Preparation and characterization of cardanol-based coatings through O2-drying/epoxy-anhydride dual-curing strategy

Abstract In this work, the synthesis of the multi-arm cardanol-based oligomer (HF) through the one-pot reaction of hydroxyethyl cardanol ether (HCE) and high methyl etherified melamine formaldehyde resin (HMMM) is carried out. The developed HF is cured under the oxygen (O2) atmosphere and monitored by differential scanning calorimetry and Fourier transform infrared spectroscopy. The speed of curing reaction between HF and O2 is significantly improved by adding cobalt naphthenate as a catalyst and raising the temperature. Then, a series of solvent-free coatings are prepared and characterized with different contents of HF along with commercial cardanol-based epoxy resin (PLR602A). The curing reaction of the coatings, namely PLR602A-anhydride and O2-HF, displayed that the glass transition temperature and heat-resistance of the cured film are improved with the increasing content of PLR602A. The mechanical properties of the solvent-free cardanol-based coatings revealed that the hardness of the coating is measured up to 3H. The introduction of 40 wt% of PLR602A improved the performance and showed the best combination of the hardness, adhesion, and gloss of the coatings.