Abstract. Films of EVOH copolymers, processed three times by twin-screw extrusion were prepared using a cast-film line. The variation on the melt flow rate (MFR) and rheological behaviour of the films were determined, as well as the thermal properties assessed by differential scanning calorimetry (DSC) and dynamic-mechanical thermal analysis (DMTA). As the results showed that the reprocessing induced an increase in the viscosity and orientation of the films, it was suggested that structural modifications from chain-extension or cross-linking reactions promoted by hydroxyl and residual acetoxyl groups, could be occurring. The successive self-nucleation and annealing (SSA) technique was applied, evidencing the structural modifications on the EVOH copolymer.

Abstract. The ductile-brittle transition behaviour of organo modified montmorillonite-based Poly(lactic acid) films (PLA/o-MMT) was analysed using the Essential Work of Fracture (EWF) methodology, Small Punch Tests (SPT) and Enthalpy relaxation analysis. While the EWF methodology could only be applied successfully to de-aged samples, small punch test (SPT) was revealed as more effective for a mechanical characterization during the transient behaviour from ductile to brittle. According to differential scanning calorimetry (DSC) results, physical aging at 30°C of PLA/o-MMT samples exhibited slower enthalpy relaxation kinetics as compared to the pristine polymer. Although all samples exhibited an equivalent thermodynamic state after being stored one week at 30°C, significant differences were observed in the mechanical performances. These changes could be attributed to the toughening mechanisms promoted by o-MMT.