Process viscosity in a film coater

A mini film coater was built to investigate the rheological behavior of pap er coating colors and the film application on a paper web at commercial spe ed. As for the rheological characterization, the main idea is to use measur ements of metering nip pressure and torque on the metering rod to back calc ulate the viscosity (inverse problem). It was found that the values of proc ess viscosity are very different from those obtained in classical rheometry . This is explained by the rheological behavior of the suspension in the ni p, where it is subjected to a mix of high intensity extensional and shear d eformations for a very short period of time.