Initiators ammonium persulfate

Data of Badder and Brooks (24). Figure 7 shows the comparisons of EPM with the experimental data obtained by Badder and Brooks (2A) in a CSTR (run C-24). The reactor feed contained 22.8% styrene, 0.64% emulsifier (sodium dodecylsulfate), and 0.39% initiator (ammonium persulfate). The residence time was 114 min. The initial reactor charge was water and emulsifier. In this case the size of the primary precursors was varied slightly from its baseline value of 1 nm to 0.8 nm. Although the experimental data show some scatter, EPM reproduces very well both the transient and steady state... 

Figure 6. Example data acquisition for the continuous emulsion polymerization of MM A showing conversion and surface tension oscillations (Run 15, Recipe 8 T = 40°C initiator (ammonium persulfate) =0.01 gmol/L H20 emulsifier (SLS) = 0.02 gmol/L H20 wt. ratio monomer/water = 0.43)...

Procedure 5-10 is an adaption of a ter-polymerization that starts with the formation of a seed latex followed by the gradual addition of both a monomer composition and an initiator solution at separate rates. The resulting latex has a high percentage of non-volatiles. It is said to be suitable for formulating good emulsion paints. In connection with this preparation, care must be taken that the initiating ammonium persulfate is indeed active. 

Polystyrene colloids (PS) were synthesized by soap-less emulsion polymerization [5, 33, 34]. This prevents desorption of surfactant from the surface with time, resulting in better defined surface properties. The colloids were synthesized in presence of acrylic acid as co-monomer and the anionic radical initiator ammonium persulfate was used to start the reaction. Above a certain size the colloids are electrostatically stabilized. Since acrylic acid is a weak acid, its negative charge is pH dependent. Emulsion co-polymerization of styrene with small amounts of acrylic acid results in poly(styrene-co-acrylic acid) polymer chains provides a steric stabilization as the chains are partially situated at the water-colloid interface [35, 36]. 

In a typical adiabatic polymerization, approximately 20 wt % aqueous acrylamide is charged into a stainless steel reactor equipped with agitation, condenser, and cooling jacket or coils. To initiate the polymerization, an aqueous solution of sodium bisulfite [7631-90-5] is added, followed by the addition of a solution of ammonium persulfate [7727-54-0] N2HgS20g. As the polymerization proceeds, the temperature rises to about 90°C, and then begins to fall at the end of the polymerization. The molecular weight obtained depends primarily on the initiator concentration employed. 

Isothermal polymerizations are carried out in thin films so that heat removal is efficient. In a typical isothermal polymerization, aqueous acrylamide is sparged with nitrogen for 1 h at 25°C and EDTA (C2QH2 N20g) is then added to complex the copper inhibitor. Polymerization can then be initiated as above with the ammonium persulfate—sodium bisulfite redox couple. The batch temperature is allowed to rise slowly to 40°C and is then cooled to maintain the temperature at 40°C. The polymerization is complete after several hours, at which time additional sodium bisulfite is added to reduce residual acrylamide. 

Thermally activated initiators (qv) such as azobisisobutyroaittile (AIBN), ammonium persulfate, or benzoyl peroxide can be used in solution polymeriza tion, but these initiators (qv) are slow acting at temperatures required for textile-grade polymer processes. Half-hves for this type of initiator are in the range of 10—20 h at 50—60°C (13). Therefore, these initiators are used mainly in batch or semibatch processes where the reaction is carried out over an extended period of time. 

The most common water-soluble initiators are ammonium persulfate, potassium persulfate, and hydrogen peroxide. These can be made to decompose by high temperature or through redox reactions. The latter method offers versatility in choosing the temperature of polymerization with —50 to 70°C possible. A typical redox system combines a persulfate with ferrous ion ... 

Recently, Si et al. [59,60] have investigated the synthesis of polymerizable amines, such as N-(3-dimethyl-aminopropyl) acrylamide(DMAPAA) and N-(3-dimeth-ylaminopropyl) methacrylamide (DMAPMA), and their copolymerization reaction. DMAPAA or DMAPMA in conjunction with ammonium persulfate was used as a redox initiator for vinyl polymerization. Copolymers having amino pendant groups, such as copolymer of... 

Normally, persulfate (41) can only be used to initiate polymerization in aqueous or part aqueous (emulsion) media because it has poor solubility in most organic solvents and monomers. However, it has been reported that polymerizations in organic solvent may be initiated by crown ether complexes of potassium persulfate.234 237 Quaternary ammonium persulfates can also serve as useful initiators in organic media. 4 The rates of decomposition of both the crown ether complexes and the quaternary ammonium salts appear dramatically... 

Figure 5 shows that EPM is able to reproduce fairly well the experimentally observed dependence of the particle number on surfactant concentration at a fixed initiator concentration (ammonium persulfate =... 

As an even more explicit example of this effect Figure 6 shows that EPM is able to reproduce fairly well the experimentally observed dependence of the particle number on surfactant concentration for a different monomer, namely methyl methacrylate (MMA). The polymerization was carried at 80°C at a fixed concentration of ammonium persulfate initiator (0.00635 mol dm 3). Because methyl methacrylate is much more water soluble than styrene, the drop off in particle number is not as steep around the critical micelle concentration (22.) In this instance the experimental data do show a leveling off of the particle number at high and low surfactant concentrations as expected from the theory of particle formation by coagulative nucleation of precursor particles formed by homogeneous nucleation, which has been incorporated into EPM. 

Due to the low solubility of the monomer 1III) in benzene, the polymerization had to be carried out at less than 10% (w/v) monomer concentration. A yield of 92% was obtained by AIBN initiation at 60°C. Ammonium persulfate and benzoyl peroxide initiators were found to be ineffective. The solubility characteristics of poly(N-pheny1-3,4-dimethylenepyrroline) are listed in Table I. The polymer was insoluble in most common solvents except for formic acid and trifluoroacetic acid. The polymer was characterized by C,H elemental analysis, IR and NMR. 

An alternative method of preparing the saturated cyclic amines via cyclopolymerization of diallylamine or diallylammonium chloride was unsuccessful. Common free radical initiators such as 2,2 -azobisisobutyronitrile, ammonium persulfate, benzoyl peroxide were found to be ineffective. Several procedures reported in the literature were followed, and unfortunately all of them have resulted only a small amount of low molecular weight oligomers. Further research for polymerization conditions and types of initiation is still required. 

An account of a serious warehouse explosion (15 dead, 141 injured). The two principal detonations were mostly due to ammonium nitrate, of which some hundred tonnes had been present, but the initiating fire was first observed in ammonium persulfate. This had been promiscuously stored alongside potassium permanganate, matches, potassium nitrate and sodium sulphide (or possibly sulphite), inter alia. None of these would improve the safety of ammonium persulfate. It was shown that the persulphate gives an immediate exothermic reaction with the sulphide. This was ascribed as the ultimate initiation. It was concluded that oxidants and... 

Polyacrylamide gel is the most commonly used type of support medium for gel electrophoresis, and polyacrylamide gel electrophoresis is simply known as PAGE. The gel is usually formed by polymerization of acrylamide and the cross-linking agent N, iV -methylene-bis-acrylamide (Bis) in the presence of ammonium persulfate (APS, initiator) and N, N, N, iV -tetramethyl-ethylenediamine (TEMED, accelerator). The total concentration of acrylamide... 

Grafting and networking may modify the mechanical, chemical, and functional properties of polymers and enhance their utilization for some purposes, such as for water treatment (Kumar and Verma, 2007 Mishra et al., 2003). Psyllium derivatives were prepared by grafting acrylonitrile onto psyllium molecules using a ceric ammonium nitrate and nitric acid system (Mishra et al., 2003). The resulted grafted psyllium samples were not soluble in commonly used solvents or their combinations. In 2007, methacrylic acid derivatives of psyllium were prepared using ammonium persulfate as initiator and cross-linked using N,N-methylenebisacryla-mide as the crosslinker (Kumar and Verma, 2007). The modified psyllium... 

In this study, mechanical properties of emulsion copolymers of viityl acetate and butyl aciylate, which consisted of a nonionic emulsifier (30 mol ethoxylated nottyl-phenol), an oligomeric stabilizator, and ammonium persulfate or potassium persulfate as initiators by changing monomer ratios from 90 10 to 10 90 for VAc BuA, were determined by differential scanning calorimeter. 

Polymerization of butyl acrylate was also studied by us in ethyl acetate/water two phase systems (3) using potassium persulfate/quaternary ammonium salts as the initiator system. Under these conditions (a minimum amount of water was used to dissolve the persulfate), it was found that symmetrical quat salts were more efficient than surfactant type quat salts. Also, the more lipophilic quat salts were more efficient. These results prompted us to propose formation of an organic-soluble quaternary ammonium persulfate via typical phase transfer processes. 

Until recently, the most detailed kinetic investigations of phase transfer free radical polymerizations were those of Jayakrishnan and Shah (11, 12). Both of these studies have been conducted in two phase aqueous/organic solvent mixtures with either potassium or ammonium persulfate as the initiator, and have corroborated our earlier conclusions (2, 3)... 

Aqueous PolyNIPAAM Homopolymer (PolyNIPAAM). To 20 mg NIPAAM dissolved in phosphate buffered saline, 2.3 mg of ammonium persulfate and 9.3 mg of N,N,N, N -tetramethylethylenediamine (TEMED) was added to initiate the free radical polymerization. The mixture was then incubated for 3 hours at room temperature. The polyNIPAAM was isolated by precipitation in 14.3%, by volume, saturated (NH4)2S04 After removal of residual (NH4)zS04 by ion exchange chromatography (Bio-Rad AG501-X8D), polyNIPAAM was stored as the lyophilized solid. 

Polymerizations Where possible, polymers and copolymers were prepared in normal saline buffered with 10 mM sodium phosphate (PBS), pH 7.4, by room temperature initiation of 1% monomer solutions using 40 mM TEMED (HCl) and 5 mM ammonium persulfate. However, due to poor solubility, 0.2% solutions of NTBAAM and proporationately lower initiator concentrations were used. 

The initiators used in emulsion polymerization are water-soluble initiators such as potassium or ammonium persulfate, hydrogen peroxide, and 2,2 -azobis(2-amidinopropane) dihydrochloride. Partially water-soluble peroxides such a succinic acid peroxide and f-butyl hydroperoxide and azo compounds such as 4,4 -azobis(4-cyanopentanoic acid) have also been used. Redox systems such as persulfate with ferrous ion (Eq. 3-38a) are commonly used. Redox systems are advantageous in yielding desirable initiation rates at temperatures below 50°C. Other useful redox systems include cumyl hydroperoxide or hydrogen peroxide with ferrous, sulfite, or bisulfite ion. 

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