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THERMOPLASTIC COATINGS AND INFRA RED OVENS

Plascoat recommend the use of air-circulating ovens for the curing or post-heating of thermoplastic coatings. Thermoplastic coatings are designed to work purely by melting on heating and re-solidifying on cooling. No reaction takes place other than that required for adhesion to the substrate.

Plascoat would recommend that users should avoid using IR ovens for curing of thermoplastic powders wherever possible.

IR ovens work by exciting the chemical bonds of the thermoplastic to produce heat. They do not heat the thermoplastic up directly. The heat from the chemical groups is transferred indirectly to the base thermoplastic. The IR radiation will also tend to heat the surface in preference to the body of the coating.

If the chemical groups become too excited (locally 'too hot') cross-linking can occur and in some cases a mixture of cross-linking and polymer chain scission - resulting in a poor surface finish, mattiness and a waxy 'feel'.

If the use of infra-red ovens cannot be avoided, Plascoat recommend that every other IR panel is switched off and/or that the intensity be set to a maximum of 50% capacity. If this cannot  achieve a smooth finish, the use of an additional air circulating oven is suggested.

 WGOD/040308 (Mod 011209PB)