Grinding (GB/T1770-89)
Because in the process of painting, it is always necessary to carry out local grinding and finishing; for the surface of the old paint film painted or putty, it is necessary to carry out effective overall grinding. Therefore, grinding is a required process in the coating process, and the difficulty of grinding directly affects the construction efficiency.
The sandability is generally judged by the degree of sanding or the difficulty of sanding when sanding. If it feels greasy when it is heavily sanded and polished, it will not be easy to polish and smooth, and the polishing performance will be poor. For example, use 300# water sandpaper to polish 30 times to see if it is easy to polish without curling; or use 200# water sandpaper with a weight of 200g to polish it 100 times, and it should be smooth. Generally, hard coating films have better sandability, and soft paint films have poor sandability.
recoatability
Recoatability refers to whether the second coat has problems such as bottoming, bleeding, non-drying and poor adhesion to the bottom layer within the specified interval.
Undercutting, bleeding, and non-drying are usually due to improper use of paint, or too short painting intervals; too long painting intervals or recoating on old paint films are prone to poor bonding.
Therefore, in the case of composite coating systems or multiple coats, recoatability appears to be a very important application performance. Of course, the recoatability can be improved by adjusting the construction process conditions.
