Chemical transformation of renewable algae oil to polyetheramide polyols for polyurethane coatings

Algae are a group of photosynthetic marine or freshwater plants that exhibit high CO2 capturing capacity. Algae have been among the most promising renewable resources for overcoming climate change issues. In this study, algae oil (AO) was chemically transformed to polyols through two-step reactions and incorporated into value-added and industrially important polyurethane (PU) coatings. First, AO was reacted with diethanolamine to afford fatty amide. Then, polyetheramide polyols (AEAs) were prepared by reacting the fatty amide with bisphenol-A, 1,4-butanediol, or isosorbide. PU coatings were prepared by reaction between the AEAs and diphenylmethane diisocyanate. The PUs exhibited typical semicrystalline and three-step degradation behaviors with enhanced gel content values, supporting the high reactivity of the AEAs as polyols. The hydrophobic characteristics of the fatty acid chains of the AEAs resulted in decreased water absorption of the PUs, which improved the antimicrobial characteristics of the PUs. In particular, the PU coatings exhibited excellent resistance against alkaline aqueous media and organic solvent (xylene) along with reasonable gloss, hardness, flexibility. In saline aqueous media, the PU coatings exhibited anticorrosion performance superior to that of typical poly(tetramethylene ether) glycol-based PU coating. This study demonstrates the high potential of the PUs as anticorrosion and antimicrobial materials from the environmentally friendly renewable resource.