Mechanically Robust and Degradable Poly(urethane-urea) Plastics Derived from Tannic Acid and Castor Oil for Enhanced Fruit Preservation

Abstract

Traditional packaging plastics derived from fossil fuels for perishable foods have caused severe environmental pollution and resource depletion. To promote sustainable development and reduce wastage of perishable products, there is a significant challenge in developing bio-based packaging plastics that offer excellent preservation, satisfactory mechanical performance, and inherent degradability. In this study, poly(urethane-urea) (PUU) plastics are fabricated using a one-pot polyaddition reaction involving castor oil (CO), tannic acid (TA), lysine-derived ethyl 2,6-diisocyanatohexanoate (LDI), and H₂O. The resulting PUU plastics demonstrate a high breaking strength of about 32.7 MPa and a strain at break of ca. 102%. Due to the reversibility of hydrogen bonds, PUU plastics can be easily shaped into various forms. They are non-cytotoxic and suitable for food packaging. With a high TA content of ca. 38.2 wt%, PUU plastics exhibit excellent antioxidant capacity. Consequently, PUU plastics show outstanding freshness preservation performance, extending the shelf life of cherry tomatoes and winter jujubes for at least 8 days at room temperature. Importantly, PUU plastics can autonomously degrade into non-toxic substances within ca. 298 days when buried in soil.