Fatty Acid Surfactant Structure-Feedstock Flow Properties: Correlation for High-Pressure Ceramic Injection Molding

Abstract

The effect of four different fatty acids on the rheological behavior of polyethylene-paraffin-zirconia feedstocks was investigated systematically. The substitution of a small portion of the low-viscous paraffin by the fatty acid does not alter the binder viscoelastic flow characteristics. At high solid loads (50 and 55 vol%), the addition of small amounts of fatty acid surfactants causes a significant influence on the feedstocks flow properties. An optimized surfactant concentration around 2.2 mg/m 2 fillers' specific surface area could be estimated. From melt rheology experiments, a clear correlation between the fatty acid molecular extension and resulting feedstock viscosity could be derived.

Development of a Polyethylene Glycol/Polymethyl Methacrylate-Based Binder System for a Borosilicate Glass Filler Suitable for Injection Molding

“…Another possibility of viscosity adjustment and improved feedstock homogeneity was to choose an appropriate surfactant SA concentration. Initially, a value of 4.4 mg/m 2 was selected, which had been found to be well-suited for ceramics [ 18 ]. It was increased up to 20 mg/m 2 , which corresponds to approximately 3 wt.% of the binder.…”

“…For ceramics and metals, several binder systems are described in the literature, e.g., the mixture of polyethylene and wax in combination with SA as a surfactant has been widely used in PIM [ 18 , 19 , 20 ]. In addition, various binders based on partially water-soluble polymers such as PEG have been applied for environmental reasons, avoiding the abovementioned problematic hexane removal issue.…”

“…The SSA is the interface between the inorganic solid and the organic polymer matrix [ 31 ]. In the case of micro-sized ceramic fillers, such as Al 2 O 3 or ZrO 2 with typical SSA values around 6–12 m 2 /g, a solid loading of around 45–55 Vol% ensures a good molding behavior [ 18 , 27 , 31 ]. Use of micro-sized metal fillers with SSA values significantly below 1 m 2 /g enables higher solid loads between 60 and 65 Vol% [ 28 ].…”

New Partially Water-Soluble Feedstocks for Additive Manufacturing of Ti6Al4V Parts by Material Extrusion

“…In general, the compounding curve can be split in three phases, namely the filling phase, the mixing phase and, finally, the equilibrium phase [45]. From the torque vs. time diagram the quality of the resulted feedstock can be evaluated, e.g., a constant final equilibrium torque value is a strong hint for a homogenous feedstock composition [45]. The observed compounding behaviour is slightly different from the previously investigated wax/PE mixtures [36].…”

“…Figure 2a shows the time-depending compounding torque of the PEG/PVB mixtures without and with the three different investigated surfactants applying a PEG M W of 8000 g/mol. In general, the compounding curve can be split in three phases, namely the filling phase, the mixing phase and, finally, the equilibrium phase [45]. From the torque vs. time diagram the quality of the resulted feedstock can be evaluated, e.g., a constant final equilibrium torque value is a strong hint for a homogenous feedstock composition [45].…”