Film formation from concentrated reactive silicone emulsions. 1. Drying mechanism

Drying mechanisms of concentrated, reactive poly(dimethylsiloxane) in water emulsions, stabilized by a polyethoxylated fatty alcohol, were studied by visual observation, gravimetry, attenuated total reflectance, and infrared microscopy. The effects of some parameters were investigated, namely, thick ness of the cast layer, surfactant concentration, and presence of a CaCO3 f iller. The drying process can be described as three successive fronts, para llel to the surface, moving in a vertical direction, from tbp to bottom. Th e first front transforms the color of the emulsion from white to transparen t, the second is a coalescence front, and the third restores the initial wh ite:color. The main effect of all studied parameters is to alter the global drying rate and drying duration. The fate of the surfactant and the struct ure of the film after drying are examined in parts 2 and 3 of this series, respectively.