Emulsifier initiator

As mentioned earlier, the necessary components for emulsion polymerization are monomer, emulsifier, initiator, and water. The monomer is insoluble in water in principle, although a small amount of water-soluble monomer can be used as a comonomer in some practical cases. On the other hand, the initiator is usually water soluble. These relations mean that the loci for radical formation and radical polymerization are different, that is, in aqueous and organic phases, respectively. This might look irrational, but the unique advantages of emulsion polymerization lie in it. When radicals are formed from a water-soluble initiator in an aqueous medium in Figure 11.1.2, top, left, each radical undergoes one of the following reactions ... 

The surface of polymer particles obtained by emulsion polymerization is occupied by emulsifier molecules, initiator fragments, and hydrophilic comonomer units. Therefore, desirable design of the surface ought to be done by choosing the emulsifier, initiator, and comonomer. Some of them are employed in aiming for postreaction at the surface to convert it into a functional one. When any change is necessary on the particle surface, modification of surface can be done by the following means ... 

Latex Emulsifier Initiator Buffer Sulfate Carboxyl PH... 

Ozdeger et al. studied the role of the nonionic emulsifier Triton X-405 (octyl-phenoxy polyethoxy ethanol) in the emulsion homopolymerization of St [99] and n-butyl acrylate (n-BA) [ 100], and in the emulsion copolymerization of St and n-BA [101]. In the emulsion homopolymerization of St, they noted two separate nucleation periods, resulting in bimodal PSDs. Although the total concentration of the emulsifier was maintained at a level above its CMC based on the water phase in the recipe, the portion of the emulsifier initially present in the aqueous phase was below the CMC due to partitioning between the oil and aqueous phases. Due to the nature of this emulsifier, the first of the two nucleation periods was attributed to homogeneous nucleation, while the second was... 

The average degree of polymerization is independent of the reaction variables such as the emulsifier, initiator, monomer concentrations eind the number of polymer particles. 

Polymerization. The polymerizations were carried out in a 4C liter reactor. Water, emulsifier, initiator and buffer were charged, de-aeration followed, and monomer was added. Then the reaction was started by raising the temperature of the batch... 

Keywords Antioxidants, Emulsifiers, Initiators, Integrated product policy. Lubricants, Plasticizers, Polymerization, Protective colloids. Renewable resources. Stabilizers, Surfactants, Sustainability... 

In a typical emulsion polymerization, emulsifier, initiator, and buffer are dissolved in deionized water and are fed continuously to... 

Organic phase Emulsifier Initiator Phase ratio (Water Oil) Emulsifier concentration (wt % of organic phase) Monomer concentration (wt % of aqueous phase) Temperature (°C) Reference Characteristics of the polymerization Polymerization domain... 

In the semicontinuous process, the reactor is initially charged with a fraction of the formulation (monomers, emulsifiers, initiator and water). The initial charge is polymerized in batch for some time and then the rest of the formulation is added over a certain period of time (typically 3—4 h). The monomers can be fed either as an aqueous pre-emulsion sta-bihzed with some emulsifier or as neat monomers. Monomers contain inhibitors to allow safe storage and they are used without purification. The initiator is fed in a separate stream. The goal of the batch polymerization of the initial charge is to nucleate the desired number of polymer particles. Because particle nucleation is prone to suffer run-to-run irreprodu-cibility, seeded semicontinuous emulsion polymerization is often used to overcome this problem. In this process, the initial charge contains a previously synthesized latex (seed) and eventually a fraction of the formulation (monomers, emulsifiers, initiator and water). Therefore, nucleation of new particles is minimized leading to better reproducibility. 

In emulsion pol)rmerizations, the dispersion medium, for monomer droplets and pol)rmer particles, is generally water as well as liquids other than water. Water is cheap, inert and environmentally friendly. It provides an excellent heat transfer and low viscosity. It also acts as the medium of transfer of monomer from droplets to particles, the locus of initiator decomposition and oligomer formation, the medium of dynamic exchange of emulsifier between the phases, and the solvent for emulsifier, initiator, and other ingredients. 

The semi-continuous emulsion polymerization processes is characterized by continued addition of reaction ingredients such as monomer, emulsifier, initiator, or water to the reaction system throughout the polymerization. In this emulsion polymerization process, two major types of feeds are used for the introduction of ingredients to the reactor neat monomer feed (M) or monomer emulsion feed (ME). In M feed method, the feed contains only monomer and all the other ingredients are initially in the reactor. Otherwise, the major components of the ME feed are a monomer, a part from the emulsifier, and water. But it... 

The raw materials required for the production of polycarboxylates using the emulsion polymerization process are water, monomers, emulsifiers, initiators, and if required, modifiers. 

The reaction is conducted by introducing the butadiene monomer, emulsifier, initiator, and chain transfer agent into the batch reactor and then elevating the temperature while stirring the reaction mixture. The ratio of butadiene to water is generally about 1 1. The emulsifier is added in the ratio of about 1 to 5 parts with respect to 100 parts of butadiene monomer, and it is used in the form of the salt of rosin or fatty soap. After the grafting reaction, the emulsifier, which can have the agglomerating property for acid or salt, is used. 

The preparation of polymer colloids is both a science and an art. It is a science in which the kinetic principles of free radical-initiated vinyl addition polymerization are superimposed on the heterogeneous polymer latex system. It is an art in that the preparer uses a recipe which comprises monomer, water, emulsifier, initiator, and other ingredients, and the quality of the latex obtained depends upon small variations in the polymerization parameters as well as the skill of the preparer. The purpose of this paper is to review the different types of polymer latexes and the mechanisms proposed for their preparation, and to give examples of the preparation of different types. 

Tabk 9. Variation of the rate of polymerization with concentration of emulsifier, initiator and monomer ... 

In the second chapter (Preparation of polymer-based nanomaterials), we summarize and discuss the literature data concerning of polymer and polymer particle preparations. This includes the description of mechanism of the radical polymerization of unsaturated monomers by which polymer (latexes) dispersions are generated. The mechanism of polymer particles (latexes) formation is both a science and an art. A science is expressed by the kinetic processes of the free radical-initiated polymerization of unsaturated monomers in the multiphase systems. It is an art in that way that the recipes containing monomer, water, emulsifier, initiator and additives give rise to the polymer particles with the different shapes, sizes and composition. The spherical shape of polymer particles and the uniformity of their size distribution are reviewed. The reaction mechanisms of polymer particle preparation in the micellar systems such as emulsion, miniemulsion and microemulsion polymerizations are described. The short section on radical polymerization mechanism is included. Furthermore, the formation of larger sized monodisperse polymer particles by the dispersion polymerization is reviewed as well as the assembling phenomena of polymer nanoparticles. 

---