Improvement of mechanical and barrier properties of PLA films via coated antimicrobial polyurethane

High performance and environmentally friendly films for food packaging play an important role in improving food safety and protecting the environment after discarding. In this paper, bio-based polycarbonate diol (PCDL), isophorone diisocyanate (IPDI), isophorone diamine (IPDA), N -methyldiethanolamine (MDEA) and 1,6-dibromohexane were employed as main raw materials to prepare a series of polyurethanes with quaternary ammonium groups (QPUs). Subsequently, a bio-based coated film named as PLA-QPU was prepared by uniformly bar-coating the polyurethane slurry onto one surface of the PLA film. The mechanical testing results exhibit that PLA-QPU film has high tensile strength (63 MPa) and toughness (196 MJ/m 3 ), and the PLA-QPU film is more stretchable with elongation at break increasing from 7 % to 47 % in comparing with uncoated PLA film. The antimicrobial testing results show that the antimicrobial ratio of the QPU film against E. coli and S. aureus was 91 % and 88 %, respectively . The water vapor barrier properties testing results reveal that PLA-QPU coated film has a significant water vapor barrier property (57.8 g/m 2 ·day). The PLA-QPU coated film was evaluated for packaging cherry tomatoes and it maintained fruit freshness, texture, and visual quality effectively for up to 16 days. Therefore, the high-performance PLA-QPU coated film shows great promise as sustainable in food preservation.