Biodegradable UV-Blocking Films through Core–Shell Lignin–Melanin Nanoparticles in Poly(butylene adipate-co-terephthalate)

Biodegradable and renewable UV-shielding films are highly demanded to meet the increasing sustainable requirement for the environment. Lignin as a natural broad UV blocker has gained considerable attention; however, the poor dispersibility within synthetic polymers limited its applications. Thus, a bioinspired melanin-like polydopamine thin layer was incorporated for the first time with lignin nanoparticle (LNP) in this effort, forming a UV-blocking core–shell lignin–melanin nanoparticle (LMNP) with higher compatibility and durability. Subsequently, LNP, LMNP, melanin nanoparticles (MNP), and a mix of LNP and MNP (MixNP) were compounded with poly(butylene adipate-co-terephthalate) (PBAT), to enhance the UV-barrier capability and photostability of PBAT films. The incorporated LMNPs were well distributed into PBAT, leading to improved tensile properties and thermal stability of the resulting films. All these films possessed remarkable UV-blocking capacity at NP concentration ranging from 0.5 to 5 wt %, blocking almost all of UV-A and more than 80% of UV-B light, while an appreciable optical transmittance could also be achieved. The PBAT–LMNP films displayed a high UV-shielding stability and the best retention in mechanical properties after UV exposure for 40 h. This work provides a very promising approach for fabricating biodegradable PBAT-based UV-blocking films for potential applications in agricultural or food packaging materials where the UV resistance is highly required.