Enhancing Compatibility and Properties of Polylactic Acid/Polystyrene (PLA/PS) Bioblend for Sustainable Food Packaging: Experimental and Quantum Computational Insights

This study investigated the impact of incorporating maleic anhydride grafted styrene-ethylene-butylene-styrene (SEBS-g-MAH) at varying concentrations (2.5, 5.0, 7.5, and 10.0 wt%) into binary blends of polylactic acid (PLA) and polystyrene (PS) with a weight ratio of 75/25. The blends were prepared using melt mixing in an internal Brabender mixer, followed by compression molding. Various characterization techniques, including Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyses (TGA), differential scanning calorimetry (DSC), tensile testing, surface hardness measurements, and scanning electron microscopy (SEM) were employed to evaluate the structural, thermo-mechanical, surface, and morphological properties of the blends. FTIR results indicated the presence of n-π interaction between PLA and PS polymers. However, the introduction of SEBS-g-MAH to the blends resulted in specific interactions. TGA investigations demonstrated that compatibilized blends exhibited more excellent stability at high temperatures than their non-compatible counterparts. The DSC data align with the mechanical tests, revealing that the addition of SEBS-g-MAH reduced the crystallinity of the blends. Tensile strength, Young's modulus, and surface hardness diminished with the addition of SEBS-g-MAH, although the elongation at break improved. SEM analysis of the PLA/PS blends illustrated that incorporating SEBS-g-MAH enhanced the PS phase's distribution throughout the PLA matrix. Furthermore, molecular dynamic simulations revealed a significant enhancement in binding interaction energies upon adding SEBS-g-MAH, increasing from 2037.972 kcal/mol to 2826.946 kcal/mol for the PLA-PS and PLA-PS (5) systems, respectively. Density of state (DOS) analysis indicated that SEBS-g-MAH played an intermediary role, promoting compatibility between PLA and PS. These findings suggest that SEBS-g-MAH can effectively be a compatibilizer for PLA-PS blends.