Summary
On both ecological and economic grounds, powder coating is assuming a prominent role amongst available coating systems, as this method is completely solvent-free. Powder coatings are applied in solid form to the material to be coated, then melted onto this material at a high temperature.
This project involved the investigation of the role of the various powder coating components in the coating process. Key issues have been the wetting of the material to be coated, the surface quality obtained and emissions associated with the process.
Results:
- The use of catalysers produces a significant acceleration in the cross-linking and curing sub-processes. At the same time, a clear reduction in reaction peaks has been achieved. By this method, the two-stage process is retained.
- The use of uretdion group-based hardening systems (internally blocked isocyanate) produces a two-stage curing reaction, which generates no emissions and proceeds at temperatures below 150 C.
- Additives analysed from the polyacrylate and polysiloxane groups produce a substantial reduction in the surface tension of the melted coating, thereby improving the wetting of the material to be coated. Through accumulation on the surface of the melted coating, these additives lead to the formation of a more homogeneous coating film.
- Colouring pigments produce a slight increase in the fusion viscosity. No differences in wetting behaviour have been identified.
