Polyacrylamide-1-water

Fig. 4. Critical concentrations of polystyrene/toluene and polyacrylamide/water at 25 °C in relation to molar mass determined by viscometry and light scattering... 

Fig. 21. Recoverable strain as a function of shear stress for polystyrene/toluene solutions with different molar masses at 5 wt%. (+) polyacrylamide/water solutions, ( ) 2 wt%, (x) 2 wt% (with surfactant), (O) 4 wt% and polyethylene melts...

Eustace, D. J. Siano, D. B. Drake, E. N., "Polymer Compatibility and Interpolymer Association in the Poly(Acrylic Acid)-Polyacrylamide- Water Ternary System," J. Appl. Polym. Sci., 35, 707 (1988). 

GOM Gomes de Azevedo, R., Rebdo, L.P.N., Ramos, A.M., Szydlowski, J., DeSousa, H.C., and Klein, J., Phase behavior of (polyacrylamides + water) solutions Concentration, pressure and isotope effects. Fluid Phase Equil, 185, 189, 2001. 

HPLC using the reverse phase mode, has heen used to determine acrylamide mononer and related compounds, including methacrylonitrile in polyacrylamide. Water soluble compounds such as acrylamide and methacrylamide have sufficient lipophilic character that they can be retained and separated on HPLC reverse-phase columns using water as the eluent. By employing a low wavelength UV detector, these compounds can be measured with high sensitivity. The relative precision of the 95% confidence level for acrylamide is 7.5%. 

The frictional properties of the gel are appropriately determined by permeation experiments. However, only few studies on the dependence of the permeation on concentration have been made. Moreover, it appears that the permeation is very sensitive to the preparation procedure and thus to the structural inhomogeneities of the gel. One experiment was performed on polyacrylamide-water gel at concentrations between 5% and 35% (g/g). This study shows that the permeability factor is only controlled by the concentration, it is independent of the degree of crosslinking, and Kp decreases as g... 

This equation of motion was derived and tested experimentally for the first time by Tanaka et al. on polyacrylamide-water gels. From quasi-elastic light scattering and permeation and uniaxial compression experiments, they determined the order of magnitude of the three parameters D, pf, and M. They found that the ratio M/pf is close to the measeured D values. 

To check the predicted power law of the diffusion coefficient (Eq. (D-17)), experiments on polyacrylamide-water gels were carried out. It has been found that the exponent X0 lies between 0.65 and 0.75, and that these values are not too far firom the predicted value 0.75 . However, the system studied is polar and a polyelectrolyte behaviour due to partial hydrolysis of the amide group cannot be excluded. ... 

Fig. 11. CJiaracteristic timer of swelling of spherical polyacrylamide-water gels as a hinc-tion of the square of the final radius b. From Tanaka et al. ...

Solid Polymer. Completely dry polyacrylamide is a brittle white soHd. Commercially available dry polyacrylamide powders are typically dried under mild conditions and usually contain 5—15% water. The powders are hygroscopic, and generally become increasingly hygroscopic as the ionic character of the polymer increases. Cationic polymers are particularly hygroscopic. 

Polymers in Solution. Polyacrylamide is soluble in water at all concentrations, temperatures, and pH values. An extrapolated theta temperature in water is approximately —40° C (17). Insoluble gel fractions are sometimes obtained owing to cross-link formation between chains or to the formation of imide groups along the polymer chains (18). In very dilute solution, polyacrylamide exists as unassociated coils which can have an eUipsoidal or beanlike stmcture (19). Large aggregates of polymer chains have been observed in hydrolyzed polyacrylamides (20) and in copolymers containing a small amount of hydrophobic groups (21). 

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). 

The preparation of polyacrylamides and postpolymeri2ation reactions on polyacrylamides are usually conducted ia water. Reactions on the amide groups of polyacrylamides are often more compHcated than reactions of simple amides because of neighboring group effects. Reaction rates, for example, can differ considerably. 

Reaction with Chlorine. Polyacrylamide reacts with chlorine under acid conditions to form reasonably stable A/-chloroamides. The polymers are water soluble and can provide good wet strength and wet web strength in paper (60). 

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