Upcycling Pineapple Stem Waste into PLA-Based Bioplastics: The Role of Maleinized Linseed Oil in Film Performance and Biodegradability

Abstract

This study reports the development of sustainable packaging films based on polylactic acid (PLA) and thermoplastic starch (TPS), utilizing starch extracted from pineapple stem waste, an abundant and underutilized agricultural by-product in Thailand. Maleinized linseed oil (MLO), a fully bio-based compatibilizer, was incorporated to improve interfacial adhesion and enhance mechanical performance. PLA/TPS blends with varying MLO content were processed via twin-screw extrusion and film blowing. Mechanical testing showed that MLO significantly increased elongation at break to 43.21%, and thermal analysis indicated a reduction in T<inf>g</inf>, confirming the plasticizing effect of MLO and consistent with an increased interaction index of PLA/15TPS/MLO (5.28) compared to PLA/20TPS (5.03). SEM showed improved phase dispersion. The PLA/10TPS/10MLO blend demonstrates the most balanced properties. Biodegradation tests in soil and simulated marine conditions showed enhanced degradation in TPS-containing blends, although MLO slightly reduced the degradation rate by limiting water diffusion. The integration of agricultural waste valorization and green additives offers a promising route to fabricate biodegradable films suitable for single-use packaging applications, thereby contributing to circular economic efforts.