Potassium persulfate initiation

The need for increased stabilities and for controllable permeabilities and morphologies led to the development of polymerized surfactant vesicles [55, 158-161]. Vesicle-forming surfactants haw been functionalized by vinyl, methacrylate, diacetylene, isocyano, and styrene groups in their hydrocarbon chains or headgroups. Accordingly, SUVs could be polymerized in their bilayers or across their headgroups. In the latter case, either the outer or both the outer and inner surfaces could be polymerized separately (Fig. 38). Photopolymerization links both surfaces selective polymerization of the external SUV surface is accomplished by the addition of a water-soluble initiator (potassium persulfate, for example) to the vesicle solution. 

Polymerization of styrene in each of the three types of microemulsions was performed using a water soluble initiator, potassium persulfate (K2S208), as well as an oil-soluble initiator, AIBN. As desired, solid polymeric materials were obtained instead of latex particles. In the anionic system, the cosolvent 2-pentanol or butyl cellosolve separates out during polymerization. Three phases are always obtmned after polymerization. The solid polymer was obtained in the middle with excess phases at the top and bottom. GC analysis of the upper phase indicates more than 80% 2-pentanol, while Karl-Fisher analysis indicated more than 94% water in the lower phase. Some of the initial microemulsion systems have either an excess organic phase on top or an excess water phase as the bottom layer. GC analysis showed the organic phase to be rich in 2-pentanol. However, the volume of the excess phase is much less in the initial system than in the polymerized system. 

Most emulsion polymerization is based on free-radical reactions, involving monomers (e.g., styrene, butadiene, vinyl acetate, vinyl chloride, methacrylic acid, methyl methacrylate, acrylic acid, etc.), surfactant (sodium dodecyl diphenyloxide disulfonate), initiator (potassium persulfate), water (18.2MQ/cm), and other chemicals and reagents such as sodium hydrogen carbonate, toluene, eluent solution, sodium chloride, and sodium hydroxide. 

Emulsion polymerization of methyl methacrylate under the action of pulsed microwave irradiation was studied by Zhu et al. [11], The reactions were conducted in a self-designed single-mode microwave reaction apparatus with a frequency of 1250 MHz and a pulse width of 1.5 or 3.5 ps. The output peak pulse power, duty cycles, and mean output power were continuously adjustable within the ranges 20-350 kW, 0.1-0.2%, and 2-350 W, respectively. Temperature during microwave experiments was maintained by immersing the reaction flask in a thermostatted jacket with a thermostatic medium with little microwave absorption (for example tetrachloroethylene). In a typical experiment, 8.0 mL methyl methacrylate, 20 mL deionized water, and 0.2 g sodium dodecylsulfonate were transferred to a 100-mL reaction flask which was placed in the microwave cavity. When the temperature reached a preset temperature, 10 mL of an aqueous solution of the initiator (potassium persulfate) was added and the flask was exposed to microwave irradiation. 

When the water-soluble initiator potassium persulfate is added to an emulsion polymerization system, it undergoes thermal decomposition to form sulfate radical anion ... 

Clay and mineral fillers have been used for reducing production costs and improving the comprehensive water absorbing properties of superabsorbent materials For example, a poly(acrylic acid)/mica superabsorbent has been synthesized with water absorbency higher than 1100 g H20/g In a typical method of preparation, acrybc acid monomer is neutralized at ambient temperature with an amount of aqueous sodium hydroxide solution to achieve 65% neutralization (optimum) Dry ultrafine (<0.2 tm) mica powder (10 wt%) is added, followed by cross-linker N,N-methylene-bisacrylamide (0.10 wt%) and radical initiator, potassium persulfate The mixture is heated to 60-70°C in a water bath for 4 h. The product is washed, dried under vacuum at 50°C, and screened. 

Sarkar el aL [6] studied the conventional thermal initiator, potassium persulfate. He discovered that the initial rate of potassium persulfate decomposition in the presence of VAc may be written as... 

In an in-situ encapsulation process, a dispersion including monomers and the pigment particles can be homogenized. The monomers in the dispersion are then polymerized at the surface of the pigment so as to encapsulate the pigment particles. 6-15% of the monomers are acidic. The acidic monomers can assist the pigment in remaining properly dispersed in the inkjet ink. As a polymerization initiator, potassium persulfate may be used (20). 

There are various additives in PVC plastics, such as antioxidants, light stabilizers, initiators, plasticizers, flame retardants, pigments and others. As initiators, potassium persulfate, benzoyl peroxide, lauryl peroxide, percarbonate and some azo-compounds can be used. The presence of chlorine in the hydrocarbon backbone gives rigidity and toughness to the polymer, but PVC liberates hydrogen chloride when exposed to high temperatures. To prevent this, stabilizers are added to the polymer. There are several kinds of stabilizers on the market. The most important contain lead, tin, calcium and zinc and... 

Cho and Lee [6] used three different initiators, potassium persulfate, 2,2 -azobisisobutyronitrile, and 4,4 -azobis(4-cyanovaleric acid) (water-soluble, but less hydrophilic than potassium persulfate) to investigate their effects on the emulsion polymerization of styrene in the presence of polymethyl methacrylate seed latex particles. Inverted core/shell latex particles were observed when 2,2 -azobisisobutyronitrile or 4,4 -azobis(4-cyanovaleric acid) was used to initiate free radical polymerization. The use of potassium persulfate resulted in various morphological structures of latex particles, which were largely determined by the initiator concentration and polymerization temperature. 

Figure 8.2. Profiles of the calculated average number of free radicals per particle (n, or n ) as a function of monomer conversion for the experiment at SCC with the weight fractions of polystyrene seed particles (154nm in diameter), the second-stage monomer (methyl methacrylate), and the weight fraction of initiator (potassium persulfate) equal to 0.06, 0.09, and 9.62 X 10 , respectively.

Bentonite enriched in montmorillonite with 75meq/100g of cation exchange capacity, as determined in this laboratory, was provided by Linan Chemical Factory of Bentonite of Zhejiang Province. Ethyl acrylate monomer was purified by distillation under reduced pressure before use. All the water used was deionized. The initiator potassium persulfate (KPS) and the surfactant sodium dodecylsulphate (SDS) were used as supplied. 

FIG. 10 Continuous macroemulsion and miniemulsion polymerization of methyl methacrylate. Continuous (stirred tank) macro- and miniemulsion polymerization of methyl methacrylate at 40°C in a surfactant (SLS) concentration of 0.67 wt% (based on monomer). Cosurfactant (miniemulsion only) 2 wt% (based on monomer). Initiator potassium persulfate 0.01 M. Total solids 31 wt%. (From Ref. 85, with permission from Elsevier Science.)... 

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