Abstract
To elucidate the stain mechanism for precoated metal (PCM), the effects of surface melamine concentration and stain temperature on the stain resistance of polyester-melamine films were investigated by characterizing the surface structure using the FTIR-ATR method and by measuring the crosslinking density of the bulk of the film.
The following results were obtained
(1) Melamine resin was concentrated in the surface layer of the film when an acid catalyst was used.
The surface melamine concentration and the hardness value of the surface (0.2μm in depth) increased with increasing acid catalyst content. On the other hand, these films had a layer that showed a lower hardness value at depths of more than 3μm.
(2) Stain resistance at room temperature was improved by increasing the surface melamine concentration.
(3) The effect of surface melamine concentration on stain resistance decreased with increasing stain temperature, consequently stain materials permeated deeply into the film as stain temperature increased. The stain temperature at which the effect of surface melamine concentration on stain resistance disappeared increased with increasing film glass transition temperature Tg.
(4) The stain resistance at temperatures of 140°C and above was controlled by the crosslinking density of the bulk of the film.
