Wall-slip velocity as a quantitative measure of powder-binder separation during powder injection moulding

Abstract

This paper tends to point out the specific features of PIM compounds which should be taken into account in their rheological characterization as a necessary approach to optimize moulding step of the process. A lot of effort has been paid to describe the powder-binder separation during the flow through the mould channels in the quantitative way. Flow curves of the materials undergoing the structural changes during shearing are not a monotonically decreasing, but instead they exhibit minima/maxima upon increasing shear rate. Therefore, the multi-parameter rheological model, describing the flow peculiarities of PIM compounds, must be firstly developed and approved on reliable experimental data. Further, it is supposed that wall slip can serve as a quantitative parameter directly connected to the powder-binder separation. As it depends not only on material and processing parameters, but also on the microscopic nature of a channel wall, rheometer with special roughened plates was designed to carry out wall slip measurement.