Microscopical Study on Organic Coatings (I)

Abstract

Films of pigmented organic coatings were examined by optical and electron microscope. In the preliminary study, lacquer enamels were examined. It was observed that, the pigment particles were not evenly distributed. Some of them were dispersed to single particles, while large part of them formed pigment masses. Bright centers were observed in the certain masses. They are as bright as the area where no substance exists. It is suggested that some of the pigment particles have not been wetted by the vehicle. Many projects were observed on the top surface of the lacquer film. In the course of the weathering test, at first, the projects disappeared and the cavities appeared. Then number of cavities increased one ater another The projects and the cavities are as large as the pigment masses above. mentioned. On the top surface of the film the breakdown is thought to occur at the pigment mass. Electron microscopical crack was not observed, wbieh has been expected to see on the top surface.
The observed specimens are as follows
(1) Ultra-thin film of lacquer enamels-The ultra-thin film of lacquer enamel was : formed on the gelatine precoated slide glass, the gelatine was dissolved in water, then the specimen was obtained.
(2) Ultra-thin section of lacquer films-The lacquer film was made by the common method, and was embedded in wax, then was cut by ultra-microtome.
(3) Replica of sectional surface of lacquer films (chromiun shadowed methocel-collodion replica).
(4) Replica of weathered surface of lacquer films (Ditto).
(5) Thin film of lacquer enamel on slide glass.