Polyacrylamide packing

In packed beds of particles possessing small pores, dilute aqueous solutions of hydroly2ed polyacrylamide will sometimes exhibit dilatant behavior iastead of the usual shear thinning behavior seen ia simple shear or Couette flow. In elongational flow, such as flow through porous sandstone, flow resistance can iacrease with flow rate due to iacreases ia elongational viscosity and normal stress differences. The iacrease ia normal stress differences with shear rate is typical of isotropic polymer solutions. Normal stress differences of anisotropic polymers, such as xanthan ia water, are shear rate iadependent (25,26). 

Polyacrylamide powders are typically shipped in moisture-resistant bags or fiber packs. Emulsion and solution polymers are sold in dmms, tote bins, tank tmcks, and tank cars. The transportation of dry and solution products is not regulated in the United States by the Department of Transportation, but emulsions require a DOT NA 1693 label. 

J. N. Kinkel, Optically active polyacrylamide/silica composites and related packings and their application to chiral separations in A practical approach to chiral separations by liquid chro-matogratphy, G. Subramanian, VCH, Weinheim (1994) Chapter 8. 

Polymerization in aqueous solution of acrylamide can also be fulfilled in thin layers (up to 20 mm) applied on a steel plate or a traveling steel band. Polymerization is initiated by persulfates, redox system, UV or y radiation. Polymerization proceeds in isothermal conditions as the heat of polymerization is dissipated in the environment and, additionally, absorbed by the steel carrier. Nonadhesion of the polymer to the carrier is ensured by the addition of glycerol to isopropyl alcohol or by precoating the steel band with a film based on fluor-containing polymers. This makes polymerization possible at a high concentration of the monomer (20-45%) and in a wider process temperature range. This film of polyacrylamide is removed from the band, crushed, dried, and packed. 

In the investigation reported herein, an attempt has been made to maximize peak separation and minimize peak broadening for aqueous GPC of polyacrylamides with CPG porous glass packings. 

Figure 2. Molecular weight calibration curves for nonionic polyacrylamide for a single column (4 ft X Vs in. i.d.) containing 2000 A CPG-10 (200/400 mesh) packing with aqueous salt solutions as mobile phase.

Figure 7. Molecular weight calibration curve for nonionic polyacrylamides for a 6-column combination (each 4 ft X in, Ld.) with 3000 A, 3000 A, 2000 A, 1000 A, 729 A, and 500 A CPG-10 (200/400 mesh) packing.

Polyacrylamide gel electrophoresis results suggest that p-LG undergoes a greater conformational loss as a fimction of extrusion temperature than a-LA, presumably due to intermolecular disulfide bond formation. Atomic force microscopy indicates that texturization results in a loss of secondary structure of aroimd 15%, total loss of globular structure at 78 °C, and conversion to a random coil at 100 °C (Qi and Onwulata, 2011). Moisture has a small effect on whey protein texturization, whereas temperature has the largest effect. Extrusion at or above 75 °C leads to a uniform densely packed polymeric product with no secondary structural elements (mostly a-helix) remaining (Qi and Onwulata, 2011). 

In the previously described electrophoretic methods, the capillary was filled with electrolytes only. Another mode of operation in capillary electrophoresis involves filling the capillary with gel or viscous polymer solutions. If desired, a column can be packed with particles and equipped with a frit.68 This mode of analysis has been favorably used for the size determination of biologically important polymers, such as DNA, proteins, and polysaccharides. The most frequently used polymers in capillary gel electrophoresis are cross-linked or linear polyacrylamide,69 cellulose derivatives,70-75 agarose,76 78 and polyethylene glycols. 

Cationic polyacrylamide may be used in the initial treatment stages to promote rapid polymer adsorption (201). Adjustment of the pH may allow deeper penetration of the fluids in an aluminate crosslinking system prior to gelation (202). A process involving injection of alternate slugs of stoichiometrically equivalent amounts of partially hydrolyzed polyacrylamide and Al O ) has been evaluated in the laboratory permeability of sana packs were reduced by more than 96% (203). Mixtures of Al(IIl) and Zr(IV) have also been evaluated as partially hydrolyzed polyacrylamide crosslinkers (204). 

The chromatographic procedure may be performed using (a) a column (about 85 cm x 10 mm) packed with polyacrylamide or cross-linked dextran for chromatography having a fractionation range for peptides with... 

The results from such experiments indicate that membrane ion current is very dependent on molecular packing with respect to the other membrane parameters of Table I. This factor must be considered in any new design for development of a sensing device to ensure that substantial molecular mobility may be incorporated Into stabilized membranes. Such a stabilized, e1ectrochemica 1 1y active membrane has been produced by lipid monolayer deposition onto hydrated polyacrylamide gel, demonstrating that device fabrication may be possIb1e. 

---