High Shear Rheology Calibration Procedures for Aqueous Latex Anilox Evacuation
Calibrating capillary rheometers with Bagley and Mooney corrections ensures precise aqueous latex transfer from anilox cells, preventing spatters and excess coat weight.
Viscous Shear Heating
Thermal Generation
Internal friction within moving polymer melts generates thermal energy known as viscous shear heating during high speed extrusion coating operations. Polymer chains slide past each other under extreme mechanical stress, converting mechanical input directly into thermal output within the fluid boundary layer. Extruder screw speeds and die geometries dictate the magnitude of this temperature rise across the processing channel.
Elevated melt temperatures degrade polymer chains when thermal limits exceed material thresholds during heavy gauge substrate applications.
Rheological Control
Polymer degradation alters melt strength and coating uniformity across paperboard substrates. High molecular weight resins exhibit severe chain scission under high shear rates, dropping melt viscosity unexpectedly before the liquid contacts the moving web. Operators adjust barrel cooling zones and feed rates to compensate for internal temperature spikes generated during high output runs.
Temperature monitoring sensors mounted near the die exit capture these thermal fluctuations, preventing pinhole formation in thin barrier layers.
Thermal Equilibrium
Machine stability depends on balancing external barrel heating with internal thermal generation during continuous extrusion runs. Cooling systems remove excess energy produced by rapid mechanical deformation to maintain consistent web adhesion speeds. High speed coating lines require precise thermal management to prevent substrate scorching and coating weight variations along the running edge.