PLA maleation: an easy and effective method to modify the properties of PLA/PCL immiscible blends

In this study, maleic-anhydride-grafted polylactide (PLA-g-MA) was investigated as a potential compatibilizing agent for the polylactide (PLA)/poly(ε-caprolactone) (PCL) system, with the aim of enhancing the final properties of the two polymer blends. Indeed, PLA-g-MA was prepared via reactive blending through a free radical process and characterized by means of ¹H-NMR and titration measurements, which demonstrated that the employed procedure allows grafting 0.7 wt% of MA onto the polymer backbone, while avoiding a dramatic reduction of PLA molecular mass. The specific effect of the MA-grafted PLA on the features of the PLA/PCL system was highlighted by adding different amounts of PLA-g-MA to 70:30 (w/w) PLA/PCL blends, where the 70 % PLA component was progressively substituted by its maleated modification. The efficiency of PLA-g-MA as a compatibilizer for the PLA/PCL blends was assessed through SEM analysis, which showed that the dimensions of PCL domains decrease and their adhesion to PLA improves by increasing the amount of PLA-g-MA in the blends. The peculiar microstructure promoted by the presence of PLA-g-MA was found to enhance the mechanical properties of the blend, improving the elongation at break without decreasing its Young’s modulus. Our study demonstrated that not only the microstructure but also the thermal properties of the blends were significantly affected by the replacement of PLA with PLA-g-MA.