Polymer gel formation

On the space shuttle flights STS-57 and STS-63 Brown et al. studied polymer gel formation and produced superior gels for gas separation and for proprietary applications (36,37),... 

The formation of condensation structures is the main cause for the gelling of solutions of various natural and synthetic polymers. Gel formation may be accompanied by conformational changes of the polymer molecules, as is the case with gelatin and other biopolymers, or by various chemical interactions. Such is the acid-catalyzed synthesis of synthetic leather by the partial acetylation of polyvinyl alcohol with formaldehyde. Under supersaturation conditions, the fibers of the polyvinyl formal form in this system and develop into the network structure of synthetic leather. 

Guo et al. [70,71,73] recently attempted to hydrogenate NBR in emulsion form using Ru-PCy complexes. However, successful hydrogenation can only be obtained when the emulsion is dissolved in a ketone solvent (2-butanone). A variety of Ru-phosphine complexes have been studied. Crosslinking of the polymer could not be avoided during the reaction. The use of carboxylic acids or first row transition metal salts as additives minimized the gel formation. The reactions under these conditions require a very high catalyst concentration for a desirable rate of hydrogenation. 

Emulsion polymers cannot be fed neat. Always add emulsions to water (never water to emulsions) to avoid gel formation. Dilute emulsions to 1 to 2% in-use strength for batch processes. 

A derivatized hydroxyethylcellulose polymer gel exhibited excellent fluid-loss control over a wide range of conditions in most common completion fluids. This particular grated gel was compatible with the formation material and caused little or no damage to original permeability [1341]. Detailed measurements of fluid loss, injection, and regained permeability were taken to determine the polymer particulate s effectiveness in controlling fluid loss and to assess its ease of removal. Hydroxyethylcellulose can be etherified or esterified with long chain alcohols or esters. An ether bond is more stable in aqueous solution than is an ester bond [96]. 

The polymer solutions are pumpable as such, but in the presence of multivalent metal ions, gels are formed. The gel formation is caused by an inter-molecular crosslinking, in which the metal ion forms bonds to the polymer. 

Polymers of acrylic acid and methacrylic acid have been tested for their gel-formation ability [1396]. They are used with gel-forming additives similar to those described for polyacrylamides. Also, mixtures of latex with methacrylate-methacrylic acid copolymer as an additive have been described as plugging agents [1041]. 

The synergism of surfactant-polymer complex formation has been studied by gel permeation chromatography [114],... 

HIGH PURITY TRIMER NECESSARY - OTHERWISE GEL FORMATION HIGH POLYMER (MW-106)... 

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