Improvement of microstructures and properties of biodegradable PLLA and PCL blends compatibilized with a triblock copolymer

Incompatibility and immiscible binary blends of poly(L-lactide) (PLLA) and poly(epsilon-caprolactone) (PCL) with 70/30 wt.% composition were modified and prepared by addition of 0.5, 1 and 2 phr of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblock copolymer. The effect of the copolymer ratio on the microstructures and properties of the blends was investigated using proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscope (FE-SEM), dynamic mechanical analysis, differential scanning calorimetry, thermo-gravimetric analysis, and Mode I fracture testing. The addition of the copolymer to PLLA/PCL improved its fracture toughness. A reduction in the amount of spherical of PCL upon the addition of copolymers was confirmed by FE-SEM. The glass transition temperature (T-g) and melting temperature (T-m) of PLLA and PCL shifted closer together, indicating that the blend compatibility increased. Thus, PEO-PPO-PEO can be employed as compatibilizer to improve the toughness and compatibility of PLLA/PCL blends. (C) 2010 Elsevier B.V. All rights reserved.