The first necessary condition for aging or photochemical reaction of color coated plate is that the surface components of color coated plate can absorb radiation energy; Secondly, when the radiation energy absorbed by molecules is greater than the molecular bond energy, the color coated plate coating can be degraded. The shorter the wavelength of light, the higher the energy it contains.
According to the above theory, the aging of color coated plates in the atmospheric environment is caused by the coating molecules absorbing the energy in the ultraviolet light band higher than its molecular bond energy in the sunlight, leading to the degradation of the coating molecules. With the aging of the coating film, the base material body is gradually lost, and the coating surface becomes rough and lusterless. This loss of Z of the base material will eventually leave more stable pigment particles, which will remain on the surface of the film in the form of unbonded powder. This process is called pulverization.
To sum up, polyester color coated boards with different coating thicknesses have great differences in aging resistance. Thin coating color coated boards have poor aging resistance, while coatings with normal thickness have relatively good aging resistance.
Therefore, it is not feasible to reduce the production cost of color coated plate by reducing the thickness of the coating, which will inevitably lead to serious quality problems. At the same time, it also demonstrates the necessity of clearly indicating the coating thickness in the order contract of foreign color coated plate importers from the side.
