Viscosity solutions

Measurement of the time.t, to pass the meniscus between the two marks and compare to the viscosity of the solvent. 

At the 0-temperature, the excluded volume effect is avoided (a = 1.0, see Sect. 1.3.). Making some solvent to rotate with the molecule leads to the equivalent sphere model. In this case one assumes that a certain inner solid sphere of solvent is 

For most polymers there is a definite relationship between molecular weight and solution viscosity. The viscosity method of molecular-weight determination 

However, the required information is the difference in the elution times of the solution and the pure solvent relative to the elution time of the pure solvent. Therefore, the elution time of the pure solvent, tg, is subtracted from the elution time of the solution, t. The thus obtained result is divided by tg. The resulting quantity is called the specific viscosity, which is a dimensionless quantity  

If the measurement is made in a capillary viscometer of specified dimensions and at low polymer concentration (so that the density of the solution is approximately the same as that of the solvent), the viscosities q and qo are represented to a good approximation by the elution times f and tg. It follows that  

If this value is divided by the concentration c of the polymer in solution, one obtains the reduced specific viscosity, v[ plc. 

Polymer solutions are never ideal since dissolved macromolecules influence each other even at very low concentration. On the other hand, a reliable correlation of solution viscosity and molecular weight is only possible if the dissolved macromolecules are not affected by mutual interactions they must be actually independent of each other. Therefore, the viscosity of polymer solutions shoifld be determined at infinite dilution. However, such measurements are impossible in practice. So one works at an as low as possible polymer concentration and extrapolates the obtained values to zero concentration. To do so, the elution time 

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The segmental friction factor introduced in the derivation of the Debye viscosity equation is an important quantity. It will continue to play a role in the discussion of entanglement effects in the theory of viscoelasticity in the next chapter, and again in Chap. 9 in connection with solution viscosity. Now that we have an idea of the magnitude of this parameter, let us examine the range of values it takes on. 

Both the intrinsic viscosity and GPC behavior of random coils are related to the radius of gyration as the appropriate size parameter. We shall see how the radius of gyration can be determined from solution viscosity data for these... 

Before turning to this, however, it is useful to introduce some additional vocabulary that is often employed in discussing solution viscosity. Equation (9.10) is a special case of the general function... 

Table 9.1 Summary of Names and Definitions of the Various Functions of 77, 77o, and C2 in Which Solution Viscosities are Frequently Discussed...

The concentric cylinder viscometer described in Sec. 2.3, as well as numerous other possible instruments, can also be used to measure solution viscosity. The apparatus shown in Fig. 9.6 and its variations are the most widely used for this purpose, however. One limitation of this method is the fact that the velocity gradient is not constant, but varies with r in this type of instrument, as noted in connection with Eq. (9.26). Since we are not considering shear-dependent viscosity in this chapter, we shall ignore this limitation. 

The number-average molecular weight of most commercially available acetal resins is between 20,000 and 90,000. Weight-average molecular weight may be estimated from solution viscosities. 

Solution Properties. Typically, if a polymer is soluble ia a solvent, it is soluble ia all proportions. As solvent evaporates from the solution, no phase separation or precipitation occurs. The solution viscosity iacreases continually until a coherent film is formed. The film is held together by molecular entanglements and secondary bonding forces. The solubiUty of the acrylate polymers is affected by the nature of the side group. Polymers that contain short side chaias are relatively polar and are soluble ia polar solvents such as ketones, esters, or ether alcohols. As the side chaia iacreases ia length the polymers are less polar and dissolve ia relatively nonpolar solvents, such as aromatic or aUphatic hydrocarbons. 

Polymer solution viscosity is dependent on the concentration of the solvent, the molecular weight of the polymer, the polymer composition, the solvent composition, and the temperature. More extensive information on the properties of polymer solutions may be found ia refereaces 9 and 54—56. 

AN, wt % Tensile strength, MPa Elongation, % Impact strength, J/m notch Heat distortion, temp., °C Solution viscosity, mPa-s (=cP)... 

Polyamines can also be made by reaction of ethylene dichloride with amines (18). Products of this type are sometimes formed as by-products in the manufacture of amines. A third type of polyamine is polyethyleneimine [9002-98-6] which can be made by several routes the most frequently used method is the polymeriza tion of azitidine [151 -56 ] (18,26). The process can be adjusted to vary the amount of branching (see Imines, cyclic). Polyamines are considerably lower in molecular weight compared to acrylamide polymers, and therefore their solution viscosities are much lower. They are sold commercially as viscous solutions containing 1—20% polymer, and also any by-product salts from the polymerization reaction. The charge on polyamines depends on the pH of the medium. They can be quaternized to make their charge independent of pH (18). 

Uses of gelatin are based on its combination of properties reversible gel-to-sol transition of aqueous solution viscosity of warm aqueous solutions abUity to act as a protective coUoid water permeabUity and insolubUity in cold water, but complete solubUity in hot water. It is also nutritious. These properties are utilized in the food, pharmaceutical, and photographic industries. In addition, gelatin forms strong, uniform, clear, moderately flexible coatings which readily sweU and absorb water and are ideal for the manufacture of photographic films and pharmaceutical capsules. 

The properties of a botanical gum are determined by its source, the climate, season of harvest, and extraction and purification procedures. Table 6 illustrates one of the important basic properties of all gums, ie, the relationship between concentration and solution viscosity. The considerable viscosity variation observed among gums from different sources determines, in part, their uses. 

Methacrylic acid polymer is iasoluble ia the monomer, which may result ia the plugging of transfer lines and vent systems. Polymers of the lower alkyl esters are often soluble ia the parent monomer and may be detected by an iacrease ia solution viscosity. Alternatively, dilution with a nonsolvent for the polymer such as methanol results ia the formation of haze and can be used as a diagnostic tool for determining presence of polymer. 

Solution Polymers. Methacryhc solution polymers are usually characterized by thek composition, soHds content, viscosity, molecular weight, glass-transition temperature, and solvent type. The compositions of methacryhc polymers are most readily determined by physicochemical methods such as spectroscopy, pyrolytic gas—Hquid chromatography, and refractive index measurements. The soHds content is determined by dilution followed by solvent evaporation to constant weight. Solution viscosities are most conveniendy determined with a Brookfield viscometer. Methods for estimating molecular weights by intrinsic viscosity are available (103). 

The substantial decrease of polyacrylamide solution viscosity in mildly saline waters can be uti1i2ed to increase injection rates. A quaternary ammonium salt polymer can be added to the polyacrylamide solution to function as a salt and reduce solution viscosity (144). If the cationic charge is in the polymer backbone and substantially shielded from the polyacrylamide by steric hindrance, formation of an insoluble interpolymer complex can be delayed long enough to complete polyacrylamide injection. Upon contacting formation surfaces, the quaternary ammonium salt polymer is adsorbed reducing... 

Foi chemical studies the chiomatogiaphic methods oi solution viscosities ate methods of piefeience, but for practical apphcations, melt flow is most... 

Fig. 2. Functional end groups and solution viscosity during polyester resin manufacture. Acid value is defined as the milligrams of KOH required to neutralize 1 g of polymer hydroxyl value is defined as the milligrams of acid equivalent required to neutralize 1 g of polymer. Solution viscosities are...

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