New developments in perfluoropolyether resins technology: high solid and durable polyurethanes for heavy duty and clear OEM coatings

摘要

Recent advances in perfluopolyether (PFPE) resin tdcnology for high solis, weather resitant polyurethanes for automotive (OEM) and heavy duty coatings are presented. In the former case, polyfunctional OH-terminated PFPE resins can be successfully blended with commercially available blocked isocyanates leading to high solids (70-80 wt.%) monocomponent polyurethanes with high density of cross-linking. Foirmulations containing PFPE resins and mixed hexamethylene diisocyanate/isophorone diisocyanate (HI/IPDI) blocked isocyanates were prepared and characterized according to OEM specifications; the perfomances of fluorinated coatings were compared with those of reference acrylic solvent-borne coatings. Clearcoats were appleid over conventional OEM basecoats (car body painting) the polyester powder coatings (wheels painting). The remarkable improvement of anticorrosion perofmances, acid and mair resistance and durability of painting system was reached maintaining its good aesthetic aspect. Fluorinated films showed excellent stain release properties conferring to final painting system, the self-cleaning behaviour typical for PFPE coatings. In the latter case, the use of dihydoxy terminated PFPE oligomers having properly selected moleuclar weights and bimodal molecular weight distribution allowed the preparation of really high solid (80-90 wt.% dry) low viscosity formualtions with aliphatic and cycloaliphatic hydorgenated polyisocyanates. The compositions were able to cross-link rapidly event at temperatures below 20deg C giving fully transparent, chemically resistant and easy-cleanable coatings. The coating phycial properties like hardness, glass transition temperature (T_g) and elongation can be optimized by tuning the hardener composition (HDI/IPDI ratio) as well as the moleular weight of the PFPE. White pigmented, high gloss finishes were also prepared and evaluated as protective barrier coating for heavy duty paints working in highly corrosive environments.