ISO 11443:2021 outlines methods for assessing the fluidity of plastic melts subjected to shear stresses at rates and temperatures that approximate those encountered in plastic processing. The importance of testing plastic melts according to these methods is underscored, as the fluidity of plastic melts is not solely determined by temperature but also influenced by other factors, including shear rate and shear stress.
The techniques described in this document are designed to measure melt viscosities ranging from 10 Pa*s to 107 Pa’s, depending on the measurement range of the pressure and/or force transducer and the mechanical and physical properties of the rheometer. The shear rates experienced in extrusion rheometry range from 1 s-1 to 106 s-1.
The elongational effects at the die entrance can lead to extrudate swelling at the die exit. Methods for evaluating extrudate swelling have been included in this document.
While the rheological techniques described here are not limited to characterizing wall-adhering thermoplastic melts alone, they can be applied to materials exhibiting “slip” effects [1][2] and thermosetting plastics. However, the methods used to determine shear rate and shear viscosity are not applicable to materials that do not adhere to the walls. Nevertheless, this document can be used to characterize the rheological behavior of such fluids for a given geometry.
