Exploring g-C3N4 as a green additive for biodegradable poly(butylene adipate-co-terephthalate) film with enhanced UV shielding and mechanical properties

Abstract

Typical small organic dyes exhibit excellent UV absorption capabilities and are commonly used as additives to shield plastic films from photoaging. However, their tendency to decompose easily and migrate rapidly within a polymer matrix limits their service life. Herein we prepared g-C₃N₄ nanosheets and fabricated g-C₃N₄/PBAT films to investigate the effects of g-C₃N₄ on UV shielding and plasticizing of a biodegradable PBAT film. Photophysical characterizations revealed that an improved UV light barrier performance was achieved on g-C₃N₄/PBAT films compared to pure PBAT. Furthermore, the photoaging results show that g-C₃N₄ can stably exist in the PBAT matrix, enabling the aged g-C₃N₄/PBAT films to maintain their effective UV shielding ability, whereas the aged benzophenone (UV-0)/PBAT film shows a substantial decrease in UV light absorption due to the photodecomposition of UV-0. Additionally, g-C₃N₄ acted as a reinforcing material for PBAT, as evidenced by the approximately 1.5-fold increase in longitudinal tear strength and 1.6-fold increase in tensile strength of g-C₃N₄/PBAT films compared to pure PBAT. Remarkably, even after 100 hours of photoaging, the aged g-C₃N₄/PBAT films retained their favorable mechanical properties. This study highlights the potential of g-C₃N₄ as a new type of UV shield additive for future practical applications in protecting biodegradable plastic from photoaging.