Definition
The paint film scratch resistance tester is a special inspection equipment used to evaluate the resistance of coating surfaces to mechanical scratches. It quantifies the scratch resistance of coatings by simulating scratch behavior under specific conditions, providing key data for material durability evaluation.
How it works:
The instrument is usually based on the principle of scratch testing under controlled loads. The core components include a dicing needle (typically a spherical or tapered tip) that applies precise vertical loading, and a drive stage that allows the sample to move horizontally. During the test, the scribing needle is scratched on the surface of the coating at a constant speed to characterize scratch resistance by measuring the morphology or critical load of the scratch. Its mechanical model can be simplified to:
FN = P / A
where FNis the normal stress, P is the applied vertical load, and A is the effective contact area between the scribing needle and the coating.
Measurement method
Common measurement methods include progressive load method and constant load method. The progressive loading method increases the vertical load linearly during the test process, and the critical load is detected by optical or acoustic sensors when the coating has obvious failure (e.g., cracking, peeling). The constant load rule involves scratching under a fixed load, followed by a microscope or profiler to measure the width, depth, or volume of the scratch, and grade or quantify it according to relevant standards (e.g., ISO 1518, ASTM D5178).
Influencing factors
Test results are influenced by a variety of factors. The instrument parameters include the material of the scribing needle and the radius of curvature of the tip, the load accuracy, the scratching speed and the control of ambient temperature and humidity. Coating properties involve thickness, hardness, modulus of elasticity, and bonding to the substrate. The rigidity of the substrate can also affect the stress distribution. Therefore, the test needs to be performed under standardized conditions to ensure data comparability.
Applications:
The instrument is widely used in industries such as automobiles, furniture, electronics, and building materials. In the automotive field, it is used to evaluate the scratch resistance of body coatings and interior parts. In furniture manufacturing, the durability of wood paints or metal coatings is tested. Shell coatings for consumer electronics and decorative and protective coatings in building materials are also often used for quality control and R&D improvement through such equipment.
Key points of selection
Testing requirements and standard compliance should be considered when selecting. First, the size, shape, load range, scratching speed and other parameters required by the test standard are clarified. The instrument should have good load accuracy and motion control stability. The data acquisition system needs to be compatible with the required measurement methods (e.g., optical observation, friction coefficient recording). In addition, the ease of use of the operating software, the scalability of the equipment (e.g. environmental modules) and after-sales service support are also important considerations.