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

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 (O-2) atmosphere and monitored by differential scanning calorimetry and Fourier transform infrared spectroscopy. The speed of curing reaction between HF and O-2 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 O-2(-) 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.