Enhanced toughness of PLLA/PCL blends using poly(d-lactide)-poly(ε-caprolactone)-poly(d-lactide) as compatibilizer

Poly(l-lactide) (PLLA)/poly(ε-caprolactone) (PCL) blends traditionally show low ductility because of the immiscibility between PLLA and PCL. In this study, this ductility challenge was addressed by modifying the compatibility between PLLA and PCL using poly(d-lactide)-poly(ε-caprolactone)-poly(d-lactide) (PDLA-PCL-PDLA or PCDL) tri-block copolymer. PLLA/PCL and PLLA/PCL blends with 0.7 phr and 3.5 phr PCDL were prepared by melt-compounding and extrusion and analyzed. The compatibilized PLLA/PCL blend with 3.5 phr of PCDL exhibited an elongation-at-break of 43%, compared to 18% in uncompatibilized PLLA/PCL, although PLLA/PCL/PCDL3.5 showed the higher crystallinity of 10.0% compared to 3.1% in PLLA baseline. The stereocomplexation effect between PLLA and PDLA was confirmed with a melting peak of a stereocomplex crystallite at 212 °C through differential scanning calorimetry. PCDL compatibilization improved miscibility between PLLA and PCL as evidenced through the interfacial morphology analysis, and supported by the rheological analysis, which elucidated the enhanced melting viscosity and interfacial adhesion of PLLA/PCL. Overall, the compatibilization of PLLA/PCL blends with PCDL was effective in achieving an enhanced interfacial morphology and adhesion, and improved elongation-at-break