Toughening of poly(l-lactic acid) with Cu3BTC2 metal organic framework crystals

Poly(l-lactic acid) (PLLA) and metal organic framework (MOF) composites were prepared by melt extrusion of PLLA with 5, 10 and 20% w/w of activated Cu3(BTC)2 MOF. The morphology and stability of injection-molded samples were evaluated using thermogravimetric analysis, differential scanning calorimetry (DSC), gel permeation chromatography, X-ray diffraction, and scanning electron microscopy (SEM). The composites showed improved toughness during the tensile tests as compared to the neat PLLA matrix. Toughness mechanism of the composites was studied using SEM and rheological studies. SEM images indicated that cavitation induced by debonding at the interface of PLLA and MOF particles during the uniaxial stress was primarily responsible for the improved toughness of the composites. The SEM images of the composites, the solid like plateau observed in the PLLA composites during the parallel plate rheology at low frequency, and the decrease in the cold crystallization enthalpy during the developed composites indicate potential for various applications, which include gas separation, energy and active packaging.