Coupling of poly(lactic acid) with a polyurethane elastomer by reactive processing

[Display omitted] •A segmented polyurethane elastomer was synthesized in poly(lactic acid) melt.•Reactive processing was compared with the conventional mixing of the components.•The successful synthesis of block copolymers was confirmed.•Isocyanate was found to react only with the hydroxyl end of poly(lactic acid).•Our results clearly show the benefits of reactive processing. A segmented polyurethane elastomer (PU) was synthesized in poly(lactic acid) (PLA) melt by reactive processing. The isocyanate component was anticipated to react with the end-groups of PLA resulting in the formation of block-copolymers. The stoichiometry of the functional groups was optimized in the preliminary experiments. Two different processing methods were compared in the further experiments: conventional mixing of PU with PLA (PLA/PU), and reactive blending (PLA-b-PU). The comparison of the structure and properties of compatibilized reactive blends and conventional physical blends clearly shows the benefits of reactive processing. Coupling resulted in a finer dispersion of the particles in the matrix leading to better mechanical properties in the reactive blend. The successful synthesis of PLA-b-PU block copolymers was confirmed by NMR spectroscopy. The isocyanate component was found to react only with the hydroxyl end-groups of PLA, while the formation of amide and acylurea groups was not detected on the carboxyl end.