Monomer/water ratio

Fig. 4-4 Plot of percent conversion versus time for emulsion polymerization of vinyl chloride at 50°C for monomer/water ratio of 26/74 and 0.883% surfactant. The initiator concentrations are 0.0012% (plot 1), 0.0057% (plot 2), and 0.023% (plot 3). After Vidotto et al. [1970] (by permission of Huthig and Wepf Verlag, Basel, and Wiley-VCH, Weinheim).

Thomas and Webb (129), using an emulsion polymerization model, calculated k2 from Rp and the number of particles. Their value at room temperature was 2 x 104 1 m-1l-1, in good agreement, perhaps fortuitously, with Dainton and Eaton (49). This treatment assumes that the monomer water ratio at the particle is the same as in the continuous phase. If allowance were made for adsorption of monomer this value of k2 would fall to approach more closely the level observed in DMF. 

The experimental factors that affect the stability of the latex during and after polymerization are the recipe used for the polymerization, the type and intensity of agitation during and after the polymerization, the temperature of polymerization and storage, and the age and storage conditions of the latex. The recipe used in the polymerization included the mode of polymerization, the monomer-water ratio, the solubility of the monomer in water, the emulsifier type and concentration, initiator type and concentration, total electrolyte concentration, and impurities present in the system. 

Figure 8. Rate of particle formation (dNp/dt) vs. polymerization rate at 20% conversion for various amounts of SDS (-%-) or monomer/water ratio ( X )...

Base case parameters temperature=50 °C monomer/water ratio=0.4 g/g surfactant CMC= 0.004 mol/L(aq) surfactant concentration=0.020 mol/L surfactant surface area=0.57 nmV molecule molecules per micelle=62 monomer watersaturation=0.137 mol/L(aq)... 

The molecular weight of the polyvinyl chloride appears to be mainly governed by chain transfer to monomer. The molecular weights at a number of conversions, dose rates, monomer-water ratios, and soap concentrations are presented in Table I and appear to be little affected by the reaction variables. The mean number average molecular weight is 1.25 x 10 close to that calculated from the reported values for chain transfer to monomer at 25 C (12). 

The influence of the monomer to water ratio on the polymerization rate was studied with sodium lauryl sulfate as the emulsifier. The conversion curves for the case of 3% emulsifier are shown in Figure 5. In Figure 6 the linear conversions for ten minutes of irradiation at 0.175 Mrads per hour are plotted against the water-monomer ratio for 1, 3, and 5% emulsifier. All three sets of data show a linear dependence of the rate on the ratio, in other words, the rate per cubic centimeter of water phase is independent of the monomer-water ratio. 

Two of us proposed that in the reaction of (i-C4H9)3Al with H2O, the active initiator is formed and that for every active site approx, ten molecules of H2O are used. This latter proposal came from comparison of DP of resulting polymers and starting [monomer]/[water] ratio. Thus, the initiating species has the structure ... 

Aqueous emulsions of styrene, methyl methacrylate, methyl acrylate, and ethyl acrylate were polymerized with y-radiation from a Co source in the presence of sodium dodecyl sulfate or sodium laurate. The continuous measurement of conversion and reaction rate was carried out dilato-metrically. The acrylates polymerized fastest and the over-all polymerization rate increased as follows styrene < methyl methacrylate < ethyl acrylate methyl acrylate. The effects of radiation dose, temperature, and original monomer and emulsifier concentrations were studied with respect to the following factors properties of polymer dispersions, number and size of polymer particles, viscometrically determined molecular weights, monomer-water ratio, and kinetic constants. 

Our assumption of prolonged particle formation during the emulsion polymerization of MA can explain the course of v r in mixtures with high emulsifier concentration. For proving this assumption it would be necessary to measure the change in particle number during the course of the emulsion polymerization of MA this has not yet been done. The results of our work on the y-induced emulsion polymerization of MA cannot be interpreted in terms of the Smith-Ewart theory in its simple form (33). Therefore one cannot expect that v r is independent of the monomer-water ratio or proportional to [E] - or to [initator] - (dose rate and initator concentration can be substituted). A quantitative interpretation of the y-induced emulsion polymerization of MA cannot yet be formulated, because of the complexity of the phenomena involved. To make this possible, considerable further work on this subject has to be done. The dependence of on [M] - ... 

Figure 8.4 Comparison between experimoital and model results for vinyl acetate emulsion polymerization. Comprehensive model, T = 50°C, monomer/water ratio = 0.4, Agitator speed = 320 rpm. [14]...

For initiation in the aqueous phase to produce a monodisperse latex, the primary particles generated early in the reaction must act as nuclei to capture all primary radicals formed thereafter and these nuclei must grow without flocculation until the end of the polymerization. Therefore, the emulsifier must adsorb rapidly enough to stabilize these initial nuclei but not so rapidly as to stabilize the primary particles formed later in the reaction. This condition may be met if the emulsifier concentration is relatively low or if the emulsifier is omitted the sulfate endgroups introduced by the persulfate initiator are often sufficient to stabilize latex particles at relatively low monomer-water ratios (30). Table III gives the increase in particle size and surface charge resulting from the flocculation of the primary particles described in... 

The data used to illustrate emulsion polymerization at high Reynolds numbers were those of Ruben (17) 65 35 vinyl chloride-ethyl acrylate copolymers were prepared using a 40-50 60-50 monomer water ratios, 9.2% hydrocarbon sulfonate and 2.3% polyoxyethylated phenol emulsifiers, 0.57% ammonium persulfate initiator, and 0.40% sodium acetate buffer. The polymerizations were carried out in a 2-gallon jacketed stainless steel reactor equipped with a 2-, 3-, or 4-inch flat-blade impeller at pressures less than 110 psi, for 4 hours at 52°, 2 hours at 54°, and 3 hours at 60°. Figure 11 shows... 

A typical monomer/water ratio in suspension processes ranges from 1/4 to 1/1 and the particle size ranges from 0.1 to 1.0 mm. After polymerization, the polymer beads are washed with acid to remove initiator residue... 

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