Film formation from concentrated reactive silicone emulsion: 3. film structuring

摘要

Film formation mechanisms from concentrated emulsions of reactive polydimethylsiloxane in water, stabilized by a polyethoxylated fatty alcohol, were studied. Following Part 1 in this series, devoted to drying mechanisms, and Part 2, to surfactant distribution, this part deals with film structuring. Three layers were observed in the thickness: a top transparent, elastic skin, made of coalesced drops; in intermediate white, non cohesive layer; and a white, cohesive layer in contact with the substrate, containing separate surfactant domains as a dispersed phase. Structuring essentially depends on the local rate of water elimination, which is itself directly connected to the global drying rate. The total amount of surfactant in the emulsion seems also to play a specific role.