Bio-blend for longue life applications: Preparation and characterization

The present project focuses on the preparation and characterization of modified poly (lactic acid) mixtures using a chain extender (REX-PLA) with a biopolyamide (PA 10.10) (85% and 15%, respectively) by a process of Reactive extrusion with a simultaneous calendering system in a pilot plant. The main objective of this work is to study the effect of the processing parameters (collecting speed and calender thickness) on the morphology and final properties of the films obtained by the one-step extrusion/calendering process. The production of the films was divided in two steps. Firstly, REX-PLA was obtained by reactive extrusion, by reacting a commercial grade of PLA (PLA Ingeo 4032D ®) with multifunctional epoxide agent (Joncryl ® ADR-4300-F) in a twin-screw extruder. Once the REX-PLA obtained, the REX-PLA/PA films were produced. In order to improve the homogeneity of the material, the intermediate extrusion of REX-PLA/ PA pellets was carried out the pellets were then reinjected into the twin-screw extruder to form the final products. Seven different conditions, fruits of different speeds (3.75, 14, 28 and 36rpm) and calender thicknesses (0.3 and 1mm) combinations were obtained. The rheological, morphological, thermal, mechanical and thermo-mechanical characterizations were carried out by RDA, SEM, DSC, traction and DMTA tests, respectively. The rheological analysis reveals an increase in zero shear viscosity and a shortening of the Newtonian range of PLA-REX compared to the PLA Ingeo 4032D used to obtain the blends. In the same sense, an increase of the storage modulus is observed in the area of low frequencies, which suggests an increase The present project focuses on the preparation and characterization of modified poly (lactic acid) mixtures using a chain extender (REX-PLA) with a biopolyamide (PA 10.10) (85% and 15%, respectively) by a process of Reactive extrusion with a simultaneous calendering system in a pilot plant. The main objective of this work is to study the effect of the processing parameters (collecting speed and calender thickness) on the morphology and final properties of the films obtained by the one-step extrusion/calendering process. The production of the films was divided in two steps. Firstly, REX-PLA was obtained by reactive extrusion, by reacting a commercial grade of PLA (PLA Ingeo 4032D ®) with multifunctional epoxide agent (Joncryl ® ADR-4300-F) in a twin-screw extruder. Once the REX-PLA obtained, the REX-PLA/PA films were produced. In order to improve the homogeneity of the material, the intermediate extrusion of REX-PLA/ PA pellets was carried out the pellets were then reinjected into the twin-screw extruder to form the final products. Seven different conditions, fruits of different speeds (3.75, 14, 28 and 36rpm) and calender thicknesses (0.3 and 1mm) combinations were obtained. The rheological, morphological, thermal, mechanical and thermo-mechanical characterizations were carried out by RDA, SEM, DSC, traction and DMTA tests, respectively. The rheological analysis reveals an increase in zero shear viscosity and a shortening of the Newtonian range of PLA-REX compared to the PLA Ingeo 4032D used to obtain the blends. In the same sense, an increase of the storage modulus is observed in the area of low frequencies, which suggests an increase in the melt elasticity.in the melt elasticity. The morphological inspection allows to demonstrate that the calendering speed induces a certain orientation in the MD direction and that the higher the speed is the greater the induced orientation. Likewise, observations of the fracture surfaces of the tensile films tend to suggest that the conditions of highest velocities (28 and 36 rpm) are too oriented, meaning that under these conditions the theoretical point of maximum orientation that the material can support before it starts losing property was exceeded. Thermal analysis leads to the conclusion that PA has a higher crystallization kinetic than REX-PLA and that it exerts a nucleating effect on the latter's cold crystallization. The recorded heat fluxes show that both the speed and the thickness calendering influence the enthalpic relaxation associated with the glass transition zone, the cold crystallization and the melt-recrystallization process of the blends, although the speed appears to have a more significant impact. Finally, the comparison of the two in the melt elasticity. The morphological inspection allows to demonstrate that the calendering speed induces a certain orientation in the MD direction and that the higher the speed is the greater the induced orientation. Likewise, observations of the fracture surfaces of the tensile films tend to suggest that the conditions of highest velocities (28 and 36 rpm) are too oriented, meaning that under these conditions the theoretical point of maximum orientation that the material can support before it starts losing property was exceeded. Thermal analysis leads to the conclusion that PA has a higher crystallization kinetic than REX-PLA and that it exerts a nucleating effect on the latter's cold crystallization. The recorded heat fluxes show that both the speed and the thickness calendering influence the enthalpic relaxation associated with the glass transition zone, the cold crystallization and the melt-recrystallization process of the blends, although the speed appears to have a more significant impact. Finally, the comparison of the two heating cycles of the lowest orientation condition (3.75rpm_1mm) tends to suggest that the blends undergo a phenomenon of physical aging. The mechanical analysis allows to affirm that the inclusion of the polyamide completely changes the uniaxial tensile behavior of the REX-PLA, going from a fragile to a ductile behavior, with a stable neck propagation, although the loss of this ductility is observed after a certain time, probably because of physical aging. On the other hand, due to a large dispersion of results, possibly related with a heterogeneity of the orientation induced by the extrusion/calendering process, no correlation was observed between the experimental parameters and the characteristic mechanical properties. The thermomechanical analysis, besides proving the presence of some orientation induced in the MD direction by the extrusion/calendering process, tends to validate the conclusion of the morphological analysis according to which the films at high calendaring speeds (28 and 36rpm) present too much orientation