Facile synthesis of chitosan/Ag-waterborne polyurethane composite films with a high stability and controllable water resistance for potential application in antibacterial materials

Waterborne polyurethane (WPU) and Ag NPs have been applied widely in packaging. However, WPU was susceptible to the contamination due to high moisture absorption, and the stability of Ag NPs in matrix polymers was still low. To resolve this problem, chitosan (CS) was used as the dispersant to synthesize CS/Ag NPs composites in this work, and then they were mixed with WPU to prepare CS/Ag-WPU films. CS macromolecules provided the carriers for Ag NPs with a diameter of about 2.5 nm, and Ag NPs were dispersed stably in WPU. Compared with pure WPU film, as-prepared CS/Ag-WPU films had a higher thermal stability at low temperature, and the crystal size for WPU increased after introducing CS/Ag NPs. Importantly, the water contact angle for CS/Ag-WPU-5 increased to 54.2° from 27.5° implying that the hydrophobicity was improved. In addition, CS/Ag-WPU composites exhibited an excellent inhibitory effect on Escherichia coli(E. coli) and Staphylococcus aureus(S. aureus). Antibacterial performances of most samples were improved with the crease of the concentration of CS, and the inhibitory effect on S. aureuswas preferred. Therefore, as-prepared CS/Ag-WPU films in this paper have a potential application in antibacterial packaging field.