Powder coating

1. Background and Market Need

Low-temperature curing powder coatings (120–140 ℃) offer significant energy savings and can be cured on sensitive substrates such as MDF (medium-density fiberboard), making them ideal for furniture applications. Meanwhile, the household appliance industry favors these coatings for their matte finish and cost-efficiency.

Traditional epoxy systems offer reliable curing performance, but can present yellowing and low hardness issues. Developing effective formulations under low-temperature conditions is key to expanding their application.

2. Experimental Framework

2.1 Raw Materials: Low-viscosity epoxy resins, dicyandiamide curing agents, and matte additives were selected for experimentation.

2.2 Equipment: Twin-screw extruders, infrared curing ovens, and gloss meters were used to produce and evaluate the powder coatings.

2.3 Testing Standards: Coatings were evaluated based on surface gloss, mechanical strength, impact resistance, and yellowing via colorimetric analysis.

3. Results and Analysis

3.1 Influence of Catalyst Content

Different catalyst dosages significantly affected gloss and flow leveling. At <1% catalyst, gloss improved moderately. At 1.5–2.0%, gloss exceeded 50–55 but surface flow deteriorated. This indicates higher catalyst levels accelerate curing, leading to uneven film formation.

Color difference analysis (ΔE < 0.5) between 130 ℃ and 160 ℃ cured samples showed minimal yellowing, validating the color stability of the epoxy-dicyandiamide system.

3.2 Influence of Epoxy Resin Equivalent

Lower epoxy equivalent resins increased reactivity and cross-linking density. This resulted in better impact resistance and reduced gel time. Thus, choosing low-equivalent epoxy resins can improve overall mechanical performance, though formulation balance must consider storage stability and appearance.

4. Conclusion

• Catalyst Concentration: Increasing catalyst content enhances curing rate and gloss but may compromise flow.

• Yellowing Resistance: Minimal color change between varying cure conditions confirms suitability for visual applications.

• Resin Selection: Lower equivalent epoxy resins improve hardness and impact strength, ideal for high-performance matte coatings.

With advancements in resin design and formulation techniques, low-temperature matte powder coatings will play a vital role in sustainable indoor applications, particularly for furniture and appliances.