S/A emulsions

Gulf Canada Limited (20, 2T). The process developed by Gulf consists of a pumping system wfnch continuously delivers measured volumes of sulfur and asphalt to a mixing device which disperses the molten sulfur in the liquid asphalt. The composition of the emulsion is typically in the range 25-60 parts sulfur to 75-40 parts asphalt. The temperatures of the sulfur, asphalt and S/A emulsion are maintained in the ranges 121-154 C, 121-177 C, and 121-154 C, respectively. 

The optimal temperature range for manufacture of the emulsion is 130-170 C. These S/A emulsions are claimed to be particularly suitable as binders for pavement construction. 

Rennie, W. J., "Sulphur Asphalts The Pronk S/A Emulsion Binder System", SUDIC, New Uses for Sulphur, 1978, 3. 

Figure 6. Variation of viscosity with shear rate (T = 25° C). = 80-100 conventional asphalt (linear). = 20-80 S/A emulsion with 80-100 asphalt. = 40-50 asphalt (linear). = 30-70 S/A emulsion with 80-100 asphalt. = 20-30 blown asphalt (not linear).

Figure 9. Relaxation distribution function using the Roesler and Twyman method. = 80-100 shell asphalt. = 30-70 S/A emulsion.

A. S. Dunn, Emulsion Polymerization (I. Piirma, ed.) Academic Press, New York, Chapter 6, (1982). 

Lovell, P.A. El-Aasser, M.S., Eds. Emulsion Polymerization and Emulsion Polymers John Wiley Sons London, 1997. 

The early attempts at NMP of S in emulsion used TEMPO and related nitroxides and needed to be carried out at high temperatures (100-130 °C) necessitating a pressure reactor. Problems with colloidal stability and molecular weight control and limiting conversions were reported.215 217... 

The types of microorganisms found in various products are Pseudomonas species, including Pseudomonas aeruginosa, Salmonella, species, Staphylococcus aureus, and Escherichia coli. The USP and other pharmacopoeias recommend certain classes of products to be tested for specified microbial contaminants, e.g., natural plant, animal, and some mineral products for the absence of Salmonella species, suspensions for the absence of E. coli, and topically administered products for the absence of P. aeruginosa and S. aureus. Emulsions are especially susceptible to contamination by fungi and yeasts. Consumer use may also result in the introduction of microorganisms. For aqueous-based products, it is therefore mandatory to include a preservative in the formulation in order to provide further assurance that the product retains its pharmaceutically acceptable characteristics until it is used by the patient. 

Particle Size Distribution Determination. To consider the full PSD, a population balance or age distribution analysis on particles must be employed. Table II gives a summary of recent work concerning the determination of PSD s in emulsion systems, using both the "monodispersed" approximation and the population balance approach. More details can be found in the literature sources cited in the Table. 

Suspensions offer another dispersed platform for delivery of poorly water-soluble agents. As compared with solutions, suspensions afford higher loading. However, as with emulsions, the suspended particles must be stabilized with surfactants to prevent aggregation. A number of steroids have been available for years as suspensions for IM and intra-articular delivery. Examples include DEPO-MEDROL (Pfizer, Kalamazoo, Michigan, U.S.A.) Sterile Aqueous Suspension. The marketed product contains methylprednisolone acetate, a white, water-insoluble, crystalline... 

FIGURE 4. Spectral distribution of Herschel effect at 77K. Exposure, 2.8 x 106 ergs/cm to radiation specified on abscissa, o, Unsensitized AgBr emulsion, 0.2-pm grains A, same, except S-sensitized emulsion, AD/D0, fractional loss of developable density as result of long wavelength exposure. 

The combined (S + Au)-sensitization usually is applied during the manufacture of the emulsion, but sensitization can be achieved also by bathing a coated S-sensitized emulsion in an aurous thiocyanate solution before exposure (161). Reduction sensitization can be combined with (S + Au)-sensitization under some conditions. Collier (162) found that reduction sensitization either before or after (S + Au)-sensitization increased both sensitivity and fog in a l-ym octahedral grain silver bromide emulsion. The largest increase in sensitivity and lowest increase in fog were achieved when reduction sensitization was applied after the S+Au. Hydrogen hypersensitization likewide is effective (108) and can produce large increases in sensitivity for some emulsions. 

They arrived at a size of the order of 100 silver atoms for a bare metal nucleus, but only 10 atoms for a nucleus embedded in gelatin. Moisar and associates (205) estimated the minimum size as four silver atoms. Ronde (206) revised their calculations and obtained 10 for an unsensitized silver bromide emulsion and six for a S-sensitized emulsion. The validity of the Gibbs-Thomson equation for such small sizes, however, is questionable. 

The seed latex was prepared by emulsion polymerization at 50°C using distilled water, 4 dnrr SDS, 50g PPS, 5g and distilled styrene, 440g. Two batches were prepared, one in U.S.A. and one in Japan with same recipe. 

The Eastern Forest Products Laboratory, Ottawa, found that ammoniacal zinc oxide is an inhibitor to fungi in pine lumber (16,33). Sanford Products Corp. is offering 2- hiocyanomethyi(thic) benzothiazole for prevention of sapstain and mould in Canada and U.S.A., and tributyl tinoxide emulsion is marketed in Japan. 

Gee, R.P. (1986) Method of preparing silicone emulsions having small particle size. U.S. 4620878. (Dow Corning Corp. U.S.A). 

Monteiro, M.J., Brussels, R. and Wilkinson, T.S. (2001) Emulsion polymerization of methyl methacrylate in the presence of novel addition-fragmentation chain-transfer reactive surfactant (transurf). /. Polym. Sci., A 39,2813-20. 

American scientists had learned a little about Buna and Buna-S that the Germans had developed. Building on this rudimentary knowledge, a procedure was worked out to produce GR-S by emulsion polymerization (see Chapter 5). 

Fig. 8. W/O emulsions in pure Span 80 (sorbitan monooleate) a premixed emulsion, b emulsion sheared at 50 s c emulsion sheared at 1000 s 1, d emulsion sheared at 3000 s. Note that for images a and b, the bars represent 122 pm whereas for images c and d they represent 12.2 pm...

Davis, S. S. (1982), Emulsions systems for the delivery of drugs by the parenteral route, in Bundgaard, H., Bagger Hansen, A., and Kofod, H., Eds., Optimization of Drug Delivery, Munksgaard, Copenhagen, pp. 333-346. 

Muchtar, S., and Benita, S. (1994), Emulsions as drug carriers for ophthalmic use, Coll. Surf. A Physicochem. Eng. Aspects, 91,181-190. 

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