With the widespread application of powder coatings in construction, home appliances, industry and other fields, its weather resistance has gradually become the focus of the industry. This paper explores the aging mechanism of powder coatings in the natural environment, analyzes the internal and external factors affecting its weather resistance, and proposes effective methods to improve the weather resistance of powder coatings by using light stabilizers, antioxidants, and optimizing formulations.
I. Main Factors
Weather resistance depends on internal formulation factors (resin, curing agent, pigments and fillers, additives) and external conditions (ultraviolet radiation, atmospheric oxidation, humidity, acid rain, temperature cycle, industrial pollutants).
Among them, ultraviolet rays are the main driving factor for degradation, oxygen accelerates oxidation and free radical chain scission; moisture and heat promote photooxidation; pollutants such as polycyclic aromatic hydrocarbons and ozone act as sensitizers.
II. Technical Approaches
(1) Selection Of Resin And Curing System
Polyester/TGIC: excellent weather resistance and heat resistance; TGIC has toxicity/genotoxicity issues.
Polyester fiber/Primid: non-toxic and storage stable, but easy to yellow/produce pinholes.
Acrylic fiber: high transparency, bright colors, high gloss; high cost, poor toughness.
Polyurethane: full film formation, high adhesion/mechanical strength; there is an isocyanate odor during the curing process.
Fluorocarbon resin: has the best UV resistance/acid rain resistance/chemical corrosion resistance and self-cleaning function; low gloss, poor dispersibility, high baking properties. [Fluorocarbon coatings: characteristics, applications and advantages]
The choice of resin is the core factor that determines weather resistance; choosing the right curing agent is crucial.
(2) Use Of Light Stabilizers And Antioxidants
Benzophenone/benzotriazole UV absorbers (290-400 nm), nickel quenchers, hindered amine light stabilizers (HALS), free radical scavengers and light-shielding pigments (TiO₂, ZnO) have a synergistic effect. Antioxidants include hindered phenols (chain terminators) and phosphites (preventatives); color stability, compatibility, and heat resistance must be considered when selecting.
(3) Formulation Optimization
Avoid the use of raw materials that promote the formation of free radicals; use light-shielding fillers (carbon black, TiO₂, ZnO, CaCO₃, BaSO₄); design a synergistic stabilizer combination; for light-colored products, UV absorbers can be combined with antioxidants to inhibit yellowing.
III. Powder Coating Weathering Test Method
Natural exposure: 45° panel facing south, about 30 days, evaluate gloss, ΔE, and chalking.
QUV accelerated aging: UVA-340 cycle, for example 150 hours (UV 60°C 4 hours/condensation 50°C 4 hours/spraying 3 minutes) to reproduce fading, cracking, and strength loss. [Powder Coating Color Measurement and Variance Control]
Heat Resistance (Anti-Yellowing): Bake at 230°C for 30 minutes.
Conclusion: Panels with added light stabilizers exhibited better gloss/color retention; a combination of UV absorbers and antioxidants was most effective; improving heat resistance may require the addition of anti-yellowing additives.
