Emnlsion polymerization

Poehlein GW. Emnlsion polymerization in continnons reactors. In Piirma I, editor. Emulsion Polymerization. New York Academic Press 1982. p 357. 

The emnlsion polymerization process is similar to snspension polymerization. This process is also carried out in a water medinm. An emulsifier, either anionic soap or cationic soap, is added to break the monomer into very small particles. The initiator is in solution in the water. After polymerization, the polymer can be precipitated, washed, and dried, or the mix-tnre can be used directly (e.g., latex paint). 

FIGURE 14.12. Polymer-surfactant interactions are important in many areas of polymer science and technology, especially emnlsion polymerization. In snch processes surfactants and micelles perform several dnties snch as emulsification of monomers (a), solnbihzation of growing oUgomeric free radical chains (b), and stabilization of growing and final polymer particles (c). 

Reactors for the emnlsion poljunerization of methacrylic esters are made of stainless steel and are jacketed for temperature control these reactors are bnilt to withstand pressnres of 446 kPa (65 psi) and contain emergency stacks with rupture disks in case of excess pressure buildup within the reactor. Agitation is a critical issne for emnlsion polymerization. Variable-speed drive shafts are used along with stainless steel agitators to mix the batch. Baffles on the reactor walls are also common featnres of indnstrial emulsion polymerization reactors. Temperature control is maintained through the use of steam and cold water circulation with the jacket of the reactor. Feed lines for the monomer emulsion, initiators, and... 

Redox initiator systems are normally used in the emnlsion polymerization of VDC to develop high rates at low temperatures. Reactions mnst be carried out below 80°C to prevent degradation of the polymer. Poly(vinylidene chloride) in emulsion is also attacked by aqueons base. Therefore, reactions shonld be carried out at low pH. 

The polymerization rate in emnlsion polymerization is significantly higher than in bnlk polymerization. In a latex, the overall concentration of radicals increases as the number of particles increases, for example, by decreasing the particle size at a given solids content. This provides fnrther means of increasing polymerization rate (in addition to increasing temperature and initiator concentration). 

Penlidis A, MacGregor JF, Hamielec AE. A theoretical and experimental investigation of the batch emnlsion polymerization of vinyl acetate. Polym Proc Eng 1985 3 185-218. 

Gughotta LM, Leiza JR, Arotcarena M, Armitage PD, Asua JM. Copolymer composition control in nnseeded emnlsion polymerization using calorimetric data. Ind Eng Chem Res 1995 34 3899-3906. 

Alb AM, Reed WF. Simultaneous monitoring of polymer and particle characteristics during emnlsion polymerization. Macromolecnles 2008 41 2406-2414. 

FIGURE 18.1 Mechanisms occurring in emnlsion polymerization. From Zeaiter J. A framework for advanced/inteUigent operation of emulsion polymerization reactors [PhD Thesis]. Sydney University of Sydney 2002. 

Nestor, J., Esquena, J., Solans, C. et al. (2005) Emnlsion polymerization of styrene and methyl methacrylate using a hydrophobically modified inulin and comparison with other surfactants. Langmuir, 21 (11), 4837-4841. 

O Mealey et al. (2006) studied the effect of microwave irradiation (mnltimode microwave reactor) on the emulsion polymerization of styrene and methyl meth-aciylate. The emnlsion polymerization of methyl methacrylate was faster with microwave irradiation. It was observed that the obtained molecular weights for polystyrene and poly(methyl methacrylate) were higher when the polymerization was performed under microwave irradiation It was ascribed to higher degree of branching, when microwave irradiation was applied. 

The simplest way to make a polymer nanoeomposite via inverse emulsion polymerization is to mix the water-solnble monomer and hydrophilic nanoparticles together in the water as a dispersed phase. Kim et al. prepared intercalated condueting polypyrrole (PPy)/Na -MMT nanoeomposite by inverse emnlsion polymerization. They followed a similar preparation method... 

Comparison with Conventional Emnlsion Polymerization. Let us eonsider two series of experiments with different KPS concentrations. One of these series is a conventional emulsion polymerization (involving a surfactant) and the second is a soap-free proeess involving Laponite and PEGMA. 

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