Challenges for industrialization of miniemulsion polymerization

This paper encompasses classic trends as well as recent advances in the understanding of emulsion inversion phenomena. The generalized formulation issue is first discussed from hydrophilic−lipophilic balance to the most recent concepts. The so-called standard inversion line on the formulation−composition map exhibits several branches, referred to as transitional and catastrophic inversions, that bound normal and abnormal emulsion regions. Dynamic inversion is also discussed with its hysteresis zones, where both types of emulsions may be attained, depending upon the system's previous history of the formulation−composition map. Recent findings are reported concerning the effect of variables with practical relevance (i.e., stirring energy, viscosity of phases, surfactant concentration, and partitioning) on the standard and dynamic inversion patterns. State-of-the-art emulsion inversion modeling is briefly discussed.

Current Phenomenological Know-How and Modeling of Emulsion Inversion

When polymer blends are prepared from a mixture of pellets, the melting order of the components is important in determining the mechanism of morphology development. Here, we show that an inversion of phase continuity occurs during processing when a minor phase component has a softening or melting transition temperature which is lower than the softening temperature of the major phase component. Three 80 :20 concentration systems were studied : polyarylate/rubber, polyamide 6,6/polystyrene, and polystyrene/ethylene propylene rubber. Initially, the minor phase was the continuous phase and coated the major phase in all three systems. As the major phase melted, a switching of phase continuity occurred, and in the final blend state, the major phase was the continuous phase. An increase in power input was required during the switching of the dispersed and matrix phases. The compounding process was studied through continuous video monitoring, torque-temperature analysis, and microscopy of quenched samples. A continuity inversion mechanism is proposed. It is found that the initial morphology of the blend consists of sheets of the major phase inside the minor phase. These sheets break up into irregularly shaped particles, which then coalesce around the minor phase. The effects of compatibilization (using reactive polymers or adding a premade diblock) on the rheology and morphology of the blend are also investigated. Interfacial reaction is seen to delay and intensify the inversion of phase continuity, whereas addition of premade diblock does not have any significant effect. The torque increases due to interaction of the major phase domains and due to reactive stabilization of the interface against coalescence, and the contributions of each to the torque can be decoupled.

Evidence for inversion of phase continuity during morphology development in polymer blending

http://www.firp.ula.ve/CV_profesores/86_JCIS_Anton.pdf

Emulsion instability in the three-phase behavior region of surfactant-alcohoi-oil-brine systems

Three protocols are tested to invert an abnormal emulsion into a normal one: a dynamic process with continuous addn. of an internal phase, continuous stirring of a given emulsion with no addn. of a ...

Emulsion Catastrophic Inversion from Abnormal to Normal Morphology. 4. Following the Emulsion Viscosity during Three Inversion Protocols and Extending the Critical Dispersed-Phase Concept

Surfactant-oil-water emulsified systems are found to exhibit a sharp change in viscosity near the optimum formulation for three-phase behavior. When the formulation is scanned through the three-phase transition by changing (in turn) brine salinity, oil EACN, surfactant HLB or alcohol concentration, the viscosity passes through a minimum for MOW three-phase emulsions. Bidimensional formulation scans corroborate that the viscosity minimum is associated with the optimum formulation. This minimum is related with the ultra-low interfacial tension exhibited by such systems.

I. Layrisse

Papers

Surfactant-oil-water systems near the affinity inversion part ii: viscosity of emulsified systems