Iron as an alternative drier for curing of high-solid alkyd coatings

Alkyds are widely used polymers in the coating industry for decorative and industrial applications due to their low price, performance, diversity, and containment of renewable constituents. They have been of particular interest in research over the past decade owing to new legislative requirements focused on the reduction of volatile organic coatings (VOC) and the replacement of Cobalt (Co) driers. In the present work, the commercially accessible Fe (bispidon) drier and the Co (bis (2-ethylhexanoate)) drier were studied in high-solid (HS) alkyd coatings that are consistent with allowed VOC values as stipulated by actual EU legislation. Curing kinetic properties of the alkyd oxidation process were analyzed using FTIR spectroscopy. The influence of Fe and Co driers on crosslinking was further evaluated in terms of viscoelastic properties and surface hardness measurements. Finally, cured coating films were compared with the EIS method in order to determine the influence of driers on crosslinked polymer structures and pore resistance of HS alkyd coatings. We compared Fe and Co driers in HS long-oil alkyd coatings. Coatings with Fe drier showed comparable Final Drying Times but dissimilar crosslinking kinetic activity compared with the Co drier. Fe drier enable more uniformity through the entire thickness of the HS alkyd coating and consequently has lower diffusion of ions through the film.