The performance of the coating is the key index that affects its use effect and durability, among which the measurement method of hiding power, solid content, gloss, freshness and paint film orange peel is particularly important. In this paper, the methods for determining these properties are elaborated in combination with relevant standards and testing practices.
1. Determination of coating hiding power
The hiding power of a coating is the minimum amount (g/m²) that can cover the base color when the paint is evenly applied to the surface of the object. The measurement of the hiding power can be used in the "Paint Hiding Power Measurement Method" method A and B.
Nail method (brush method)
Preparation of black and white lattice glass plates - black and white lattice patterns are prepared on the glass plates, a layer of black nitro paint is sprayed, and parts are peeled off at intervals before white nitro paint is sprayed, and finally 32 black and white square grids are formed.
Brush test
Weigh the sample and paint brush according to the specified viscosity.
The specimen is evenly brushed on the black and white grating.
Put it in a dark box to observe, and record the dosage with just covering the black and white grid.
The hiding power is calculated according to the formula to ensure that the amount of diluent is deducted.
Method B (Spraying Method)
Preparation of black and white checkered wood boards - spray black nitro paint on the wooden board, paste white paper and peel off parts at intervals, and then spray white paint to make 16 black and white checkered boards.
Spray test
A thin layer of the specimen is sprayed on a glass plate.
Place it in a camera obscrama to observe the covering.
Wipe the back and edge of the glass plate, bake to a constant weight, and calculate the hiding power according to the formula.
2. Determination of solid content of coatings
The solids content of a coating is the ratio of the mass of its residue after baking to the mass of the specimen.
Sample preparation - dry Petri dish baking and weighing, take 1.5-2g sample in the Petri dish.
Baking and weighing - Bake the specimen in a constant temperature oven for 30 minutes each time until the difference between the two weighings ≤ 0.01g.
Calculate the solids content – on average and make sure that the difference between the two results is no more than 3%.
3. Detection of paint film gloss
Gloss is an important index to evaluate the light reflection performance of the paint film surface.
Gloss testing standards and equipment
According to the standard "Determination of the Mirror Gloss of Pigment Paints and Varnishes without Metallic Pigments", the test can be performed using the BYK Portable Gloss Meter or the GZ-2 Photoelectric Gloss Meter.
Detection method
Ensure instrument calibration and sample cleanliness.
Select the appropriate detection angle according to the gloss range of the paint film (20° for high gloss, 60° for medium gloss, 85° for low gloss).
Test different points and take the arithmetic mean.
Fourth, the determination of the freshness of the paint film
Freshness is a comprehensive index of the clarity of the object reflected on the surface of the paint film. It is commonly used for measurement with a portable freshness Tester.
Test principle
The light source is irradiated on the surface of the paint film through a reflector, and the clarity of the reflected image is observed. Record the DOI value corresponding to the clearest readable column. Before testing, calibrate the instrument and ensure that the measurement window is completely covered with paint.
5. Determination of paint film orange peel
If there are micro ripples on the surface of the paint film, it will affect the decorative performance, and this phenomenon is called orange peel. The size of the orange peel can be determined by the BYK orange peel Tester.
Test Method:
The light source illuminates the surface of the paint film at a fixed angle, and the reflected light signal is used to evaluate the ripple frequency and intensity.
The Tester records the orange peel value after moving 10 cm on the surface of the paint film.
summary
The determination of coating properties covers several key indicators such as hiding power, solids content, gloss, freshness and orange peel. The decorative and practical properties of coatings can be accurately assessed through standardized inspection methods such as brushing, spraying, gloss meter testing and portable reflectivity Testers. These tests provide a scientific basis for the quality control of coatings, ensuring that they perform as expected in real-world applications.
