Dispersion polymerization recipes

Some typical dispersion polymerization recipes and the electron micrograph of the uniform polymeric particles with Recipe I are given in Table 5 and Fig. 10, respectively. As seen in Table 5, the alcohols or alcohol-water mixtures are usually utilized as the dispersion media for the dispersion polymerization of apolar monomers. In order to achieve the monodispersity in the final product, a costabilizer can be used together with a primary steric stabilizer, which is usually in the polymeric form as in... 

Table 5 Typical Dispersion Polymerization Recipes Providing Uniform Latex Particles...

Many suspension polymerization recipes have been reported/75 Some of the more successful that yield polymers of low dispersity are for MMA with 146, S, BA, MA, tBA and copolymers with 154,j7/ and BMA with I38/21 Important considerations are a catalyst that is both hydrophobic (to limit partitioning into the aqueous phase) and hydrolytically stable. 

A typical emulsion polymerization recipe includes specific proportions of the added ingredients, e.g. (in wt%) monomer, 100 water, 150 initiator, 0.5 surfactant, 5. Because the monomer has low water solubility, it is clear that there will be two separate phases referred to as the monomer phase and the aqueous phase. The aqueous phase, containing the surfactant in the form of micelles, can be considered as consisting of two phases, the micellar phase and the true aqueous phase. The emulsifier helps disperse the monomer in the aqueous phase with droplets in the order of a few micrometers in size. The hydrophobic interior of the micelles contains solubilized monomer, which is apportioned by diffusion out of the emulsified monomer droplets and through the aqueous phase. 

The minimum requirements for a dispersion polymerization are monomer, solvent/nonsolvent, initiator, and steric stabilizer. The monomer must be soluble in the reaction mixture and its polymer, insoluble. The monomers used in systems of commercial interest are methyl methacrylate, vinyl chloride, vinyli-dene chloride, vinyl esters, hydroxyl alkyl acrylates. A typical recipe for dispersion polymerization is shown in Table 9. 

Unlike PIC, which requires a precast structure, PCC has the advantage that it can be cast in place for field applications. Most of the PCC composites are based on different kinds of lattices obtained especially by emulsion polymerization. A latex is a stable dispersion of fine polymer particles in water, also containing some nonpolymeric constituents used in emulsion polymerization recipe. The lattices obtained through emulsion polymerization contain small polymer particles of 0.05-5 tm. 

The physical picture of emulsion polymerization is based originally on the qualitative picture of Harkins [18] and the quantitative treatment of Smith and Ewart [19], followed by other contributions. Gilbert shaped the qualitative and quantitative picture of the emulsion polymerization process as it is now generally accepted [16]. The main components of an emulsion polymerization recipe are the monomer(s), dispersing medium (usually water), surfactant and initiator. 

Other Components. The smaller the particle size, at a given phase ratio, the more difficult it is to ensure colloidal stability (cf Fig. 5). This means that for aqueous heterophase polymerizations in the order suspension < microsuspension < emulsion < miniemulsion < microemulsion, the stabilizer concentration increases. Contrary to the simple polymerization of st5Tene in water, polymerization recipes for industrially important polymer dispersions comprise up to six monomers, frequently more than two emulsifiers, more than one initiating system, and a few other aids like biocides, defoaming agents, plasticizers for supporting film formation (39). The monomer-to-water ratio is adjusted in such a way that a solid content results typically between 40 and 60% or even higher. The amoimts of surfactants and initiator (mainly peroxodisulfate) are typically between 0.5 and 2% (w/w) relative to the monomers and 0.5% (w/w) relative to water, respectively. 

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. 

Typical Recipes for Dispersion Polymerizations of e-Caprolactone and Lactide 649... 

Since in dispersion polymerization of cyclic esters, some experimental details are crucial for obtaining product in the form of suspension of microspheres free of their aggregates, brief recipes for synthesis of poly(D,L-lactide) and PCL microspheres are given below. These recipes are based on experiments described in Reference 10. 

The composition of the dispersion agents, which are produced in dedicated reactors, is the same for all recipes. The batch sizes may be one or two polymerization batch units for Dl and one, two, three or four polymerization batch units for D2. The processing times are ten hours for Dl and two hours for D2, and they do not depend on the batch sizes. The dispersion agents in their final states are unstable in the reactors and stable for limited periods of time in the storage... 

The physical picture of emulsion polymerization is based on the original qualitative picture of Harkins [1947] and the quantitative treatment of Smith and Ewart [1948] with subsequent contributions by other workers [Blackley, 1975 Casey et al., 1990 Gao and Penlidis, 2002 Gardon, 1977 Gilbert, 1995, 2003 Hawkett et al., 1977 Piirma, 1982 Poehlein, 1986 Ugelstad and Hansen, 1976]. Table 4-1 shows a typical recipe for an emulsion polymerization [Vandenberg and Hulse, 1948]. This formulation, one of the early ones employed for the production of styrene-1,3-butadiene rubber (trade name GR-S), is typical of all emulsion polymerization systems. The main components are the monomer(s), dispersing medium, emulsifier, and water-soluble initiator. The dispersing medium is the liquid, usually water,... 

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