Kenji Ueki

Influence of Solvent Composition on the Mechanical Properties of Coating Films

This paper deals with the influence of solvent composition upon viscoelastic properties of paint films, The samples of various solvent-diluent ratio in the solvent composition were prepared for typical nitro-cellulose lacquer, typical acrylic lacquer, acid catalyzed melamine alkyd resin paint, alkyd resin paint, polyamide resin cured epoxy resin paint and melamine alkyd resin paint. Viscoelastic properties of the films were determined by the measurements of stress-strain relation and dynamical viscoelasticity. Meanwhile, degree of swelling of the films was measured and also the retained solvent in the films were measured by gas chromatography. Experimental results are summarized as follows. (1) It was generally found for air drying type paint that when the concentration of diluent increased, values for dynamical modulus E and stress 6 decreased and breaking elongation e showed maximun value. Influence of the solvent composition was not found for nitrocellulose lacquer due to the rigidity of the nitrocellulose molecule. (2) Although acid catalyzed melamine-alkyd resin paint gave apparently the similar results as (1), the mechanism is not the same. The main reason is in the difference of the cross-link density of the films. (3) As a rule, viscoelastic properties of baking type paint were not affected with the solvent composition. (4) The results described above were considered from the viewpoint on the state of vehicle polymer in the solution. * Himejima, Nishiyodogawa-ku, Osaka ** Aihara, Sagamihara, Kanagawa

Study of Intercoat Adhesion Failure by Ultrasonic Wave Method

The study was carried out to investigate the over cure of undercoat films which is considered as the one of the causes of intercoat adhesion failure. The paint tested were melamine-alkyd (baking type) and acid catalysed urea resin.The panels were prepared by applying the same type of paint on the undercoat which was cured in various curing degrees. Intercoat adhesion properties were tested by adherometer and cross hatch test which is used widely in paint industry, and the ultrasonic wave method. To summarize the results are as follows ; ( 1 ) The ultrasonic wave method is suitable for the test of adhesion of paint film, especially for intercoat adhesion. ( 2 ) As the cure of the undercoat proceeded, the adhesion with topcoat reduced. This phenomenone is considered as the result of disappearance of active points of adhesion (functional group). ( 3 ) The intercoat adhesion were evaluated for the several combinations of paints on the market. ( 4 ) The mechanism of the adhesion determination method was also considered. Ogawa-Nishimachi, Kodaira-shi, Tokyo.