Environmentally benign bio-based waterborne polyesters: Synthesis, thermal- and bio-degradation studies

With the rising impulse of environmental friendliness and sustainability, the polymer industries are aiming at developing environmentally benign sustainable polymers with desired properties for various applications. In this milieu, the authors wish to synthesize bio-based waterborne polyester using different bio-based reactants such as citric acid, glycerol, tartaric acid, dimer acid and sorbitol via catalyst-free and solvent-free polycondensation reactions. Three different compositions of the polyesters were synthesized by varying the citric acid and tartaric acid contents and characterized by different spectroscopic methods. Thermosets of the synthesized polyesters were obtained by crosslinking them with glycerol-based epoxy and poly(amidoamine) as a hardener. The performances of the cured polyesters were evaluated by mechanical, thermal, biodegradation and hemocompatibility tests. They showed excellent elongation at break (433.5-602.5%), toughness (9.27-17.23 MJ m(-3) scratch hardness (7.5-10 kg), gloss value at 60 degrees (89-95), impact resistance (10.78-14.95 kJ/m), moderate tensile strength (2.86-3.77 MPa), good thermal stability (above 210-222 degrees C) and chemical resistance. Moreover, the thermosets were also found to be biodegradable and hemocompatible with the erythrocytes present in RBCs. Thus, bio-based waterborne polyesters were synthesized successfully with desired properties via environmentally benign route and the thermosets have the potential for various applications including surface coating and biomedical.