Intrinsic viscosity emulsion droplets

Because the presence of an electrolyte increases the dimensions of micelles and microemulsion droplets [115], it may be expected that in presence of ions the size of microgels is also increased. This expectation could be confirmed external electrolyte increases Mw (Fig. 21) as well as dz and [r ] (Fig. 22) up to the limit of the emulsion stability. Therefore, the addition of an external electrolyte to the reaction mixture for the ECP of EUP and comonomers is a means to vary the molar mass, the diameter and the intrinsic viscosity of microgels from EUP and comonomers deliberately. 

Buzza et al. (105) have presented a qualitative discussion of the various dissipative mechanisms that may be involved in the small-strain linear response to oscillatory shear. These include viscous flow in the films. Plateau borders, and dispersed-phase droplets (in the case of emulsions) the intrinsic viscosity of the surfactant monolayers, and diffusion resistance. Marangoni-type and marginal regeneration mechanisms were considered for surfactant transport. They predict that the zero-shear viscosity is usually dominated by the intrinsic dilatational viscosity of the surfactant mono-layers. As in most other studies, the discussion is limited to small-strain oscillations, and the rapid events associated with T1 processes in steady shear are not considered, even though these may be extremely important. 

Emulsion and deformable droplet emulsion intrinsic viscosity, respectively... 

Some experimental results ate available on model emulsions to test the viscosity relation. Nawab and Mason (1958) prepared fairly monodisperse butyl benzoate oil droplets, a cr 3 (im, by electrical atomization. The droplets were suspended in various water solutions and stabilized with a nonionic surfactant. scosi-ties were measured in a capillary viscometer at shear rates of200to 900 s . Their results are plotted in Figure 10.2.6. TTie agreement between theory and experiment for intrinsic viscosity (0 = 0 limit) is excellent. 

At relatively low concentrations, gum arabic yields solutions that are essentially Newtonian in behavior and have very low viscosities compared to other polysaccharides of similar molecular mass. This behavior is similar to that of globular proteins. The intrinsic viscosities at pH 5.5 of gum arabic solutions are similar to those of P-lactoglobulin. Randall et al. [158] and Williams et al. [148] concluded that the AGP fraction is responsible for the gum s emulsifying ability. Consequently, relatively high concentrations of gum arabic are required to produce stable emulsions of relatively small droplet size. At a lower gum arabic concentration, there is insufficient surface-active material to fully coat all the droplets. Therefore, it has been concluded that although gum arabic is basically a polysaccharide, its interfacial and emulsifying properties are derived from its proteinaceous nature. 

---