, and is suitable for long-term outdoor exposure scenes (such as building roof panels). Higher baking temperature can promote the cross-linking of silicone resin and polyester, and enhance the UV resistance and temperature resistance of the coating.
3.What are the baking temperatures and characteristics of polyvinylidene fluoride (PVDF, fluorocarbon coating)?
Baking temperature: usually 230℃~260℃
Features: PVDF coating has excellent weather resistance, chemical resistance and anti-fading properties, and is a representative of high-end color-coated coils (such as curtain walls, high-end buildings). Its baking needs to reach the melting cross-linking temperature of the fluororesin to ensure the adhesion and long-term stability of the coating and primer, and the temperature control accuracy is required to be high (the deviation needs to be controlled within ±5℃).
4.What other factors affect baking temperature?
Baking time:
Temperature and time are in a synergistic relationship. Baking time can be shortened at high temperature (such as 30~60 seconds at 260℃), and extended at low temperature (such as 1~2 minutes at 200℃). It needs to be adjusted according to the production line speed (usually 30~100 meters/minute) to ensure that the coating is fully cured.
Coating thickness:
Thick coatings (such as dry film thickness > 30μm) require slightly higher temperatures or longer times to avoid incomplete internal curing; thin coatings can be appropriately lowered to prevent over-baking of the surface.
Substrate type:
The thermal conductivity of substrates such as galvanized sheet, cold-rolled sheet, and aluminum sheet is different, and the baking temperature needs to be fine-tuned (such as aluminum sheet heats up quickly, so a slightly higher temperature may be required).
Environmental requirements:
Low VOC (volatile organic compound) coatings may use low-temperature curing formulas, and the baking temperature can be reduced to 160℃~180℃ to reduce energy consumption and exhaust emissions.
5.What is the core purpose of baking?
The essence of coating baking is to use high temperature to induce cross-linking reaction between the resin and curing agent in the coating (forming a three-dimensional network structure), while evaporating the solvent, and finally giving the coating key properties such as hardness, adhesion, and corrosion resistance. Insufficient temperature will lead to "under-curing" (the coating becomes soft and easy to scratch), while too high temperature will lead to "over-curing" (the coating becomes brittle, discolored, and adhesion decreases), so it needs to be strictly controlled within the process range.