Following experiments on dynamic mechanical measurements of melamine-alkyd resin films were made by using the forced vibration method of longitudial deformation ; 1) Relation between the amount of curing agents (melamine resins) for the soya oil modified alkyd resin, and crosslinking density of cured films. 2) Influences of crosslinking density on the viscoelastic properties, the dynamic glass transition temperatures, and the density of sample films. 3) Effects of pigmentation on the viscoelastic properties, and dynamic glass transition temperatures of sample films. A summary of the experimental results is as follows. 1) Crosslinking density, n of the sample films is given by the content, W (expressed in weight percent) of curing agents according to the following relation ; logn=KW-C (where K and C are constants) 2) Dynamic glass transition temperatures, Tg and the density, p of the sample films linearly increase as the contents, W of the curing agents increase, up to the chemical equivalent quantity of curing agents for the alkyd resin ; Tg=K'W+C', p=K “W+C” where K', C', K “and C” are constants. But, at the chemical equivalent points, the gradients of the linear relations changed and other linear relations were obtained. The gradients of the linear relations below the equivalent points show efficiencies of reactions between the alkyd resin and the curing agents, to the increase of Tg and p. On the other hand, in the region where the excess amounts of melamine resins were added, the gradients of these linear relations were related to the self condensation tendencies of melamine resins. 3) Effects of pigmentation on Tg depend on the melamine resin contents of the sample films, when the melamine resin content was small, Tg of the sample films was a little increased by pigmentation with TiO2, but when the chemical equivalent amounts of melamine resins were added to the alkyd resin, such pigmentation effects were not recognized.
Mutual relation between the fine scratches by the feather brush using to remove dust on the auto-mobile bodies and the various properties on the paint films were studied. Melamine-alkyd black enamels which a butylated melamine resin and an alkyd resin were mixed respectively at the solid weight ratio of 7/3, 6/4, 5/5, 4/6, 3/7 and 2/8 were used as model enamels. The enamels were sprayed on glass plates and tin plates, and based 100°, 120°, 140°, 160° and 180°C for 20 minutes. Feather brushing test, various hardness tests, TABER's abration resistance, coefficient of friction, stress-strain properties and swelling properties were measured on sample films. On the model melanine-alkyd enamels, feather brushing scratches had good mutual relation with surface properties of paint films such as abrasion resistance, coefficient of friction, swinging beam hardness, YOUNG'S modulus related to the flexibility, equilibium swelling ratio related to the crosslinking density, and breaking energy of films. Meanwhile, pencil hardness, elongation and percent fraction extracted from paint films had no relation with. On this study, it was become clear that feather brushing scratches of melanine-alkyd paint films had related to the surface properties, stiffness, flexibility and crosslinking density of paint films.