Asymmetric porous emulsion film

The formation mechanism of an “asymmetric” porous structure for the film cast from ethyl acrylate-methyl methacrylate copolymer emulsion prepared by emulsifire-free emulsion polymerization was investigated. The formation of this structure was affected by the emulsion stability which was varied by the postaddition of sodium sulfate or sodium dodecyl benzene sulfonate. It is concluded that it is derived from the production of porous skin film at the emulsion-air interface and the precipitation of flocculated particles at the bottom of emulsion during drying process.