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.
Dry film thickness on hull outside of two mammoth oil tankers which were built in two representative shipyards of Japan were measured in the numerous points. Intending to establish rational coating of hull outside which gives minimum variation of film thickness, these data were analyzed to make clear the relation of the dry film thickness and its variation with various factors in coating. The fifteen factors which influence upon film thickness were picked up, including “Ships”, “Shipyards”, “Painting schemes”, “Port and starboard”, “Blocks”, “Painting workers”, “Atmospheric temperature in coating” and “Checkers of dryfilm thickness”. Dry film thickness data of 13,000 were collected and an electronic computer was used to analyze them. Factors in coating and film thickness data were coded. The analysis programs were punched to paper cards and HITAC 8,400 was used for the analysis. The results were as follows; (1) Average paint film thickness x which was controlled by the minimum for B ship in its contract was greater than that for A ship which was controlled by the mean in its contract. (2) Variation of film thickness data from small blocks was larger than that from big blocks. (3) With regard to chlorinated rubber paint film, the high temperature in coating make both x and σ bigger than the low temperature in coating. While as to tar-epoxy paint, no tendency was observed. (4) The x value from two paint sprayers were nearly equal to contract film thickness and the σ value from these workers were not so large. Where as x from another paint sprayer was much higher than the contract film thickness, and σ was also large. (5) As to the bottom and the topside part, both x and σ from parallel body were smaller than those from the bow part and the stern part composed of many curved surfaces. As to the boot top part, there was no tendency of this kind.
It was tried to crosslink poly (tetra-hydrofurfuryl acrylate) by ultraviolet irradiation, adding cobalt naphthenate, calcium naphthenate or Michler's ketone as catalysts. High-pressure mercury lamp, UV carbon arc and chemical lamp were used for light sources and irradiation of the samples was carried out in the air in vacuo. Weight losses of the irradiated samples immersed in acetone for 8 hr at room temperature were measured. Degrees of crosslinking of the samples were estimated from the weight losses and infra-red absorbtion spectra. Characteristic UV absorbtion wave length of the polymer was measured by spectrophotometer. (1) High-pressure mercury lamp was most suitable to crosslink the polymer. (2) Weight losses of the samples containing 1 % of cobalt naphthenate was considerably small. (3) When the samples were irradiated in the air, degree of crosslinking was increased, because of opening the THE-ring as well as auto-oxidation. (4) Characteristic UV absorbtion wave length of the polymer was among 240~270mμ.