Effect of miscibility on mechanical and thermal properties of poly(lactic acid)/polycaprolactone blends

Abstract

Binary blends based on poly(lactic acid) (PLA) and polycaprolactone (PCL) were prepared by melt mixing in a twin-screw co-rotating extruder in order to increase the low intrinsic elongation at break of PLA for packaging applications. Although PLA and PCL show low miscibility, the presence of PCL leads to a marked improvement in the ductile properties of PLA. Various mechanical properties were evaluated in terms of PCL content up to 30wt% PCL. In addition to tensile and flexural properties, Poisson s ratio was obtained using biaxial extensometry to evaluate transversal deformations when axial loads are applied. Very slight changes in the melt temperature and glass transition temperature of PLA are observed thus indicating the low miscibility of the PLA PCL system. Field emission scanning electron microscopy reveals some interactions between the two components of the blend since the morphology is characterized by non-spherical polycaprolactone drops dispersed into the PLA matrix. In addition to the improvement of mechanical ductile properties, PCL provides higher degradation rates of blends under conditions of composting for contents below 22.5% PCL.