Accelerated Degradation of PLA-Based Composites in Harsh Alkaline Environment

The performance of poly(lactic acid) (PLA) bioplastics under harsh service conditions must be understood to enable their use in multi-use products. This work aims to investigate the accelerated degradation of PLA-based composites designed for multi-use cutlery and rigid packaging when exposed to an alkaline environment (pH 12, 70°C) for 30 days. Two formulations were studied: PLA reinforced with glass fibers (C) and with calcium silicate (RP). Mechanical testing, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier Transform Infrared Spectroscopy in Attenuated Total Reflectance (FTIR-ATR), and X-ray diffraction were used to correlate changes in tensile properties, surface morphology, chemical structure, and crystallinity. After aging, both composites showed strong embrittlement, with ultimate tensile strength dropping from about 80 to 25 MPa for the cutlery grade and from about 54 to 24 MPa for the rigid packaging grade, and strain at break decreasing from around 2% to below 1%. Surface analysis revealed pronounced erosion, microcrack formation, and a significant increase in roughness, especially for the calcium-silicate-filled composite, while FTIR-ATR and XRD indicated ester bond hydrolysis and higher overall crystallinity. These results demonstrate that the type of reinforcement critically controls degradation mechanisms and residual properties, providing guidelines for the design of more durable PLA-based bioplastics for demanding dishwasher-like and other harsh alkaline applications.