Gloss is the apparent optical property of an object. Surface smooth material will produce directional reflection to another direction when it receives visible light, which is called specular reflection. As a result, the surface of the material is shiny, which is specular luster. The size of its reflection ability is called specular luster. Spend. The color-coated board requires specular gloss measurement not only to ensure the appearance of the coating but also to ensure the durability of the coating.
The gloss of color-coated panels mainly comes from three aspects: substrate, coating and construction process. As the whole process of the color-coated sheet process, the substrate is an objective condition, and the coating is dull, although it is related to the smoothness of the substrate, that is, the gloss of the substrate is cold-rolled sheet is better than that of galvanized sheet, because the smoothness The surface makes it easier for the coating itself to form a specular reflection (one-way reflection) of light. However, since most of the current color-coated substrates are galvanized sheets, when we analyze the influencing factors of gloss, coating and construction technology are the main two possibilities.
In the paint, the type and particle size of the paint affect the gloss of the coating. The pigment particles are thick, the fineness is not enough, the particle gap is large, and the absorption of the paint is also large. The leveling of the coating during construction is poor and cannot Forms a smooth film that makes the product dull. In addition, in terms of construction technology, attention should be paid to the viscosity of the coating on the machine and the curing form of the coating. Excessive viscosity of the coating will make it difficult to peel off the coating roller from the surface of the substrate and reduce the gloss of the coating. Too fast curing speed will easily make the coating Lack of luster.
The specular gloss of the coating of the color-coated plate is determined by measuring the ratio of the reflected luminous flux on the surface of the sample to the incident luminous flux, that is, the light and reflectance to determine the strength of the surface gloss. Usually 60° incident angle is used for measurement. When measuring accuracy, if the 60° gloss value is higher than 70 gloss units, it is better to use 20° incident angle measurement; if the 60° gloss value is lower than 10 gloss units, it is appropriate to use 85° incident angle measurement. , and take the arithmetic mean of the measurement results at 3 different positions on the surface of the sample as the specular gloss of the coating of the sample.
The domestic KGZ system, XGT series, XGP series, WGG series, QZX series and other specular gloss meters (including single-angle and multi-angle, desktop and portable specifications) launched by many manufacturers have been on the market for many years, and the data transmission to a personal computer for graphing or numerical analysis. Some multi-angle gloss meters can display the gloss readings of the coating at 20°, 60° and 80°, which meet the international standards of ISO, ASTM, DIN and BS, and are easy to operate. Figure 4-10a is one of the digital portable mirrors Template for gloss meter.
In addition, according to the information, there are many online specular gloss meters that can be developed abroad and have been widely used (Figure 4-10b). This online gloss meter is usually placed at the exit of the process section of the color coating line. The color-coated plate is 10mm, which is non-contact. At the same time, the instrument is equipped with a continuous reading display screen, so that the operator can detect the gloss of the coating in real time through the logarithm of the display screen at any time, and realize the rapid feedback of process data. Adjust the coating thickness of the roller coater and the temperature of the curing oven at any time.
