Non-isocyanate polyurethane from sweet potato residual and the application in food preservation

Because of the increasingly environmental and health concerns over conventional polyurethanes that manifested by toxic isocyanates and unsustainable fossil-based polyols, there is a great interest in non-isocyanate polyurethanes (NIPUs) production from renewable biomass resources. Herein, under the concept of biorefinery, the sweet potato residue (SPR) from starch industry, rich in non-biological toxicity starch, holocellulose and vegetable protein, was considered as the raw material for the NIPUs. During the process, the crude SPR was first liquified into chain-extending homogeneous molecules that were enriched in active hydroxyl-groups, followed by undergoing epoxidation and carbonation. Then, the obtained cyclic carbonate precursor was crosslinked with amines for the final NIPUs. The as-prepared SPR-derived NIPUs exhibited attractive mechanical and thermodynamic properties. To test the applicability, the food preservation performances of the SPR-derived NIPUs was further investigated. After spray coating the NIPUs on the banana peel, the dark brown spots in the testing group were significantly reduced after half-month storage. Therefore, the SPR-derived NIPUs provides a foundation for the futural food packaging alternatives.