Polymerization, latex

The section on suspension polymerization indicated the differentiation between suspension and emulsion (or latex) polymerizations. Emulsion polymers usually are formed with the initiator in the aqueous phase, in the presence of surfactants, and with polymer particles of colloidal dimensions, i.e., on the order of 0.1 gm in diameter [17]. Generally, the molecular weights of the polymers produced by an emulsion process are substantially greater than those produced by bulk or suspension polymerizations. The rate of polymer production is also higher. As a large quantity of water is usually present, temperature control is often simple. 

Preparation of Samples. PVC Latex. Polymerization was performed using chemical initiation (persulfate-metabisulfite) and radiochemical initiation (y-irradiation from 60Co mean dose rate 10,000 rads/hour). Emulsifier was potassium stearate. 

Utilizing the seed latex polymerization method to avoid the occurance of new particle formation, the kinetic treatment of an emulsion polymerization is quite straight forward. Assuming that all the particles are the same size, the rate of polymerization,... 

Figure 3, Conversion profiles for styrene seed latex polymerization at 50°C. Solid curves are theoretical predictions and data points are experimental results (( 3) < o = 0.0076 (A) a0 = 0.0393 (O )a0 = 0.458 (X) o = 137).

Quality Control of Latex Polymerization Using Hydrodynamic Chromatography. Latex polymers are most commonly manufactured in a large vessel with all the product being removed at the end of the polymerization reaction. This so-called batch polymerization process... 

Application of High-Speed, Integrated, Computerized, Hydrodynamic Chromatography for Monitoring Particle Growth During Latex Polymerization... 

In this publication monitoring of different particle growth patterns during latex polymerizations using the high speed computerized HDC will be described for S/B latexes. Kinetic information will not be dealt with in this paper. 

The second particle growth pattern was derived from a latex polymerization that was carried out using a simple electrolyte addition to the reactor. 

Figure 2. Conductivity vs. % conversion for latex polymerized with oleate soap...

Araki et at. (1967, 1969) carried out a more systematic study of the kinetics and other features of the y-iniliated emulsion polymerization of vinyl acetate using sodium lauryl sulfate as the emulsifier. This system had been thoroughly investigated with potassium persulfate as the initiator (Litt et cL. 1960,1970). Some post ei cts have been observed with vinyl acetate, particularly above 50% conversion (Friis, 1973 Sunardi, 1979). These effects had been used by Allen cr at. (1960,1962) for the possible synthesis of block and graft polymers and will be described later in this chapter. The half-life of the radicals in a vinyl acetate latex polymerization was determinad by Hummel et at. (1969) as 0.8 min at 53.8% conversion. Araki et fll. (1967, 1969) determined all the normal rate dependencies and included some seeded latex studies. Their results and those of other investigators are summarized in Table II together with those found with potassium persulfate initiation and those predicted by the Smith-Ewart Case 2 theory. The... 

In addition, VTMS hydrolyzes to a much eater extent than MTMS, an expected pattern similar to the /sopropoxy examples. Clearly the bulk of the Mopropoxy groups on the hindered silanes is very beneficial in protecting the silane from premature reaction during latex polymerization, when compared to the more traditional methoxy substituted silane monomers. This has implications for the ultimate properties of the final films, as the stability of the isopropoxy silanes allows levels of incorporation, and thus final performance, that are sinq)ly not available when using methoxy-substituted silane monomers. 

One volume part of triethanolamine with 5-7 parts of a mixture of CaOi and ZnOi is used as a filling material that enhances the restorative process in periodontal tissues. Triethanolamine is recommended as the preferred stabilizer to be used in latex polymerization because of its weak mutagenic effect in the Ames tests. 

Darathane . [WJk. Grace] Urethane prqpolymer dispersant, emulsifier latex polymerization. 

Effect of retardation by ethyl formate on the latex polymerization of vinyl acetate [223]. 

Use of ultrasound in latex polymerization of vinyl acetate copolymers [224]. 

Two general features of emulsion polymerization reaction systems for the production of carboxylated rubber latexes are of special interest The first b that the polymerization usually takes place under acidic conditions (c. pH 3-4) and not under the alkaline conditions which are usual for the production of non-functionalized synthetic rubber latexes. Polymerization is carried out under acidic conditions in order to encourage the carboxylic acid monomer to become copolymerized into the molecxiles of rubber being prcxluced. If the reaction is carried oui under alkaline conditions, then the carboxylic acid monomer is present mainly as a carboxylate salt which partitions strongly in favour of the aqueous phase If it polymerizes at all under these conditions, polymerization occurs mainly ir the aqueous phase of the reaction system, and the polymer molecxiles in whicl it becomes incorporated are far more hydrophilic than are the majority of the polymer molecxiles, which are produced in the latex particles. The requiremen... 

Uses Detergent, emulsifier for household and industrial cleaners and detergents, textile processing, paints, printing inks, agric., latex polymerization... 

---