Copolymerized and blended poly(L-lactic acid)-based films with potential for dairy packaging: Soil degradation behavior

Biodegradable PLLA-based cast films were prepared via melt blending poly(L-lactic acid) (PLLA) with poly(L-lactic acid-co-butylene itaconate) (PLBI), poly(L-lactic acid-co-glycolic acid) (PLGA), and poly(L-lactic acid-co-butylene itaconate-co-glycolic acid) (PLBIGA) copolymers to enhance mechanical, barrier, and degradation properties for dairy packaging applications. Copolymers were synthesized using a one-step melt polycondensation method, and the film properties were effectively controlled by adjusting the blending ratios. All blended films exhibited significantly improved toughness while maintaining high transparency. Specifically, PLLA/PLBIGA20 % film demonstrated a 90.1 % reduction in oxygen transmission rate (OTR) and a 54.3 % reduction in water vapor transmission rate (WVTR) compared to pure PLLA, and PLLA/PLBI20 % film reduced ultraviolet (UV) transmittance to 53 % in the 280–320 nm range. The soil degradation rates of blended films were notably higher than pure PLLA, with distinct degradation mechanisms observed for each copolymer; notably, PLLA/PLBIGA20 % film degraded simultaneously in both amorphous and crystalline regions. Blended films met food-contact safety standards and, when applied to commercial yogurt packaging, effectively preserved lactic acid bacteria viability, outperforming pure PLLA film. These findings demonstrate the strong potential of PLLA-based blended films as sustainable packaging solutions for dairy products.