Synthesis of bio-based waterborne polyesters as environmentally benign biodegradable material through regulation of unsaturated acid structure

Abstract

Waterborne unsaturated polyesters has the characteristics of no emission or low volatile organic compounds (VOC), which has been widely used in environmental protection materials such as coatings, food packaging and so on. However, due to the crosslinking network formed by the cured carbon–carbon double bonds (C = C), how to maintain its biodegradability is still a difficult problem. In this paper, three kinds of aliphatic waterborne unsaturated polyesters with different compositions were synthesized from corn, citric acid and apple juice by melt polycondensation. Then, the waterborne unsaturated polyesters were further cured into films by the thiol-ene click reaction. Finally, the results showed the polyesters containing different unsaturated segment showed obvious differences in cross-linked density, mechanical properties and biodegradation rate. It was observed the cross-linking density (18.816 × 10-4 mol/mL) and the degradation rate (25.59 wt%) of the polyesters were the highest when the unsaturated double bonds were in the side chain. And the high degradation rate was attributed to the selective degradation of C-S-C bonds by glutathione and the secondary degradation of ester bonds by lipase. Thus, the combined biodegradable water-based polyesters have a wide application prospect as an environmentally friendly low volatile organic compounds coatings.