1.What properties does the scratch resistance of a coating depend on?
Coating Hardness: The ability to resist indentation or scratches from hard objects.
Coating Toughness: The ability to resist cracking and peeling.
Coating Adhesion to Substrate: Whether the coating peels off completely when scratched.
Surface Lubricity: Smooth surfaces are less prone to scratches.
2.What are the principles and procedures for testing pencil hardness?
Principle: A series of pencils of known hardness (from the softest 6B to the hardest 9H) are used to scratch the coated surface to see if permanent scratches are caused.
"Grade" indicates the highest pencil hardness that the test can pass. For example:
Ordinary polyester coating: Typically F ~ H.
High-quality polyester/silicone-modified polyester: Can reach H ~ 2H.
PVDF (fluorocarbon) coating: Typically in the H ~ 3H range, benefiting from its excellent toughness and hardness.
High abrasion-resistant special coatings (such as abrasion-resistant polyester, plastisol): May reach 2H ~ 4H+, but excessive hardness may sacrifice flexibility.
Note: Pencil hardness is an important indicator for evaluating scratch resistance, but not the only one.
3.What are the principles and grade representations of the Taber abrasion resistance test / drop test?
Principle: The coating surface is rubbed with standard abrasives (such as grinding wheels or gravel) under specified pressure and speed.
"Grade" indicates: This typically reports the number of cycles required to wear down a certain thickness of coating, or the mass loss (mg) after a specific number of cycles. Higher values indicate better abrasion/scratch resistance.
4.What are the principles and ratings of abrasion resistance testing?
Standard: Commonly used for appliance panels.
Principle: Rubbing the coated surface back and forth with a paper strip of a specific material.
"Grade" indicates the number of rubs required before the substrate shows visible scratches. High-quality appliance panels require hundreds of rubs or more.
5.How do I obtain or specify the "level" I need?
Consult material standards or technical data sheets:
Request detailed TDS from the color-coated coil manufacturer. These typically list key physical properties such as pencil hardness, abrasion resistance (Tabè value), and adhesion grade.
Select products and standards based on end-use:
Architectural roofing/wall panels: Focus on adhesion, flexibility (T-bend), and long-term weather resistance; a pencil hardness of around H grade is generally acceptable.
Appliance panels (e.g., refrigerators, washing machines): Require extremely high surface scratch and abrasion resistance; usually specifies strict pencil hardness (≥2H) and RCA abrasion cycles.
Metal furniture/interior decoration: Requires good feel and resistance to everyday scratches; pencil hardness and appearance are equally important.
Food and beverage cans, containers: Scratch and abrasion resistance are basic requirements, combined with chemical resistance and corrosion resistance.