The concentration and molecular weight of PVA, used as protective colloid, have a very significant influence in the production of small particles.
In a previous work, we studied the influence of different factors on MVPs synthesis, namely the time of dispersion of the organic phase in the aqueous medium, and the concentrations of amine, polyester, and protective colloids , The role of the type of the amine in the stabilization of the W/O emulsion system has also been studied , as well as the effect of curing conditions on the particles properties , All these works dealt with average diameters below 10 /an.
This water-in-oil emulsion is then dispersed in an aqueous phase containing protective colloids [poly (vinyl alcohol) (PVA) and hydroxyl ethyl cellulose (HEC)1, and a final water-in-oil-in-water double emulsion is obtained.
Another possible factor would be a modification in the thickness of the surface layer of adsorbed water-soluble polymers (protective colloids) with increasing temperature.
Despite the presence of the protective colloids at the surface, droplet collisions originate temporary agglomeration.
The organic phase is emulsified in an aqueous solution of poly (vinyl alcohol) (PVA) and hydroxyl ethyl cellulose (HEC), which act as protective colloids. In order to promote the diffusion of water into the oil phase, UP is previously neutralized with an amine.
These protective colloids were dissolved in water at 80[degrees]C, stirring for 1 h to achieve complete dissolution.