Sizing Specific viscosity

For parenteral products specific consideration needs to be included for tonicity adjustment, emulsion globule size, ease of resuspension and sedimentation rate, particle size and particle size distribution, viscosity and syringeability, and crystal form changes. Full consideration should be included of the proposed instructions for dilution or reconstitution of products and of compatibility with the proposed solvents or diluents. This should include a demonstration that the proposed storage temperature and extremes of concentration are suitable. 

Particle size specifications for the active component resuspendability, viscosity, sedimentations rates, caking, and syringeability of suspensions... 

Another very useful approach to molar mass information of complex polymers is the coupling of SEC to a viscosity detector [55-60]. The viscosity of a polymer solution is closely related to the molar mass (and architecture) of the polymer molecules. The product of polymer intrinsic viscosity [r ] times molar mass is proportional to the size of the polymer molecule (the hydrodynamic volume). Viscosity measurements in SEC can be performed by measuring the pressure drop AP across a capillary, which is proportional to the viscosity r of the flowing liquid (the viscosity of the pure mobile phase is denoted as r 0). The relevant parameter [r ] is defined as the limiting value of the ratio of specific viscosity (qsp= (n-noVflo) and concentration c for c—> 0 ... 

It seems probable that, as with desoxyribosenucleic acid, the size of the particles of ribosenucleic acid depends upon the treatment to which the acid has been subjected, the size being smaller when less mild methods of isolation are applied. Bawden and Pirie had pointed out that the size of the tobacco mosaic virus ribosenucleic acid particles is larger than that of the particles of yeast ribosenucleic acid as usually prepared. Loring has now found that purified, commercial yeast ribosenucleic acid solutions have about the same specific viscosity as have solutions of the alkali-treated ribosenucleic acid of tobacco mosaic virus hence, their molecular sizes are probably of the same order (about 15,000). 

Particle characteristics include the particle size distribution and average size, specific gravities and bulk density, spho icity and heat capacity. Important gas characteristics include gas density, viscosity and heat capacity, which are all temperature dependent. Moreover, the composition of the gas mixture is also an important parameter in reactor design. The reaction kinetics and thermodynamics can be defined by literature data or by experimental work. 

There are several dilute solution viscosity quantities used in the determination of the intrinsic viscosity. The size of macromolecules in solution is associated with an increase in viscosity of the solvent brought about by the presence of these molecules. Relative viscosity is a dimensionless quantity representing a solution/solvent viscosity ratio, r], = 7j/i o. where 17 and 170 are the solution and solvent viscosities, respectively. The specific viscosity yj p = 77 1 is the fractional increase in vis-... 

Not enough is known about the mechanism of action of these macromolecules. They commonly appear to act by interfering with water movement in plant tissues due to mechanical plugging of the vessels which leads to wilt symptoms. The phenomenon could well be related to molecule size and viscosity rather than to their structure [84], though some results on host specificity [89] and on viscosity interference [90] would suggest a possible different behaviour in some cases. 

The correlation length f becomes smaller than electrostatic blob size Dg at concentrations higher than ct- Electrostatic interactions are not important in polyelectrolyte solutions with concentration c above Cb and specific viscosity is expected to have concentration dependence similar to that in solutions of entangled neutral polymers, This quasi-neutral... 

Bell evaluated the thickening efficiency of PTFE powders with surface areas from 2.3 to 20 m /g and found the required amount of PTFE to attain their goal viscosity was reduced from 34.3 to 20.0%. The emphasis of Maccone et al. was the development of a PTFE with a primary particle size of 50 nm and a surface area of 30 m /g. About 50% less of this PTFE was required compared to a control (230 nm particle size and 8 m /g) to produce grease with a specific viscosity. 

The viscosity of a polymer solution is related to the size and extension of the polymer molecule in that particular solution larger molecular species are generally associated with higher solution viscosities. In this section, the issue of the molecular size of the polymer is discussed mainly in the light of viscosity-related properties of the polymer solution. Relationships are developed that apply to both random coil molecules, such as HPAM, and more rigid macromolecules like xanthan. A number of other quantities are related to viscosity these include the relative viscosity, specific viscosity, reduced viscosity and inherent viscosity, which are defined in Table 3.1. (Billmeyer, 1971 Rodriguez, 1983). Clearly, all of these quantities are related to the polymer concentration in solution, and a more fundamental quantity which will be defined is the intrinsic viscosity, [ ]. The intrinsic viscosity is the limit of the reduced viscosity or inherent viscosity as the solution concentration of polymer tends to zero as shown below. 

The viscosity of dispersed systems is different from the dispersion medium viscosity (pure liquid). To establish these deviations in Newtonian liquids, the following relations are used the relative viscosity r/ = rj/rj (rj = viscosity of dispersed system, = viscosity of pure dispersion medium), the specific viscosity = (jj-jJq)/)Jq = or viscosity number t/jp/c (c = dispersed phase concentration) and limiting viscosity number [t ] = limj. Q r/splx- In dispersed systems, where the dispersed phase particle sizes are comparable to the molecular dimensions of the dispersion medium, the following equation can be used Imj =. ln jj + X2.bit)2, where t , and t/j = viscosities of components, X[ and X2 = their mole fractions. 

The specific surface, a, is also relatively insensitive to the duid dynamics, especially in low viscosity broths. On the other hand, it is quite sensitive to the composition of the duid, especially to the presence of substances which inhibit coalescence. In the presence of coalescence inhibitors, the Sauter mean bubble size, is significantly smaller (24), and, especially in stirred bioreactors, bubbles very easily circulate with the broth. This leads to a large hold-up, ie, increased volume fraction of gas phase, 8. Sp, and a are all related... 

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