Evaporation of Liquid Droplets on a Glass Platet

Abstract

The evaporation of a liquid droplet on native or hydrophobic glass, teflon and poly(vinyl chloride) plate was investigated from measurment of the contact angle and the bottom length of the droplet against time. The evaporation of a liquid droplet was found to be classified into two types (1 ) the bottom length of liquid droplet is constant until the contact angle decreases to a certain angle where the former begins to decrease with a constant contact angle and ( 2 ) the bottom length is constant while the contact angle decreases with evaporation. The evaporation of water droplet on the surface-treated glass plate, teflon and poly(vinyl chloride) is classified as type ( 1 ) and that of a droplet of water, in which powde ry concrete had been suspended, on surface-treated glass plate belongs to type ( 2 ). The rate equations of two types of evaporation were derived. These equations explain well experimental results. The receeding contact angle is discussed for the evaporation of ( 1 ). t The Appearance Mechanism of Permanent Stains on the Glass Plate. I. the type