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 σ decreased and breaking elongation ε 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.
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