Polymeric Thickening Agents

Xanthan gum (Fig. 5.3) exhibits high viscosity at low concentrations and is used as a thickener and suspending agent in food relishes, where acid stability and high 

Carboxymethylcellulose (Fig. 5.5), as a cellulose-modifled derivative, is most widely used in the food industry for noncaloric thickening and as a bodying agent in dietetic foods, and as a bulking agent with nutritional value. Propylene glycol alginate is used as a thickener for low-pH syrups. 

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Polymeric thickening agents used in foods typically are well soluble polysaccharides, with an excluded volume parameter [j clearly above zero. This implies that especially the dilute and semidilute regimes are often of importance. Viscosity of very dilute solutions has been discussed in Sections 6.2.2 and 6.3.2. For higher concentrations, the reduced viscosity (j sp/c) is higher, as is true for any system (see Figure 5.5), but for polymer solutions the viscosity increases far stronger with concentration as soon as the chain overlap concentration is reached. 

Many other acrylic, allylic and vinyl monomers are commercially available (see (10-16)) and appear frequently in the patent literature on polymeric thickening agents. In the anionic group of monomers are materials such as... 

Synthetic lubricants are made with neopentyl glycol in the base-stock polyester (24). Excellent thermal stabiHty and viscosity control are imparted to special high performance aviation lubricants by the inclusion of polyester thickening agents made from neopentyl glycol (25,26) (see LUBRICATION AND lubricants). Neopentyl glycol is also used to manufacture polymeric plasticizers that exhibit the improved thermal, hydrolytic, and uv stabiHty necessary for use in some exterior appHcations (27). 

Several systems may be used such as polymeric thickeners, fine particulate solids such as bentonite clays and oxides or combinations of the latter with polymers (1). The nature and level of the gelling agent required to prevent appreciable settling of particles and formation of hard "cakes" or clays depends on the density difference between disperse phase and medium, volume fraction of the disperse phase and interaction of the antisettling system with particles of the pesticide. 

Cellulose ethers, more particularly methyl cellulose (MQ, methylhydroxypro-pyl cellulose (MHPC) and hydroxypropyl cellulose (HPC) are used as protective colloids also called primary suspending agents in suspension polymerization for the manufacturing of S-PVC. Their role is maintaining the particle size of the resin. Hydroxyethyl cellulose (HEC) is preferred for manufacturing of vinyl acetate emulsion polymers and as a thickening agent in dispersimi paints. 

U.S. 5169552 (1992) [64] Wise (Procter Gamble) Polymeric thickener stabilizing agent buffering agent Improved bleach stability improved rheology shear thinning... 

Suspend without crystalline suspending agents or hydrophilic polymeric thickeners have good, nonslimy feel... 

The major emphasis in this chapter is on the first three items—the chemical and/or binding interactions of polymers to hair the chemical nature of hairsprays, setting products, and mousses and the in situ polymerization reactions in hair. Although the rheological properties of polymer solutions are especially important to formula viscosity and to the sensory perceptions of cosmetics, they will not be emphasized here. It suffices to say that cellu-losic ethers [8, 9] are probably the most important thickening agents in hair products, and ethoxylated esters and carboxy vinyl polymers are also important. 

Mackay and coworkers [33,34] and Moss and coworkers [35] showed that reactions of nucleophiles with phosphorus(V) esters, which are models for nerve agents, can be carried out effectively in microemulsions. The active agents often contain polymeric thickeners, and the solubilizing power of microemulsions is of crucial importance. Typically cationic surfactants are used with alcohols or alMpyrollidinones as cosurfactants. lodosobenzoate ions (2) are nucleophilic turnover catalysts toward fluorophosphonate nerve agents and phosphate esters, and Moss and coworkers used amphiphilic iodosobenzoate ions extensively in this work [36] (see Scheme 2). 

The production of polyvinyl acetate and alcohol was carried out in the early days not only in Germany but also in the United States, France, and United Kingdom. The first practical use of PVA in a large quantity was for warp-sizing of rayon and other synthetic fibers. In emulsion polymerization, it was used as an emulsifier or a stabihzer and also as a thickening agent for aqueous dispersion. All these uses have been continued and expanded. 

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