Amorphous polyamide coating resins from sugar-derived monomers

Abstract

In this article, the synthesis of bio-based polyamides for powder coating applications and their evaluation in a solventborne coating system are reported. The M n values of the resins were between 3000 and 4000 g mol À1 and the resins displayed T g values from 60 to 80°C. Both amine and carboxylic acid functionalities (total $0.6 mmol g À1 ) were introduced for curing purposes. The resins were cured with triglycidyl isocyanurate (TGIC) or N,N,N¢,N¢-tetrakis(2-hydroxyethyl)adipamide (Primid XL-552). The curing reaction was followed using rheology which indicated that TGIC achieved higher reaction rates and higher gel contents. The DSC analysis of the cured disks showed that all cured samples were amorphous as is desired for the targeted coating application. The resins required a curing temperature higher than 150°C. Aluminum panels were coated using a solventborne approach and the coatings were cured at 180°C during 1 h. Dewetting was observed on all panels. Network formation was adequate for an amine-functional resin cured with TGIC as indicated by solvent resistance testing. In conclusion, the developed biobased polyamide resins are promising materials to be used as binder resins in powder coating applications.