Nacre-like structural carboxymethyl cellulose dual-layered film with a combination of high strength, elongation, and UV-blocking for food packaging

Carboxymethyl cellulose (CMC) holds great potential for food preservation applications, provided its mechanical properties and UV-blocking performance are significantly enhanced. Considering this, the study focuses on developing a novel dual-layered film using the layer-by-layer casting method. The resulting film exhibits a compact dual-layered structure, with a nacre-like upper layer (chitosan/montmorillonite/tea polyphenols) and a dense bottom layer (CMC/sodium alginate/nano-hydroxyapatite/tea polyphenols). This design enhances tensile strength through hydrogen bonding interactions among nanoparticles, active substances, and polymers, while the nacre-like and layered structures contribute to improve elongation. Furthermore, the incorporation of tea polyphenols significantly enhances the UV-blocking performance of the film. Compared to the single-layer film, the dual-layered film exhibits improved tensile strength (from 45.19 MPa to 63.58 MPa), elongation (from 52.56 % to 82.45 %), and UV-blocking capability (from 99 % to 100 %). Additionally, the dual-layered film presents excellent water resistance (moisture content: 13.64 %, water solubility: 6.26 %), oxygen permeability (1.841 × 10 −3  g/m 2  s) and antioxidant activity (scavenging capability for DPPH: 67.25 %). When employed as packaging film, the dual-layered film effectively reduces tomatoes weight loss from 9.04 % to 7.52 % and extends shelf life. This study offers an innovative approach to promote the development of CMC for food preservation applications.