Other ingredients in emulsion

The other ingredients in vinyl film are not totally free from guilt either. One might expect resins themselves to be impervious to fungus growth, yet films containing various resins differ widely in their susceptibility to attack. At least one factor involved is the residual soap or surfactant on the surface of emulsion poly (vinyl chloride) (PVC) resins. Undoubtedly there are many other causative factors as well. 

The most widely used hot melt adhesives are those based on ethyiene vinyl acetate (EVA). EVA is a very versatile resin and is typically compounded with waxes and tackifying resins, along with stabilizers, antioxidants, and other components if desired. The properties, including melting temperature, of the adhesive depend on the molecular weight of the base polymer and its vinyl acetate content, as well as on the other ingredients in the formulation. Typical VA content ranges from 5% for adhesives intended for nonpolar substrates to 30% for those to be used for more polar substrates. EVA adhesives are economical and have very low odor, taste, and toxicity characteristics. In addition to use in hot melts, they are often used in emulsion adhesives. 

Getting an emollient distributed evenly on your skin is not as easy as it may seem. Instead of just pouring oil over your body after a shower (this would leave your skin too oily), it would be better to use a mixture containing the emollient. Two kinds of mixtures are commonly used creams and lotions are made by mixing an oily component with water and other ingredients in the right proportions to form a stable mixture that can be more like a solid (a cream) (Figure 15.7) or more like a liquid (a lotion). Mixtures like these are called emulsions. Emulsions consist of two substances that would... 

Amine oxides have also found a role in emulsification. A prior publication makes note of the use of amine oxides as emulsifiers and lists many useful characteristics that make them attractive in cosmetic formulations [37]. They are reported to be extremely mild in skin and eye irritation tests and disclose a synergistic counter irritancy when blended with other ingredients. In addition, amine oxides are known to impart lubricity and emollience to skin surfaces in acidic emulsions [38]. 

Extended stability testing is a necessity for emulsion systems in metal containers because of the corrosion potential of water and some of the other ingredients. In most cases where a stable emulsion exists, there is less corrosion potential in a w/o system because the water is the internal phase. 

Emulsifiers are classified by the hydrophilic—lipophilic balance (HLB) system. This system indicates whether an emulsifier is more soluble in water or oil, and for which type of emulsion (water-in-oil or oil-in-water) it is best suited. Emulsifiers having alow HLB value are more oil soluble, and are better suited for water-in-oil appHcations such as margarine. Conversely, emulsifiers having a high HLB value are more water soluble, and function more effectively in oil-in-water emulsions such as ice cream (34). The use of this system is somewhat limited because the properties of emulsifiers are modified by the presence of other ingredients and different combinations of emulsifiers are needed to achieve a desired effect. The HLB values of some common emulsifiers are given (35). 

The reaction is considerably modified if the so-called emulsion polymerisation technique is used. In this process the reaction mixture contains about 5% soap and a water-soluble initiator system. The monomer, water, initiator, soap and other ingredients are stirred in the reaction vessel. The monomer forms into droplets which are emulsified by some of the soap molecules. Excess soap aggregates into micelles, of about 100 molecules, in which the polar ends of the soap molecules are turned outwards towards the water whilst the non-polar hydrocarbon ends are turned inwards (Figure 2.17). 

Surfactants are widely used industrially and perform a variety of functions. As processing aids they help to disperse fillers and other ingredients and to form and stabilize emulsions. They are key components in shampoos, detergents, polishes and cleaning products. In other... 

No systematic studies of the use of silicone surfactants as emulsifiers have yet been published. Silicone polyoxyalkylene copolymers with relatively high molecular weight and a high proportion of silicone are effective water-in-silicone oil emulsifiers and a recent study of these copolymers suggests that they stabilize emulsions by a solid-particle mechanism [68]. This type of silicone surfactant has been used to prepare transparent water-in-oil emulsions (often with an active ingredient in the internal phase) for use as deodorants or antiperspirants as well as cosmetics and other personal care products. Their use as drug delivery vehicles has also been claimed. These copolymers can also be used to prepare multiple emulsions not requiring a two-pot process. 

In general, these groups of cellulose ethers have been used for their innate adhesive properties and to provide thickening to adhesive formulations. They are used for plywood adhesives, industrial adhesives, wallpaper paste, library paste, and latex adhesives. For example, methylcellulose is used in some adhesives as an additive to control viscosity, especially in the heat-cure phenol-formaldehyde glues and other hot-pressing adhesives. Hydroxyethylcellulose is used as an ingredient in polyvinyl acetate emulsions, where it acts as a thickener and protective colloid. 

In industrial emulsion polymerizations, CTAs like mercaptan are often used to regulate the molecular weight of the polymer produced. In some cases, other ingredients that directly participate in the polymerization reaction are used to modify the properties of the polymer latex produced. In these cases, these... 

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