Rapid Composting Behavior and Properties of Sustainable PLA /Thermoplastic Corn Starch Compounds

Plastic food packaging extends shelf life but causes environmental pollution. Biopolymers such as poly(lactic acid) (PLA) are gaining interest as sustainable alternatives. However, PLA has limitations including slow biodegradation rate, brittleness, and high production cost. This study aims to address these issues by incorporating thermoplastic starch (TPS), a low‐cost, biodegradable biomass based on corn starch, into PLA to develop fast‐compostable biocomposites. Two commercially available PLA grades, a semicrystalline and a nearly amorphous grade, were employed to assess the impact of matrix crystallization on the performance and composting rate of the biocomposites. PLA/TPS blends containing 0–70 wt% TPS were prepared via twin‐screw extrusion and cast into 400 μm thick films. Thermoformed disposable food bowl containers were fabricated. Morphology, mechanical properties, thermal behavior, and biodegradability were investigated. The addition of TPS significantly accelerated the compostability of PLA by eliminating the lag phase and enhancing microbial activity. Tensile strength, along both machine direction and transverse direction, decreased up to 87% for biocomposites containing 70 wt% TPS. Increasing TPS content resulted in elongation at break enhancement of up to 300% for both PLA grades. These findings demonstrate that TPS not only reduces cost but also improves compostability and flexibility of the blends.