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.
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