涂膜的成膜过程
Film forming process of film
涂料涂刷在物体表面上后，通过溶剂的挥发而固化成膜（针对溶剂型涂料而言）。涂料涂膜的形成过程对涂膜的表面粗糙程度和光泽至关重要。在湿膜阶段，溶剂的挥发速率受溶剂在涂膜表面的扩散控制，当溶剂的各组分挥发速率差别不大时，有可能得到高光泽的表面；反之，当溶剂的各组分在湿膜阶段的挥发速率不相同时，它会使聚合物分子倾向于形成卷曲，甚至析出，变成大小不一的颗粒或团状物，涂膜表面呈现出凹凸不平。在干膜阶段，溶剂的挥发速率主要受溶剂在涂抹整体里的扩散控制，也会对涂膜表面的粗糙程度产生影响。此外，在涂膜的形成过程中，随溶剂的挥发，涂膜会变薄并收缩，涂料中的一些悬浮的重粒子就会在涂膜表面重新排列，造成涂膜表面的不平整。
After the coating is applied on the surface of the object, the film is solidified by the volatilization of the solvent (for solvent based coating). The formation process of coating film is very important to the surface roughness and gloss of coating film. In the wet film stage, the evaporation rate of the solvent is controlled by the diffusion of the solvent on the surface of the film. When the evaporation rate of each component of the solvent is not very different, it is possible to obtain a high gloss surface; on the contrary, when the evaporation rate of each component of the solvent is different in the wet film stage, it will make the polymer molecules tend to form curls, or even precipitate into particles or clusters of different sizes. The coating surface is uneven. In the dry film stage, the volatilization rate of solvent is mainly controlled by the diffusion of solvent in the whole coating, and also affects the roughness of the coating surface. In addition, in the process of film formation, with the volatilization of solvent, the film will become thinner and shrink, and some suspended heavy particles in the coating will rearrange on the surface of the film, resulting in the uneven surface of the film.