Rheological Properties and Stability of Highly Concentrated Water-In-Oil Emulsions with Different Emulsifiers

An investigation was performed into the effect of emulsifiers on the rheological properties and stability of highly concentrated water-in-oil emulsions (HCEs). The emulsifiers were oligomers of the polyisobutylene succinic anhydride (PIBSA) based on different head-group and relatively low molecular weight sorbitan monooleate (SMO). The viscosity and storage modulus of HCE depend on the nature of head-groups of PIBSA-based emulsifiers and the ratio of SMO. It was shown that an increase in the SMO concentration results in the increase of viscosity and storage modulus. The stability of HCE with aging is also influenced by the nature of emulsifiers. The results of the precipitation of ammonium nitrate and the change of storage modulus with time show that the increase in the ratio of SMO decreases the stability of HCE. It was found that the phase transition of ammonium nitrate is important for the stability of HCE.