The effect of a quenching treatment applied on heated cast sheet extruded films of two poly(lactic acid) (PLA)\ud commercial grades, with different optical purities, was studied. The thermal and mechanical properties of the films, as well\ud as their fracture behavior, were assessed by differential scanning calorimetry (DSC), tensile tests, and the essential work of\ud fracture (EWF) approach. The heating-quenching treatment causes a de-aging effect with an increase in the free volume of\ud polymer chains evidenced by a decrease in the glass transition temperature (Tg) and a decrease in the tensile stiffness and\ud yield stress. As a result, there is an abrupt increase in ductility, finding a dramatic change in the fracture behavior, from brittle\ud to ductile. The use of digital image correlation (DIC) of the strain field analysis during fracture testing has allowed relating\ud the decrease on the yield stress promoted by quenching with the crack propagation kinetics. The use of the EWF method\ud to characterize the fracture toughness of PLA has allowed to measure this enhancement on toughness, finding that the specific\ud essential work of fracture (we) and the plastic term (!wp) parameters increased 120% and 1200%, respectively, after\ud the quenching process.Peer ReviewedPostprint (published version

In this study the influence of the morphology in the polylactic acid/Cloisite30B (PLA/C30B) composites on the mechanical and fracture behavior of calendered films was evaluated. An image analysis was performed using TEM micrographs in order to complete the morphological study. The micrographs were taken from ultramicrotomic samples corresponding to the melting flow (MD) and transverse direction (TD) of the films. The image analysis showed intercalated particles and tactoids, which was in accordance to the wide angle X-ray scattering (WAXS) patterns. TEM micrographs also revealed highly oriented particles. Uniaxial tensile tests were performed in the MD and TD directions finding a slight anisotropy of the films, which was associated to low level of chains orientation due to the calander processing. The fracture behavior was also evaluated in the MD and TD directions using deeply double-edge-notched (DDENT) specimens. The mechanical and fracture tests were evaluated on aging (brittle) and deaging (ductile) films. For ductile PLA/C30B composites, the reinforcement effect promoted by the clay particles was not evident.