Dextran viscosity data

The dextran produced by Betacoccua arabinosacemis (Birmingham) has also been examined by means of intrinsic-viscosity data. These data in-... 

The viscosities of both top and bottom phases formed in the MD systems were measured and found to be independent of shear rate (data not shown). Density and viscosity data are provided for the MD/PEG and dextran /PEG systems in Table 1. 

Dextran is perhaps one of the most extensively investigated polysaccharides, yet it has not achieved significant commercial success. It dissolves in cold water to produce viscous solutions, but the viscosity is low in comparison to the viscosity of many other polysaccharides used industrially. Viscosity data for a high molecular weight (5 to 40 x 10 Daltons) dextran and xanthan gum are shown in Table VII. 

Table 5 and Table 6 give some representative viscosity data for PAMAA and D-g-AM respectively in 1.5% NaCl solution after allowing for viscosity stability. The last column in the table displays the ratio of the intrinsic viscosity in deionized water, [ti]H20, and in 1.5% NaCl solution, [ri]NaCl. The ratio for PAMAA is a function of copolymer composition and structure and shows a maximum at about 50 mole % acrylamide we observe here an almost 50-fold decrease in [t]] for a 1.5% NaCl solution, whereas [r ] for homo-PAM is relatively insensitive to salt effects. The intrinsic viscosity for D-g-AM in salt solution shows no significant change from the intrinsic viscosity in water. The ratio [r ]H20/[r ]NaCl is comparable to that of dextran. 

Table 6. Viscosity Data for Poly(dextran-g-acrylamide) Samples in 1.5% NaCl Solution at 30 C ...

Honey density (at 20 °C) depends on the water content and may range from 1.4404 (14% water) to 1.3550 (21% water). Honey is hygroscopic and hence is kept in airtight containers. Viscosity data at various temperatures are given in Table 19.10. Most honeys behave like Newtonian fluids. Some, however, such as alfalfa honey, show thixotropic properties which are traceable to the presence of proteins, or dilating properties (as with op-untia cactus honey) due to the presence of trace amounts of dextran. 

The negative of the slope of the lines are shown plotted against the measured intrinsic viscosity of the polymers in Figure 3. The previously described coacervatlon model (8) predicts that the slope of this line should be unity. A line with this slope accurately represents the data, as expected. These results indicate that polyacrylamide has no attractive interaction with the mlcroemulslon particles (or with its components) and the interaction is a repulsive, excluded volume one. This leads to the conclusion that polyacrylamide is similar to the other nonionic water soluble polymers, PEO, PVP and dextran in its behavior toward water external mlcroemulslons, possibly by a "volume restriction" mechanlsm(15). 

Figure 5 shows the viscosity ratio of the Dextran-surfactant solution, ipatio " (dextran + surfactant)/ (dextran) (surfactant) > solutions containing SDBS and EHD. The data show that no binding occurs in case of both anionic SDBS and cationic EHD with nonionic dextran polymer. The absence of any surfactant binding is also confirmed by surface tension measurements (Figure 6) which show that the surface tensions of SDBS and SDS solutions in the absence of and in the presence of dextran are identical. 

Fig. 6 Radius of the equivalent hydrodynamic sphere (Stokes radius) for dextran and poly(ethylene oxide) in water. Calculated from the collected data of viscosity and diffusivity. The scales for two lines are displaced from each other for clarity, (Reproduced from ref. 32 with permission.)...

Figure 12.5 Low-shear viscosity of (a) (O) aqueous mesquite gum and ( ) gum arabic, based on data from Goycoolea, et a/.(21), (b)(0 ) 334, (A) 506, and (Q) 2660 kDa dextrans in water, based on data from loan, et al. 22,23), (c) 110 kDa polyvinylmethylether in toluene, using results of Martin(24), and (d) 215 kDa and 1.1 MDa polystyrene in dimethylformamide, based on measurements from Onyenemezu, et al.(25).

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