Alkaline Lignin-Functionalized Water-Resistant Waterborne Polyurethane Polymer for Constructing Ultraviolet-Shielding and Mechanically Robust Antibacterial Composites

Herein, highly transparent alkaline lignin (AL)-decorated, environmentally friendly, water-resistant waterborne polyurethane (WPU) antibacterial composite films (WPU/AL-MC) were constructed by incorporation of 1-chloro-2,2,5,5-tetramethyl-4-imidazolinone (MC) N-halamine biocide via a facile solution-casting technique. Interestingly, as-synthesized WPU/AL-MC films showed reinforced mechanical properties (20.80 MPa) and high-efficiency ultraviolet (UV)-shielding performance (over 85% of the UVA spectrum) compared to pristine WPU. The antibacterial rates of WPU/AL-MC films (0.8 wt % MC) against the inoculated model strains, Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), could reach 100% after 5 min of contact. Additionally, an obvious inhibition zone further potentially confirmed the release-killing mechanism of MC, which gave evidence that the WPU/AL-MC films illustrated rapid and persistent biocidal activity owing to the combination of contact-killing and release-killing processes. Meanwhile, the WPU/AL-MC films exhibited an adequate swelling ratio, well-maintained thermal stability, and prominent storage stability. At a very low filler loading of MC, the proposed antibacterial films also exhibited remarkable preservation capacity and could be used for fresh-keeping fields. Overall, this insight has a guiding function toward the simple approach for fabricating and structurally designing high-performance advanced WPU composite films in packaging utilization.