Emulsion polymerization of styrene

In addition to appHcations in dyeing, sodium formaldehyde sulfoxylate is used as a component of the redox system in emulsion polymerization of styrene—butadiene mbber recipes. 

Figure 2 A typical scanning electron micrograph of the submicron size (0.2 / tm), uniform polystyrene micro-spheres produced by the emulsion polymerization of styrene. Magnification 20,000 x.

The polymerization reaction is conducted at the desired temperature with a slow stirring regime for a certain period. A typical recipe for the emulsion polymerization of styrene is exemplified in Table 1 [40]. As seen here, potassium persulfate and sodium dodecyl sulfate were used as the initiator and the stabilizer, respectively. This recipe provides uniform polystyrene particles 0.22 /Lim in size. 

Table 1 A Typical Recipe for the Emulsion Polymerization of Styrene [40]...

Flgure 4 The effect of initiator concentration on the variation of monomer conversion by the polymerization time in the emulsion polymerization of styrene. Styrene-water = 1/3 SDS = 15.4 mM reaction volume = 300 ml stirring rate = 250 rpm temperature = 70°C. 

Based on the Smith-Ewart theory, the number of latex particles formed and the rate of polymerization in Interval II is proportional with the 0,6 power of the emulsifier concentration. This relation was also observed experimentally for the emulsion polymerization of styrene by Bartholomeet al. [51], Dunn and Al-Shahib [52] demonstrated that when the concentrations of the different emulsifiers were selected so that the micellar concentrations were equal, the same number of particles having the same size could be obtained by the same polymerization rates in Interval II in the existence of different emulsifiers [52], The number of micelles formed initially in the polymerization medium increases with the increasing emulsifier concentration. This leads to an increase in the total amount of monomer solubilized by micelles. However, the number of emulsifier molecules in one micelle is constant for a certain type of emulsifier and does not change with the emulsifier concentration. The monomer is distributed into more micelles and thus, the... 

Medvedev et al. [57] extensively studied the use of nonionic emulsifiers in emulsion polymerization. The emulsion polymerizations in the presence of nonionic emulsifiers exhibited some differences relative to those carried out with the ionic ones. Medvedev et al, [57] proposed that the size of latex particles remained constant during the reaction period, but their number increased continually with the increasing monomer conversion. The use of nonionic emulsifiers in emulsion polymerization usually results in larger sizes relative to those obtained by the ionic emulsifiers. It is possible to reach a final size value of 250 nm by the use of nonionic emulsifiers in the emulsion polymerization of styrene [58]. 

All these effects increase the overall polymerization rate and decrease the degree of polymerization. The effect of polymerization temperature on the variation of monomer conversion with the polymerization time is exemplified in Fig. 8 for the emulsion polymerization of styrene. 

Sheu and coworkers [111] produced polysty-rene-polydivinylbenzene latex interpenetrating polymer networks by the seeded emulsion polymerization of styrene-divinylbenzene in the crosslinked uniform polystyrene particles. In this study, a series of uniform polystyrene latexes with different sizes between 0.6 and 8.1... 

In another study, uniform composite polymethyl-methacrylate/polystyrene (PMMA/PS) composite particles in the size range of 1-10 fim were prepared by the seeded emulsion polymerization of styrene [121]. The PMMA seed particles were initially prepared by the dispersion polymerization of MMA by using AIBN as the initiator. In this polymerization, poly(7V-vinyl pyrolli-done) and methyl tricaprylyl ammonium chloride were used as the stabilizer and the costabilizer, respectively, in the methanol medium. Seed particles were swollen with styrene monomer in a medium comprised of seed particles, styrene, water, poly(7V-vinyl pyrollidone), Polywet KX-3 and aeorosol MA emulsifiers, sodium bicarbonate, hydroquinone inhibitor, and azobis(2-methylbu-... 

Continuous-Emulsion Polymerization of Styrene in a Tubular Reactor... 

The work reported here is part of a continuing program on the emulsion polymerization of styrene in a tubular reactor. It is now evident that the reactor construction is of primary importance in avoiding the problem of reactor plugging. The plugging is associated with a wall effect so that both the reactor dimensions and the nature of the wall surface are important. 

The synthetic route for making the Janus nanoparticles first consists in the emulsion polymerization of styrene in the presence of silica nanoparticles surface-modified by polymerizable groups. Snowman-like hybrid nanostructures are thus obtained with 85% yield in which the... 

TABLE 4-1 Composition of a GR-S Recipe for Emulsion Polymerization of Styrene-Butadiene"... 

Fig. 4-3 Plot of percent conversion versus time for emulsion polymerizations of styrene with different concentrations of potassium laurate at 60° C. The moles of emulsifier per polymerization charge (containing 180 g H2O, 100 g styrene, 0.5 g K2S2O8) are 0.0035 (plot 1), 0.007 (plot 2), and 0.014 (plot 3). After Williams and Bobalek [1966] (by permission of Wiley-Interscience, New York).

Figure 4-5 shows the viscosity-average molecular weights in the emulsion polymerizations of styrene of Fig. 4-3. The results are in line with Eq. 4-7 in that the polymer size increases with the emulsifier concentration.

The typical emulsion polymerization of styrene was confirmed to proceed in Case 2. According to Eq. (I), the rate constant of propagation can be calculated by measuring the rate of polymerization (Rp) and the number of particles (N) and substituting 0.5 for n. 

First stage of polymerization emulsion polymerization of styrene, hydroxye-thyl methacrylate, and acrylic acid in the presence of isooctane. 

The following experiment describes the background of free radical polymerizations of vinyl monomers. This information will be experimentally illustrated in experiments involving bulk and emulsion polymerizations of styrene. 

A. W. De Graff, Continuous Emulsion Polymerization of Styrene in a One Stirred Tank Reactor. Lehigh Univ. Press, Bethlehem, PA, 1970. 

Observations Emulsion polymerization of styrene has been used to prepare a latex for... 

Reaction Rate—Time Curves. In papers on the emulsion polymerization of styrene generally the classic curve is shown. The three reaction periods of this curve, according to Harkins, Smith, and Ewart (6) can be interpreted as ... 

In the first step a rubbery polymer latex is prepared by emulsion polymerization of styrene and butadiene, the styrene being in an amount of 25%. Divinylbenzene is added as crosslinking agent in an amount of 1%. Diphenyl oxide sulfonate is used as emulsifier in aqueous solution and sodium formaldehyde sulfoxylate acts as a buffer in order to reach a pH of 4. As radical initiator, cumene hydroperoxide is used and the polymerization is conducted 70°C for 9 h. The end of the reaction period is detected as no further pressure drop is observed due to the consumption of butadiene. 

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