Citric acid/glycerol ester, a backup of 2, 2-bis(hydroxymethyl)propionic acid and biobased synthesis of anionic polyurethane dispersion

Nowadays biobased anionic polyurethane dispersions (PUDs) have been widely used in automotive, paints, coatings etc., but the strategies for achieving optimum properties are still highly challenging. Contrary to current knowledge, here glycerol ester of citric acid (GECA) was used as an internal biobased emulsifier for preparing high performance anionic PUD. Density functional theory (DFT) calculations revealed that GECA has comparable reactivity to the conventional bis(hydroxymethyl)propionic acid. GECA was prepared by an esterification reaction between citric acid and glycerol. The PUD was obtained by reacting GECA with isophorone diisocyanate in the presence of poly(ε-caprolactone) diol and monoglyceride of castor oil using a prepolymerization process. Films obtained from this PUD exhibited outstanding elongation at break (1469–1833%), good tensile strength (6.39–10.58 MPa), high toughness (65.47–95.71 MJm−3), adhesive strength (W-W) (13.06–43.29 kPa), thermal stability (330–385 °C), transparency (59–83%) and chemical as well as UV-resistance. PUD films also showed biodegradation under the exposure of Pseudomonas aeruginosa and Bacillus subtilis bacterial strains. Thus, the synthesized PUD is not only an eco-friendly material, but it has also high potential for industrial applications.