Solid‐phase synthesis of grafted carbon black for superior aging resistance in biodegradable poly(butylene adipate‐co‐butylene terephthalate) composite films

Abstract Biodegradable films mitigate plastic pollution but often lack UV‐aging resistance, shortening their lifespan. While anti‐aging additives can boost the films' durability, small molecule migration constrains the extension of their service life. This study introduces a straightforward solid‐phase reaction for producing carbon black (CB) grafted with the UV absorber UV531, termed CB‐UV531. This material was then blended with the biodegradable polymer PBAT and transformed into a film via blow molding, yielding a durable UV‐resistant biodegradable film (PBAT/CB‐UV531). This solid‐phase grafting reaction does not require any solvents, thereby reducing solvent contamination and waste, and it is simple to operate, allowing for scalable production. Compared to the unmodified CB, the obtained CB‐UV531 exhibits significantly improved thermal stability, which can effectively reduce the loss of UV531 during the subsequent high‐temperature film‐blowing process. Furthermore, the chemically bonded UV absorber on the surface of CB‐UV531, coupled with its reduced particle size, promotes enhanced dispersibility and consistent stability within the PBAT/CB‐UV531 film, markedly improving its long‐term resistance to UV aging. This method is expected to enhance the anti‐aging effects of various commercial light stabilizer additives and can be used to extend the lifespan of different biodegradable materials. Highlights A simple solid‐phase reaction method was developed to prepare CB‐UV531. CB‐UV531 reveals smaller size and superior dispersibility. Biodegradable PBAT/CB‐UV531 film was prepared via a blowing process. UV531 migration loss in PBAT/CB‐UV531 film is significantly reduced. PBAT/CB‐UV531 film shows enhanced thermal stability and aging resistance.