Influence of UV Irradiation on the Degradation of Poly(butylene adipate‐co‐terephthalate) and Thermoplastic Starch‐Blended CuO Nanocomposite Films

ABSTRACT Blends of poly(butylene adipate‐co‐terephthalate) (PBAT) and thermoplastic starch (TPS) have garnered significant attention in food packaging due to their biodegradability and economic viability. To further enhance their properties and functionality, metal oxide nanoparticles, such as copper oxide nanoparticles (CuONPs), have been incorporated into these blends. However, the biodegradable nature of these blends renders them susceptible to various degradation factors, particularly photodegradation. This study investigated the photodegradation behaviour of PBAT/TPS blends, both pristine (PT) and with the addition of CuONPs (PTCu), under varying UV intensities and exposure durations. The results indicated that UV exposure induced significant changes in the surface morphology and thermal stability of both PT and PTCu films. The extent of degradation increased with increasing UV intensity and exposure time. Interestingly, the incorporation of CuONPs mitigated the photodegradation of the films. This was attributed to strong interactions between the CuONPs and the polymer matrix, as evidenced by 1 H NMR. FTIR spectroscopy and gel fraction analysis suggested that crosslinking occurs during photo‐oxidation under optimal UV conditions, leading to an increase in Young's modulus. However, prolonged UV exposure beyond the optimal levels results in material degradation. Additionally, extended UV exposure diminishes the antimicrobial activity of PTCu films against E. coli .