Which adhesion promoters would you recommend for acrylic and polyester paints intended for household appliance ?
Here we would recommend the use of silanes, which distincly improve the adhesion of the paints you mention. Various functionalities can be introduced into these silanes, so that there is good compatibility with the paint resin.
The adhesionof acrylic resins with hydroxyl and/or carboxyl functionality can be improved by adding about 1 % of a diaminofuntional silane. This became apparent especially after several days immersion in water. Other organo fuunctional silanes could also be used for this purpose, e.g. those based on chloropropyl, vinyl, methacrylate and epoxy resins, the last namely in cycloaliphatic form.
Another factor which is important in choosing a suitable adhesion promoter is its reactivity, which should be slightly greter than that of the paint resin, so that there is good adhesion to the substrate and achance for the additive to take part in the film forming process. Adequate migration of the silane is an advantage since thia enables it to quickly reach the interface.