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Infiltration tests to assess the permeability and hydraulic conductivity of 3D printed plaster parts under different conditions

Abstract:

In the postprocess of infiltration in the Binder Jetting technology, the permeability (k) and hydraulic conductivity (K) are essential factors in the penetration of the infiltrant within the three-dimensional printing (3DP) model and thus get to improve its mechanical strength. This study experimentally evaluated the influence of 3DP sample thickness, infiltrant type, build orientation, binder saturation and colour of model 3DP on its permeability and hydraulic conductivity. Permeability and hydraulic conductivity were determined based on Darcy’s law in a custom-made falling-head permeameter with low- and high-viscosity mineral oils that simulated the infiltrants. In addition, porosity and the pore-size distribution were estimated using the liquid saturation and mercury intrusion porosimetry methods. In decreasing order, the build orientation and binder saturation of the sample showed a statistical significance for k, whereas for K the infiltrant type and build orientation were significant. The cumulative volume curves of intruded/extruded mercury to the 3DP model showed liquid entrapment, and this seems to be related to kinetic effects over mercury extrusion, together with the tortuosity and surface chemistry of the pores in the porous system. More than 90% of the pores detected are macropores (> 0.05 µm); however, the predominance in the absorption of the intruded mercury occurred in pores between 10 and 30 µm.