1.How does coating type and composition affect scratch resistance?
Polyester (PE) coating: Conventional polyester coating has medium hardness and average scratch resistance, and is suitable for dry environments without frequent friction.
Fluorocarbon (PVDF) coating: Fluorine-containing resin has a stable structure, high hardness, and excellent wear resistance and impact resistance. Its scratch resistance is better than ordinary polyester, and it is suitable for outdoor curtain walls, vehicle shells and other scenes.
Silicon-modified polyester (SMP) coating: It combines the characteristics of polyester and silicon, with a hardness of about 3H and a scratch resistance between PE and PVDF. It is often used in outdoor buildings.
High weather-resistant polyester (HDP) coating: The hardness and wear resistance are improved by additives, and the scratch resistance is close to SMP, with a higher cost-effectiveness than PVDF.
Inorganic coating: It has extremely high hardness and the best scratch resistance, but it is brittle and easy to crack under impact, which is suitable for special industrial scenes.
2.How does coating thickness and number of layers affect scratch resistance?
Coating thickness: Usually the total thickness of primer + topcoat is 5-25μm. Increasing thickness can improve scratch resistance, but too thick may lead to reduced flexibility and easy peeling.
Multi-layer structure: Some high-end color-coated coils adopt a three-layer structure of "primer + topcoat + clearcoat". The clearcoat layer can provide additional wear protection and further enhance scratch resistance.
3.How does surface treatment affect scratch resistance?
Curing temperature: High-temperature curing can make the coating molecules more closely cross-linked, and improve hardness and wear resistance; low-temperature curing coatings have looser structures and poorer scratch resistance.
Surface texture: Matte, orange peel and other concave and convex surfaces are more scratch-resistant than smooth mirror surfaces. Although mirror coatings are beautiful, they are clearly visible with a slight scratch.
4.What are the test methods and standards for scratch resistance?
Pencil hardness test
Principle: Use pencils of different hardness to scratch the coating surface with a certain force to observe whether scratches are produced.
Judgment: The highest hardness pencil grade that does not produce scratches is the coating hardness. The higher the grade, the better the scratch resistance.
Scratch resistance test
Principle: Use a probe of a specific shape to apply a gradually increasing force to the coating surface and record the minimum force value at which the coating is scratched.
Significance: The greater the force value, the stronger the scratch resistance.
Wear test
Principle: Use a grinding wheel or sandpaper to rub the coating surface for a certain number of times, and evaluate the wear resistance by weight loss rate or appearance change.
Result: The smaller the wear amount, the stronger the coating's ability to resist friction and scratches.
5.What are the precautions in practical application?
Scene adaptation
High friction environments require PVDF, HDP and other coatings with excellent scratch resistance;
Ordinary polyester coatings can be used in low friction environments to reduce costs.
Construction and maintenance
Avoid collision and dragging with hard objects during transportation and installation, and cover with a protective film to reduce scratches;
Use a soft cloth or sponge for daily cleaning, and avoid friction with hard objects such as steel wool and sandpaper.
Limitations
Scratch resistance and impact resistance may conflict, and performance needs to be balanced according to the scene;
After long-term outdoor use, the coating may decrease in hardness and scratch resistance due to aging.