THE LEVELING OF THERMOSETTING WATERBORNE COATINGS .1. OBSERVATION OF LEVELING PROCESS

A modified observation system for the leveling process of a coated fluid is proposed, and the observation results are presented and compared with previous results. For the thermosetting waterborne coatings, the theory of Orchard, et al., and ones based on it are not applicable and fail to give even a qualitative description. The theory of Overdiep was found to be reasonable. However, it was tnsufficient to predict the leveling performances of coatings without experimentation. Qualitatively, the original theory suggests the possibility of the reappearance of surface ripples, in other words, the occurrence of the negative amplitude in the surface ripples during the course of leveling, although little data were presented regarding the phenomenon. It was found here that added co-solvent plays an important role on the leveling rate and also the occurrence and the control of the negative amplitude of the surface ripples. These are thought to relate closely to the volatility of the co-solvent and the composition of the solvent residue in the coated film during the leveling process.