Optimization of the Rheological Properties of a PA66 – LCP Blend for Micro Injection Moulding

Injection moulded micro parts and microstructured surfaces require accurate replication of micro-scale features, which depends on polymer properties, features geometry and process parameters. This paper focuses on the effects of the rheological properties of a PA66, obtained by the addition of different content of LCP, and their effects on the replication capability. The addition of a Liquid-Crystal Polymer, in fact, strongly affects the rheology of the blend, lowering the shear viscosity and increasing the extensional viscosity. The decrease of shear viscosity can be exploit to enhance the replication of micro parts and microstructured surfaces by reducing pressure losses of the filling flow. On the other hand, an increase in the elongational viscosity yields higher entrance losses especially when the flow field is characterized by abrupt changes in cross section, as in the case of micro injection moulding. Several PA66-LCP blends were produced at different LCP content and then characterized by means of a capillary rheometer. An optimal value for the LCP content was determined by taking into account its effect on both shear and extensional viscosity.