Poly(lactic acid)/Poly(vinyl alcohol) Biodegradable Blends Using Monobutyl Maleate as a Plasticizer and Compatibilizer

The Covid-19 pandemic situation has contributed to sparking discussions about an increase in packaging combined with the nonrecommendation of reuse. For this reason, many countries have encouraged the use of biodegradable polymers. In this study, blends of poly(lactic acid) (PLA) and poly(vinyl alcohol) (PVAL) were prepared at 80/20 (w/w) in the presence of specific amounts of monobutyl maleate (MBM) as a compatibilizer. All of these components are proven biodegradable. PLA/PVAL/MBM blend films were obtained by thermopressing, and the thermal, mechanical, and morphological properties were evaluated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile tests, stress relaxation, and scanning electron microscopy (SEM). DSC results suggest that MBM can act as a plasticizer, at least for the PLA matrix, reducing the Tg from 60.2 °C (without MBM) to 23.5 °C in the case of the highest quantity of plasticizer (20%). Due to increase in macromolecular mobility, MBM also affects PLA crystallization. As a consequence of brittleness of the other samples, only those containing 15 and 20% of MBM (in PLA basis) did not fail the tensile and relaxation tests, showing more than 25% of elongation at break. Both the elastic and viscous parameters and the equilibrium modulus (Eeq) of the Maxwell–Wiechert mechanical system show lower values for the sample with higher MBM content. The SEM images show that the presence of the compatibilizer improves the adhesion between the PLA-rich phase and PVAL-rich phase.