Speaker
Description
The additive manufacturing by molten material extrusion of edible and (bio-)resorbable parts based on zein, a protein by-product of corn starch production, opens up perspectives for application in food processing, biomedical or pharmaceutical fields.
Adhesion between deposited layers requires filaments spreading and diffusion of polymer molecules at their interface. Then, fusion-bonding has to be monitored and modelled in the case of the plasticized zein, to control its 3D printing. Such phenomenon is linked to melts surface tension (Γ), being the driving force of filaments sintering, and viscosity (η).
Melts fusion-bonding ability is generally assessed in an instrumented furnace and modelled using Frenkel-Eshelby’s approach, based on the measurement of bonding neck’s growth rate between two circular parts (i.e., powder particles, or filaments sections). This approach was recently enhanced by the acquisition in 3D of zein-based extruded filaments hot melt sintering by dynamic X-ray tomography (5.2 μm pixel size, 1 scan/s) on the ANATOMIX beamline of Synchrotron SOLEIL (4 filaments disposed as 2 superimposed layers; L_Filament=5 mm, ∅_Filament=2 mm).
The rate of central pore collapse is assessed from the reconstructed volumes and leads to the evaluation of zein-based filaments viscous sintering kinetics. 2D and 3D multiplysics modelling, including multiphase flow, heat transfer and surface tension, are carried out by FEM combined to Level Set with COMSOL Multiphysics®. Such approach requires a simplification of the geometry, thanks to symmetry of the considered volume and an adaptive time-stepping.
At 120 °C, a typical temperature to process zein, 2D and 3D simulated, as well as experimental sintering kinetics are similar, with a decrease rate of the central pore at about 1%/s. Increasing bonding rates are obtained as surface tension and temperature increase, especially through the impact of the latter as reducing melts viscosity.
| Country | France |
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