Processing‐Controlled Impact Toughening and Degradation Response of PLA ‐ PU ‐ DMA Blends: Morphology–Property Relationships Under Kinetic Mixing and Extrusion

Polylactic acid (PLA) is an attractive bio‐based polymer, but its low impact resistance limits its use in demanding applications. This study investigates how processing route controls phase morphology, impact dissipation, and early‐stage degradation behavior in ternary PLA‐polyurethane‐poly(dimethyl acrylate) (PLA‐PU‐DMA, 60‐30‐10 wt%) blends. The blends were prepared by twin‐screw extrusion and kinetic mixing to compare shear‐driven and friction‐driven compounding. Kinetic mixing produced finer and more homogeneous dispersion of the elastomeric and acrylate phases, increasing notched Izod impact strength to 27.6 kJ m −2 , more than twice that of the extruded counterpart. Morphological and mechanical analyses indicate that this improvement arises from enhanced interfacial continuity and activation of cavitation–shear yielding mechanisms. Thermal and rheological characterization confirmed the dependence of crystallization behavior, melt response, and processability on processing‐induced microstructure. Soil‐burial experiments over 3 months showed no significant mass loss, although thermal and mechanical changes indicated early‐stage degradation sensitivity. Overall, the results demonstrate that processing‐controlled morphology, rather than composition alone, is decisive for achieving impact toughening while maintaining early‐stage degradation sensitivity in PLA‐based ternary blends.