Modelling the behaviour of Non-Newtonian materials for Capillary Drawing

ABSTRACT

In this work the original Fitt model is adapted to include Non-Newtonian materials to model the behaviour of polymer tubes during the stretching process in a fibre draw tower. An experimental comparison is then conducted for tubes made of Polycarbonate and Poly(methyl methacrylate), which are both shear thinning materials. Each material is drawn down to three different sizes and the final inner and outer diameter are compared with the calculated final dimensions. The experimental results show both good agreement with the model using Non-Newtonian materials and differences with Newtonian predictions. The model can thus be a helpful tool to aid polymer fibre fabrication for fibres with air gaps.