Emulsion synergism

The widespread applicability of di-O-methylisosorbide as a medium for chemical reactions or as a solvent for pharmaceutical formulations is well documented. In some cases, an additive synergism of the solvent and the solute was observed. Some typical examples mentioned include that it acts as a solvent for muscle-relaxant drugs, which are otherwise difficultly soluble,226 and is used for topical and other types of pharmaceutical formulations,227,228 transdermal controlled-release films229 and tapes,230 anthelmintic solutions,231 antimycotic emulsions,232 and for the treatment of skin disorders, such as eczema.233... 

Work carried out by Dove and Schroeder (1955) compared the use of oil- or water-based emulsion of 0.2% pyreihrins synergized by 2% PBO. The latter w ere found to be excellent since the emulsions broke on the surface, leaving an insecticidal deposit of equivalent performance to powder formulations, whereas... 

Wettable powder formulations of pyrethrins synergized with PRO were found to be longer-lasting for surface sprays against Indian meal moth, Plodia stuer-puncteila (Hubner), than water-diluted emulsions (Kanlack and Laudani, 1957. This is because of absorption of the active material into surface substrates when emulsion concentrates are used, whereas wettable powders leave a residual surface deposit, even if the water penetrates the surface,... 

Head louse infestations periodically cause disruptions at schools aii over the world. The treatment with pyrethrins and PBO is relatively cheap, and effective. The most common formulations contain either 0.15% or 0,3% pyrethrins synergized with 3.0% PBO formulated into non foaming shampoos (water- based pm-sized emulsions) that are applied directly to the affected area and repeated after i week to kill any newly hatched lice. The pediculicidal and ovicidal efficacy of synergized pyrethrins arc enhanced in shampoo formulations as a result of the surface-tension-lowering action of the formulation and are preferable to direct applications of lotions. 

The highly hydrophobic alkyd resin can serve as both reactant and coemulsifier (hydrophobe) in the mini-emulsion polymerization of alkyl (meth)acrylates [80, 110]. The strong synergism in the minidroplet nucleation was observed when highly hydrophobic unsaturated alkyd resin was used as the hydrophobe (>20 wt %). This feature is very different from the conventional coemulsifiers, such as long-chain alkanes and alcohols, that are effective around at 2 to 4%. 

The synergisms of mixtures of anionic-cationic surfactant systems can be used to form middle-phase micro emulsions without adding short-chain alcohols [109, 110]. The surfactants studied were sodium dihexyl sulphosuccinate and benzethonium chloride. The amount of sodium chloride required for the middle-phase microemulsion decreased dramatically as an equimolar anionic-cationic surfactant mixture was approached. Under optimum middle-phase microemulsion conditions, mixed anionic-cationic surfactant systems solubilised more oil than the anionic surfactant alone. Upadhyaya et al. [109] proposed a model for the interaction of branched-tail surfactants (Fig. 8.16). According to this model the anionic-cationic pair allows oil to penetrate between surfactant tails and increases the oil solubilisation capacity of the surfactant aggregate. Detergency studies were conducted to test the capacity of these mixed surfactant systems to remove oil from... 

Braun DB, Ciullo PA. Enhanced stabilization of topical emulsions through interactive synergism of cross-linked acrylic polymers and inorganic clays. 16th IFSCC Int Cong Preprints. New York Society Cosmetic Chemists, 1990 272-282. 

Polymerizetble in emulsion, solution, and bulk/suspenslon systems. Functions in all free radical polymerizations. AZO initiators are preferred. May be incorporated at conventional levels in the total polymer, added as a masterbatch when polymerized at a high concentration, or grafted into polymers. Masterbatches may be used for dry rubber or latex compounding. Synergizes with secondary antioxidants. When polymer bound, it is non-volatile, non-extractable, non-migratory, and non-staining. 

The average droplet size measured as a function of time indicated that neither Pluronic F-68 nor the fluorinated surfactants 1, 2, or 3 alone can produce a stable perfluorodecalin emulsion. The synergism between the two surfactants, Pluronic F-68 and a fluorinated surfactant, is essential for achieving storage stability. 

A single surfactant may satisfy all three roles, or there may be a requirement for multiple surfactants. The optimum choice of surfactant for one role may produce undesirable performance in other roles, and there may be positive or negative synergism exhibited when multiple surfactants are used. As with many other aspects of emulsion polymerization, a compromise is often required in the choice of surfactant. 

On a molecular level, the choice of surfactant for a given application must also take into consideration the type of emulsion desired and the nature of the oil phase. As a general rule, water-soluble surfactants yield OfW systems while oil-soluble materials preferentially produce W/0 emulsions. Because of the role of the interfacial layer in emulsion stabilization, a mixture of surfactants with widely differing solubility properties will often be found to produce emulsions with better stability than will ones with equivalent concentrations of either material alone. Looking for synergism in mixed surfactant systems can be a very valuable rule of thumb in the absence of more specific guidance. Finally, it is usually safe to say that the more polar the oil phase, the more polar will be the surfactant required to provide... 

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