The strength of intercoat adhesion of ten coating systems was measured by pencil test, spiral cut, Adherometer and ultrasonic wave test. In order to analyze the experimental results, stress-strain properties and swelling of paint films in water and mineral spirit were investigated. Main results were as follows : (1) Any relation between paint films properties and intercoat adhesion was not observed in the coating systems. (2) The intercoat adhesion between two solvent type paints (for example NC lacquer and vinyl) was not so good as it has been regarded generally. The latter result showed that intercoat adhesion was influenced by compatibility of the vehicle polymers.
Alcohol treatment of alumina hydrate, such as hydrargillite or boehmite, was performed by reflux method using high boiling point solvents, and changes of structure and surface properties owing to the treatment were investigated. As a result, hydrargillite began to lose the structural water at about 200°C, and changed to mixture, of boehmite and intermediate alumina (amorphous) at 241°C. During the change of structure, surface hydroxyl groups of these powders were esterified at the same time, and the surface were modified to, organophilic or hydrophobic. Hydrargillite changed to boehmite or intermediate alumina in case of reflux treatment with solvent (alkane) only without alcohol, and a few organic material was introduced onto the surfaces. Its was presumed that a part of alkane was oxidized to carboxylic acid by reflux treatment and aluminum salt was formed. It was estimated that intermediate alumina produced by these treatments was ρ-alumina. In case of treatment of boehmite, the surface became organophilic properties, but the change of structure did not occured at all. Through these treatments, the shell of the particles kept the original form.
The effect of a low molecular weight additive in acrylic-melamine resin on its curing behaviour was studied by Dynamic Spring Analysis. Dioctyl Phthalate (DOP) was selected as an additive and its content in acrylic-melamine resin was varied. The following results were obtained. 1) The curing behaviour of resin varied as a function of DOP content. The maximum curing velocity was obtained at most suitable DOP content. 2) DOP was considered not to effect the curing mechanism but to decrease the viscosity of resin. This indicates that the probability of collision of functional-groups increased and the curing velocity was promoted by the addition of DOP.