Polymer dispersion preparation by flow induced phase inversion emulsification. Part 1 The effect of silica on emulsification and dispersion characteristics

Low density polyethylene (LDPE) melt was emulsified in the presence of a hydrophobically modified water soluble polymer (HMWSP) and colloidal hydrophilic silica using the Flow Induced Phase Inversion (FIPI) emulsification technique. HMWSP was used as the surface active material. After the emulsification, LDPE melt was solidified to obtain a polymeric dispersion. Silica was used to aid the emulsification and improve the emulsion/dispersion characteristics. It was shown that the presence of silica increases the amount of aqueous phase necessary for phase inversion from water-in-LDPE melt to LDPE melt-in-water emulsion. The mean particle size and particle size span increased in the presence of silica. However, due to broader particle size distribution, the viscosity was lowered. The dispersions with silica appeared to form a more uniform film compared with the dispersion without silica. When the silica concentration is less than 1% in aqueous phase, an emulsion is obtained. At 2% silica level, a wet powdery material is obtained. This material can be diluted to obtain a dispersion or it could be used in powder coating.