Optimization of Near Infrared Cured Polyester/Melamine Coil Coatings by the Use of Near Infrared Absorbing Primers

Abstract

Near Infrared (NIR) radiative curing is a fast
thermal curing technology used to cure 25 micron polyester
melamine industrial coil coatings on galvanized steel substrate.
The cure is optimized when the top coat is relatively transparent
to NIR and with most NIR absorption taking place at the
substrate surface. In this study UV/Vis/NIR spectroscopy and
lab scale curing trials with a white top coat were used to show
that absorption in the bottom most layers of the coating system
can be taken a stage further by the addition of NIR absorbing
pigment to the primer layer. The results show energy efficiency
benefits for NIR cure by increasing the amount of incident
radiation absorbed without altering the colour properties of the
coating. A similar smaller benefit is also evident with a
conventional convection cure.