A low-environmental-impact approach for novel biocomposites based on PLLA/PCL blends and high surface area graphite

In this work, novel graphite-based composites consisting of poly(L-lactide) (PLLA) and poly(epsilon-caprolactone) (PCL) immiscible blends are developed by means of a simple and low-environmental-impact method, which does not require the use of either solvents or graphite oxide. Indeed, the proposed approach relies on the preliminary dispersion of a high surface area graphite (HSAG) in the molten PCL by applying a sonication treatment: as a consequent of this processing, the HSAG turns out to be dispersed in the polymer matrix at a sub-micrometer level and acts as a nucleating agent for the PCL crystallization. The PCL/HSAG system (whose filler content is adjusted so as to prepare blends with final HSAG concentrations ranging from 0.1 to 0.6 wt.%) is subsequently introduced in PLLA through melt blending. SEM characterization demonstrates that the presence of HSAG modifies the morphology of the blend. In particular, at a characteristic HSAG concentration, namely 0.1 wt.%, the filler is observed to ameliorate significantly the compatibility of PLLA/PCL blends by increasing the interface adhesion between the two polymer phases. The peculiar morphology, promoted by the presence of HSAG at the interface, is found to enhance the mechanical properties of the blend, improving the elongation at break simultaneously increasing the Young's modulus. (C) 2015 Elsevier Ltd. All rights reserved.