Details:
Summary:
The force required to separate a web stuck to a roll is generated by the negative pressure the adherent fluid applies to the web. � The maximum negative pressure, called tack pressure, is an important indicator of maximum stress applied to the web surface during converting operations such as printing, coating, and adhesive processes. � Tack pressure is measured with flush mounted pressure transducers when a web is present in the nip. � It is influenced by a number of process parameters including viscosity, velocity, web tension, takeoff angle of the web, and roll cover compliance. � The shape of the pressure distribution through the nip changes when a web is present. � A simple expression was found to correlate the tack pressure with other parameters for both Newtonian and shear thinning fluids without a web (Gates and Bousfield, 2015). � In this paper, this expression was extended to account for studies where a web influences tack pressure through web material properties and takeoff angle of the web take-up roller relative to the nip. � Takeoff angle can affect shear forces applied to the fluid by the web, which in turn can influence tack development and actual web release angle from the inked roll surface.