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 by the DFH-66 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:
No loss of light at level 0 , the rate of loss of light is less than 5%;
Grade 1 slight loss of light, the loss rate is 6%~30%;
Grade 2 obvious loss of light, loss rate 31¾-~60%;
Grade 3 severe loss of light, the loss rate is 61%~90%;
Level 4 completely loses light, and the loss rate is over 91%.
