Dimer acid based waterborne hyperbranched poly(ester amide) thermoset as a sustainable coating material

A dimer acid based waterborne hyperbranched poly(ester amide) (WHPEA) was successfully synthesized via a self-catalyzed and solvent free polycondensation reaction by using a novel citric acid derived polyamide polyol as branching unit and phthalic anhydride as the dibasic moiety. Citric acid acted as a bio-based internal emulsifier which was neutralized by adding triethylamine to obtain the waterborne polymeric system. Four different polymers were obtained by varying the mole composition of phthalic anhydride and dimer acid in between 4:1 and 1:4. The synthesized WHPEA was characterized by FTIR and NMR analyses. The mechanical performance of epoxy cured WHPEA was studied and compared to the analogues thermoset prepared without using neutralizing agent (HPEA). The result showed better mechanical performance of the later than the former. However, WHPEA exhibited better chemical resistance (except in alkali) and more thermal stability compared to HPEA. Bacterial degradation study with strain of P. aeruginosa revealed better degradation of WHPEA in comparison to HPEA thermosets. Thus, waterborne system was developed as an environmentally benign and sustainable polymeric material, which can be utilized as low VOC containing coating material. The work demonstrated the use of citric acid and dimer acid as a combined bio-based component in the synthesis of WHPEA coating for the first time.