Drying of porous coating: influence of coating composition

The influence of the coating composition of a porous paper coating on the evaporation rate of water contained in the sample has been studied experimentally. For low-content latex samples, drying was found to be mainly controlled by capillarity, perhaps also in the form of thin film pore surface feature/wall wetting, which drew water from the connected pores to the drying surface or near the surface. This led to a lengthy constant drying rate period (CDRP) where nearly 70% of the saturated water was evaporated. High-content latex samples, characterized by low porosity and permeability showed shorter CDRP and lengthy falling drying rate period. The drying rate curve varied linearly with time in the CDRP and with the square root of time in the falling rate period, indicating a diffusive controlled mechanism. Low latex content samples took less time to dry, which can be inferred to mean they require less drying energy.