1.What are the principles and applicable scenarios of the pencil hardness method?
Principle: Use pencils of different hardness levels (from the softest 6B to the hardest 9H) to scratch the coating surface under a specific pressure, and determine the hardness level by whether the coating is scratched.
Applicable scenarios: Applicable to color-coated coils with thin thickness (usually ≤50μm), such as home appliance panels and color-coated coils for interior decoration. It is the most commonly used rapid detection method in the industry.
2.What are the principles and applicable scenarios of the Shore hardness method?
Principle: The pressure needle of the hardness tester penetrates the coating surface under a specific pressure, and the hardness value is converted into two types according to the depth of penetration: Shore A (soft material) and Shore D (hard material).
Applicable scenarios: Suitable for thicker (usually > 50μm) or more elastic coatings, such as some PVC coated color coated coils and elastic topcoat coatings.
3.What are the applicable scenarios for Knoop hardness test and Vickers hardness test?
Principle: Both are microhardness tests. Diamond indenters are used to indent the coating surface under a specific load, measure the diagonal length of the indentation, and calculate the hardness value (unit: HK or HV).
Knoop hardness: The indenter is a diamond-shaped quadrangular pyramid, and the indentation is slender, suitable for thin coatings (<20μm), with little damage to the coating;
Vickers hardness: The indenter is a square quadrangular pyramid, and the indentation is symmetrical, suitable for medium-thick coatings (20-100μm).
4.What are the principles and applicable scenarios of the pendulum hardness method?
Principle: The hardness is evaluated by the energy decay rate of the pendulum when it swings on the coating surface. The bottom of the pendulum contacts the coating. The higher the hardness, the slower the pendulum swing decays and the more times it swings.
Applicable scenarios: Mainly used to evaluate the comprehensive performance of elasticity and hardness of the coating, suitable for thicker organic coatings (such as color-coated roll topcoats for building exterior walls).
5.What are the different characteristics of different methods?
Pencil hardness method: simple operation, low cost, qualitative evaluation of scratches
Shore hardness test: portable and suitable for rapid on-site testing
Vickers/Knoop hardness: high precision, quantifiable, requires microscopic observation
Pendulum hardness method: reflects the comprehensive performance of coating elasticity and hardness