1.What about the core optimization of coating materials?
Silicon modified polyester (SMP): By introducing silicon oxygen bonds (Si-O) to improve heat resistance, the long-term temperature resistance can reach 200~250℃, the short-term temperature resistance can reach 300℃, and it is not easy to turn yellow at high temperature (silicon can inhibit oxidation reaction), suitable for medium and high temperature scenes (such as oven shell, industrial pipeline).
Fluorocarbon resin (PVDF/FEVE): The fluorine-containing group (C-F bond) has high bond energy, extremely strong chemical stability, long-term temperature resistance of 200~260℃, and excellent UV resistance and oxidation resistance. It is suitable for high temperature + outdoor exposure scenes (such as roofs, high-temperature workshop exterior walls), but the cost is relatively high.
Polyimide (PI): High-end high-temperature resistant resin, long-term temperature resistance can reach more than 300℃, short-term temperature resistance can reach 500℃, suitable for extreme high temperature scenes (such as metallurgy, chemical high-temperature equipment), but the process is complex and the cost is high, and it is only used for special needs.
Avoid using ordinary polyester (PE) or epoxy resin: Ordinary PE has a long-term temperature resistance of only 120°C, and its molecular chains are prone to breakage at high temperatures, causing the coating to turn yellow and lose its gloss.
2.How do pigments and fillers enhance heat stability?
Pigment selection:
Inorganic pigments (such as titanium dioxide, iron oxide red, chrome yellow, cobalt blue, etc.) are preferred, as they have high chemical stability and can withstand temperatures of 300~800℃ (organic pigments are mostly resistant to temperatures below 150℃ and are prone to decomposition and fading).
For special colors (such as bright colors), high-temperature resistant organic pigments (such as quinacridones, which can withstand temperatures of 200~250℃) can be used, and low-temperature resistant pigments such as azo pigments can be avoided.
Filler optimization: Adding inert fillers such as mica powder, ceramic microbeads, and silica (SiO₂) can enhance the density of the coating, reduce the damage to the resin caused by heat conduction, and inhibit the migration and oxidation of pigments at high temperatures.
3.How to improve heat-resistant auxiliary performance through additives?
By adding functional additives, the weak links of the coating at high temperatures can be compensated:
Heat stabilizers: such as organic tin and metal soaps, which inhibit the decarboxylation and chain breaking reactions of the resin at high temperatures; for fluorocarbon systems, fluoride stabilizers can be added to prevent fluorine atoms from falling off.
Antioxidants: such as hindered phenols and phosphites, which capture free radicals generated at high temperatures and delay the oxidation and yellowing of the coating (especially in the "high temperature + oxygen" environment).
Ultraviolet absorbers (UVA) and hindered amine light stabilizers (HALS): for outdoor high temperature scenes, reduce the degradation of the coating caused by the synergistic effect of "high temperature + ultraviolet rays".
4.How to improve coating density through coating and curing process?
Coating thickness and uniformity:
Coating thickness should be moderate: too thin coating is prone to rapid aging due to high temperature; too thick coating may cause residual solvent due to incomplete curing, which will be released at high temperature, resulting in blistering and discoloration of the coating.
Roller coating or electrostatic spraying process is used to ensure uniform coating and avoid local thinness and heat resistance.
Curing temperature and time:
Use "high temperature slow baking" process: set curing temperature according to resin type, extend curing time, ensure complete cross-linking of resin, and reduce unreacted groups.
Avoid under-curing or over-curing.
5.How to enhance coating adhesion and corrosion resistance through substrate pretreatment?
Substrate cleaning: Remove oil and scale on the surface of the substrate thoroughly by degreasing and pickling.
Chemical pretreatment: Phosphating and passivation are used to form a conversion film to enhance the adhesion between the substrate and the coating and prevent the coating from falling off at high temperatures.
Substrate selection: For high temperature and high humidity scenes, galvanized substrates or aluminum-zinc-plated substrates are preferred, which have stronger corrosion resistance and can reduce the penetration effect of substrate rust on the coating.