THE DRYING OF COATINGS ON THICK WEBS

Abstract

The spreadsheet DRYWEB to predict the drying of coated webs assumes that the temperature at any location is constant across the coating and the web. But in drying a coating on a thick web, such as on a foamed plastics, the temperature across the web varies even though it will be uniform across the thin coating itself. To model heat conduction in the web a finite difference formulation is now used. Otherwise the spreadsheet, called DRYWEBTW, is very similar to DRYWEB. Examples show that with a thick, insulating web very little heats flows into the web from the coating. At an intermediate thermal conductivity more heat flows into the web and the drying rate is reduced. With a higher conductivity and with two-sided heating, heat can move by conduction from the backside of the web into the coating and thus increase the drying rate.