Effect of poly(ε-caprolactone-b-tetrahydrofuran) triblock copolymer concentration on morphological, thermal and mechanical properties of immiscible PLA/PCL blends

Abstract

In this study a low molecular weight triblock copolymer derived from ε-caprolactone and tetrahydrofuran was used as a non-reactive compatibilizer of immiscible PLA/PCL blends. Ternary blends with 0, 1.5 wt%, 3 wt% and 5 wt% copolymer and about 75 wt% PLA were prepared by single screw extrusion and characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile and Izod impact testing. SEM micrographs showed that the size of the dispersed PCL domains was practically constant regardless of copolymer concentration. This result can be explained by the low shear rate employed during processing step and a decrease of PCL viscosity by presence of the triblock copolymer. However, when the copolymer concentration increased, strain at break of PLA/PCL blends also increased. PLA/PCL blend with 0 wt% copolymer presented 2% strain at break, whereas PLA/PCL blend with 5 wt% copolymer exhibited 90%.