Constant Viscosity – Optimum End Product QualityOn a MRS extrusion line, the melt viscosity can be measured in real time with the Online Viscometer, VIS. Using a precision spinning pump, a small polymer flow is pumped in bypass through a precision capillary. Both the melt temperature and the melt pressure are measured (at two points) and using internal calculation software, the system works out the representative shear rate and viscosity.
When processing recycled PET with a varying residual moisture level and input quality, based on this melt viscosity measurement, it is possible to maintain the melt viscosity within a narrow tolerance band by changing the vacuum at the devolatilising section of the MRS extruder. With a control loop from the online viscometer VIS to the vacuum pump(s), the melt viscosity and therefore the IV of the end product can be maintained at the required level. While other manufacturers also offer online viscosity measurements Gneuss' MRS extrusion technology is the only technology to measure and actively control the end product IV.