Carbopol solutions

Tang, C., et al. 2005. New superporous hydrogels composites based on aqueous Carbopol solution (SPHCcs) synthesis, characterization and in vitro bioadhesive force studies. Eur Polym J 41 557. 

Perez and Sandall (1974) studied the absorption of carbon dioxide in aqueous carbopol solution. The rheological behavior of the solution was described by the power law model with flow behavior indices varying from 0.91 to 0.59. For an agitated vessel with a turbine impeller, the mass-transfer coefficient across the unbroken interface was correlated as... 

There are a number of research studies, which have dealt with heat transfer in stirred tanks with non-Newtonian fluids. These were exclusively pseudoplastic liquids, whose viscosity obeys the power law (aqueous CMC, PAA and Carbopol solutions). 

The yield stress of viscoplastic fluids may be estimated by observing the motion/no motion of a sphere. For example, the yield stress for carbopol solutions was evaluated in [182]. 

FIGURE 10.17 Laminar heat transfer of Carbopol solutions in a 2 1 rectangular duct with upper wall heated [71]. 

An exception to the generally observed drag reduction in turbulent channel flow of aqueous polymer solutions occurs in the case of aqueous solutions of polyacrylic acid (Carbopol, from B.F. Goodrich Co.). Rheological measurements taken on an oscillatory viscometer clearly demonstrate that such solutions are viscoelastic. This is also supported by the laminar flow behavior shown in Fig. 10.20. Nevertheless, the pressure drop and heat transfer behavior of neutralized aqueous Carbopol solutions in turbulent pipe flow reveals little reduction in either of these quantities. Rather, these solutions behave like clay slurries and they have been often identified as purely viscous nonnewtonian fluids. The measured dimensionless friction factors for the turbulent channel flow of aqueous Carbopol solutions are in agreement with the values found for clay slurries and may be correlated by Eq. 10.65 or 10.66. The turbulent flow heat transfer behavior of Carbopol solutions is also found to be in good agreement with the results found for clay slurries and may be calculated from Eq. 10.67 or 10.68. 

The following flow rate - pressure drop data for a 0.2% aqueous carbopol solution (density 1000 kg/m ) have been reported for two capiUary tubes and three pipes of different diameters. (Data from D.W. Dodge, Ph D Thesis, University of Delaware, Newark, 1958). 

Figure 3.10 Turbulent flow behaviour of 0.2% carbopol solution (example 3.8)...

The resulting mean value of A is 2.78. Therefore, for this carbopol solution in turbulent flow, the wall shear stress is given as ... 

Figure 5.3 Size of sheared cavity around a sphere moving in a viscoplastic (aqueous carbopol) solution...

Only a very limited range of measiuements of physical properties has been made, and for dilute and moderately concentrated aqueous solutions of commonly used polymers including carboxymethyl cellulose, polyethylene oxide, carbopol, polyacrylamide, density, specific heat, thermal conductivity, coefficient of thermal expansion and surface tension differ from the values for water by no more than 5-10% [Porter, 1971 Cho and Hartnett, 1982 Irvine, Jr. et al., 1987]. Thermal conductivity might be expected to be shear rate dependent, because both apparent viscosity and thermal conductivity are dependent on structure. Although limited measmements [Loulou et al., 1992] on carbopol solutions confirm this, the effect is small. For engineering design calculations, there will be little error in assuming that all the above physical properties of aqueous polymer solutions, except apparent viscosity, are eqnal to the values for water. 

The thermo-physical properties including the effective viscosity are evaluated at the wall conditions of shear rate and temperature. For a power-law fluid therefore the effective viscosity is evaluated at the shear rate of (3n -I- l)/4n (8V/Z)). However, Oliver and Jenson [1964] foimd that equation (6.37) imderpredicted their results on heat transfer to carbopol solutions in 37 mm diameter tubes and that there was no effect of the (L/D) ratio. They correlated their results as (0.24 [Pg.273]

The coefficient of thermal expansion of the carbopol solution is assumed to be same as that for water, and the mean value in this temperature range is 0.000302 R-P Substituting values ... 

For a steam jacketed tank (360 mm in diameter) fitted with baffles, Hage-dorn and Salamone [1967] measmed the rates of heat transfer to water, glycerol and aqueous carbopol solutions over wide ranges of conditions (0.36 < n < 1 35 < Re < 6.8 x 10 Pr < 2.4 x 10 ). They measured temperatures at various locations in the vessel and suggested the following general form of heat transfer correlation ... 

The following rheological data have been reported for a 0.6% (by weight) carbopol solution in a 1.5% (by weight) NaOH aqueous solution at 292 K. 

The following shear stress-shear rate data are available for an aqueous carbopol solution at 293 K. 

A carbopol solution p = lOOOkg/m ), with Bingham plastic rheology (Tq = 8Pa and plastic viscosity of 50 m Pa-s), is flowing through a 25 mm diameter pipeline. Estimate the pressure drop per metre of pipe when the mean velocity is 1 m/s. Also, estimate the radius of the unsheared plug in the core region. 

Measurements are made of the yield stress of two carbopol solutions (density 1000 kg/m ) and of a 52.9% (by weight) silica-in-water suspension (density 1491 kg/m ) by observing their behaviour in an inclined tray which can be tilted to the horizontal. The values of the angle of inclination to the horizontal, 0, at which flow commences for a range of liquid depths, H, are given below. Determine the value of yield stress for each of these liquids. 

Viscometric measurements suggest that an aqueous carbopol solution behaves as a Bingham plastic fluid with yield stress of 1.96 Pa and plastic viscosity 3.80 Pa s. The liquid flows down a plate inclined at an angle 6 to the horizontal. Derive an expression for the volumetric flow rate per unit width of the plate as a function of the system variables. Then, show that the following experimental results for 0 = 5° are consistent with the theoretical predictions. 

Figure 14 Viscosity/shear-rate curves for 0.35% aqueous Carbopol solution.

Carbopol. Carbopol is provided as powder in a manner similar to CMC. It can be obtained in a large number of grades, some of which will produce yield stress fluids. The rheology of most Carbopol solutions is very sensitive to pH. 

Kumar, S., Himmelstein, K.J. Modification of in situ geUing behavior of carbopol solutions by hydroxypropyl methylcellulose. J. Pharm. Sd. 84(3), 344-348 (1995)... 

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