Effect of TPU hard segment content on the rheological and mechanical properties of PLA/TPU blends

Blends of an amorphous polylactide (PLA) with three different thermoplastic polyurethane (TPU) grades having various hard segment (HS) contents are prepared at the blending ratio of 85/15 wt% through a twin-screw extruder (TSE) at processing temperatures of 150 and 190°C. Blends of a semicrystalline PLA with 15 wt% of the noted TPU grades are also processed in the TSE at 190°C to investigate the matrix crystallization effect on the morphology and property enhancements. The rheological experiments reveal that the increase in TPU HS content significantly increases the phase compatibility between PLA and TPU as also suggested by the finer morphology of the TPU phase, although the use of lower HS TPUs is more favorable to enhance the ductility and impact properties of the blends.