Mechanical Performance and Compost‐Soil Degradation of Uncompatibilized PLA / PBAT / PCL Blends

The persistence and fragmentation of conventional petroleum‐based plastics used in agricultural and soil‐contact products have increased the need for biodegradable alternatives that can provide adequate mechanical performance during service while reducing long‐term persistence after disposal. This study investigated uncompatibilized poly(lactic acid) (PLA)/poly(butylene adipate‐co‐terephthalate) (PBAT)/poly(ε‐caprolactone) (PCL) binary and ternary blends to evaluate the balance between initial mechanical performance and subsequent degradation under compost‐soil conditions. The PLA content was fixed at 60 wt%, while the relative proportions of PBAT and PCL were varied to determine the influence of blend composition on mechanical, thermal, and degradation behavior. Among the investigated formulations, the ternary blend containing 60 wt% PLA, 20 wt% PBAT, and 20 wt% PCL (P6B2C2) exhibited the most balanced initial mechanical performance. P6B2C2 achieved approximately 73% of the tensile strength and 95% of the tensile modulus of neat PLA without the use of a compatibilizer. DSC analysis revealed distinct component‐specific thermal transitions, confirming the immiscible nature of the blends. The PLA melting temperature remained relatively stable at approximately 148°C–155°C, while PCL retained its characteristic melting peak near 56°C. During 60 days of compost‐soil burial, distinct composition‐dependent degradation responses were observed. The binary PLA/PCL blend (P6C4) exhibited approximately 46% weight loss, accompanied by extensive surface deterioration, cavity formation, and substantial loss of mechanical integrity. In comparison, P6B2C2 exhibited approximately 22% weight loss and retained greater structural integrity throughout the exposure period. SEM observations revealed progressive interfacial deterioration and matrix fragmentation, while FTIR spectra retained the characteristic ester bands without showing substantial formation of new functional groups. The combined weight‐loss, mechanical retention, and physicochemical analyses demonstrate that the degradation response of PLA‐based biodegradable blends can be tailored through blend composition. These findings highlight the potential of ternary PLA/PBAT/PCL blending to balance mechanical performance with soil degradation, providing a material level basis for developing biodegradable alternatives for short life agricultural and soil contact applications.