As time goes on, the gloss of the coating film will gradually decrease, which is generally called gloss loss. During the atmospheric aging test, the degree of gloss loss of the sample can be measured with a DFH-66l photoelectric gloss meter, expressed as a percentage of gloss loss (compared with the original gloss of the paint film), and its grades can be divided into five categories:
O level No loss of gloss, loss rate is less than 5%;
Level 1 Slight loss of light, loss rate of 6%~3o%;
Level 2 Obvious loss of light, the rate of loss of light is 31%~6o%;
Grade 3 Severe loss of gloss, the rate of loss of light is 61%~9o%;
Grade 4 completely loses light, and the light loss rate is above 91%.
