Rheological, thermal and mechanical properties of biodegradable poly(lactic acid)/poly(butylene adipate-co-terephthalate)/poly(propylene carbonate) polyurethane trinary blown films

Poly(lactic acid) (PLA), poly(butylene adipate-co-terephthalate) (PBAT) and poly(propylene carbonate) polyurethane (PPCU) were blended by using a twin-screw extruder, and then, the PLA/PBAT/PPCU trinary blends were made into films via the blown film technique. The PLA/PBAT/PPCU blends were characterized by dynamic rheometer and differential scanning calorimetry (DSC). From the analysis of DSC, it indicated that the glass transition temperature (T-g) of PBAT and PPCU was increased and the glass transition temperature (T-g) of PLA was decreased with increasing PPCU content. PPCU could improve miscibility among PLA, PBAT and PPCU. The tests of mechanical showed that the elongation at break of PLA/PBAT/PPCU films decreased from 240 to 226% in the machine direction and from 413 to 353% in the transverse direction. The tensile strength was increased in the machine direction from 40.2 to 46.5 MPa in the machine direction and from 28.5 to 42.8 MPa in the transverse direction. The tear strength was from 1334.7 to 143.6 kN/m in the machine direction and from 137.3 to 147.8 kN/m in the transverse direction. PBAT was a good toughening agent for PLA, and PPCU was a compatibilizer for PBAT and PLA blends.