Effect of the simultaneous biaxial stretching on the structural and mechanical properties of PLA, PBAT and their blends at rubbery state

International audienceThis works deals with the study of the strain-induced structural changes of PLA, PBAT andtheir blends with/without multi-functional styrene-acrylic oligomers (Joncryl ADR-4368).The films were prepared through a single-screw extrusion. Uni and bi-axially simultaneousstretching, at a temperature above the glass transition temperature, were performed. Theexperimental conditions were chosen so as not to generate significant thermal crystallizationduring tests duration. Stretching induced semi-crystalline films with a supposedin-plane mechanical isotropy. Their structural, morphological and thermo-mechanicalproperties were characterized using dynamic mechanical and thermal analysis (DMTA),differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), andtransmission electron microscopy (TEM). The strain-induced crystals of PLA combinedmesophase and alpha'-form crystals. Besides, the stretched PBAT was found to be composedof mixed-crystal structure of BT and BA units in a PBT-like crystal form. The Joncryl additionpromoted significant changes on the crystallization kinetics of PLA without affectingthe crystallization kinetic of PBAT. In fact, Joncryl acted as a nucleating agent making thusfaster the thermal crystallisation of PLA. In parallel, the strain induced crystallisation in PLAwas accelerated and stresses increased. The same effect was still observed in the PLA_PBAT blends