Thermoplastic polyester resin is known for the fact that the heating condition has an effect on the
degree of crystallinity. Therefore, it seems certain that the coating condition will also affect the degree
of crystallinity of a coating film. We focused on the relationship between the cooling time employed in
the film preparation process and the degree of crystallinity as regards thermoplastic polyester powder
we developed. The coating was formed by dipping the test pieces in a fluidized polyester powder vessel.
The test pieces were subsequently cooled in air to form the film, and finally immersed in a water bath.
We refer to this cooling time in air as the air-cooled time. We found that when the air-cooled time
increased, the degree of crystallinity increased. Moreover, as the degree of crystallinity increased, the
adhesive strength and the specular gloss decreased. We therefore found that the improvement in the
film performance is related to the reduction in the air-cooled time.
Key words: thermoplastic polyester powder, cooling time, crystallinity, coating film, adhesion force,
specular gloss