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(ɛ-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 (Tg) and melting temperature (Tm) 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.

Research highlights▶ The AL specimen exhibits phase separation. ▶ PCL phase is in the form of spherical shapes dispersed in the continuous PLLA phase. ▶ Spherical shape of PCL phase disappear with addition of the copolymer.