Polymeric Gelling Agents

Mixtures of hydrocoUoidal gelling agents in an aqueous medium have also been employed as water-soluble or water-dispersible additives to provide gels having solids-suspending properties. Such mixtures include a mixture of hydroxypropyl-cellulose and poly(l-alkene-maleic anhydride) as poly(isobutylene-co-maleic anhydride), and a blend of hydroxypropylcellulose and poly(alkyl vinyl ether-co-maleic anhydride) as poly(methyl vinyl ether-co-maleic anhydride) [91]. 

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Acylic Acid-Based Polymeric Gelling Agents... 

Dispersion of polymeric viscosifiers is often difficult because the initial contact of the untreated polymer with water results in very rapid hydration of the outer layer of particles which creates a sticky, rubbery exterior layer that prevents the interior particles from contacting water. The net effect is formation of what are referred to as nfish eyes" or "gel balls." These hamper efficiency by lowering the viscosity achieved per pound of gelling agent and by creating insoluble particles that can restrict flow both into the formation and back out of it. The normal remedy for this behavior... 

Adipic acid can also polymerize with alcohols such as ethylene glycol to form polyesters, which can combine with isocyanates to form polyurethanes. Smaller esters of adipic acid produced with alcohols in the C-8 to C-10 range are called adipates. These are used as softeners in plastic (such as polyvinyl chloride) and as synthetic grease base oils. Adipic acid is also used in the food industry. Food grade adipic acid is prepared synthetically or extracted from beet juice as a natural source. It is used as a gelling agent, as an acidulant to provide tartness, and as a preservative. 

Large volumes of soap are used in industrial applications as gelling agents lor kerosene, paint driers, and as surfactants in emulsion polymerization. See also Soaps. Concern over water eutrophication resulted in a ban of phosphorus in laundry detergents. Phosphates have been effectively replaced by combinations of zeolite, citrate, and polymers, coupled with rebalanced synthetic active systems. Soap itself is generally present only as a minor component of surfactants. 

We have found that mixing polyacrylamide and starch expands the versatility of both. In our experience, many enzymes that are not well resolved on starch or acrylamide alone are well-resolved on a mixture of the two. The five acrylamide/starch concentrations (weight/volume) we use most often are (1) 12% starch, (2) 7% acrylamide, (3) 9% acrylamide, (4) 7% acrylamide with 2% starch, and (5) 6% acrylamide with 4% starch. For gels containing acrylamide, the total amount of gelling agent is prepared as 95% acrylamide and 5% iV.iV -methylenebisacrylamide. Gel polymerization catalysts, ammonium persulfate (APS) and N,N,N, N -tetxa.-methylethylenediamine (TEMED), are 0.1% (w/v) and 0.2% (v/v) of the total volume of the gel buffer, respectively. 

Straight-chain alkyl carboxylic acids derived from petroleum that also have a terminal cyclohexyl or cyclopentyl group are known as naphthenic acids. They form complexes, presumably polymeric, with many transition metals, and these compounds are freely soluble in petroleum. Copper naphthenates are used as fungicides, aluminum naphthenate was used as a gelling agent in napalm, and cobalt naphthenates are used in paints. 

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. 

All samples were prepared by sol-gel synthesis in alkali-free medium via a polymeric gel route involving alkoxide hydrolysis and condensation, catalysed by base or acid. Similar reactant mixtures were used in all preparations and only the type of gelling agent was changed. 

Chemical gelling agents snch as glutaraldehyde have been widely used to produce hydrogel network of various synthetic and natnral polymers. The mechanism mainly involved in this technique is introduction of new molecnles between the polymeric chains to produce cross-linked chains. One snch example is hydrogel prepared by cross-linking of corn starch and polyvinyl alcohol using... 

A breakthrough in absorbent technology occurred in the 1960s with the advent of polymeric aqueous gelling agents, now popularly known as absorbent polymers or superabsorbents. These synthetic and modified natural polymers absorb many times their own weight of fluids and allow the fabrication of smaller yet more absorbent... 

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