Viscosity of samples

Process Control. The progress of the alkyd reaction is usually monitored by periodical deterrninations of the acid number and the solution viscosity of samples taken from the reactor. The frequency of sampling is commonly every half-hour. Deterrnined values are plotted against time on semi-1 ogarithmic coordinates, as shown in Figure 4. 

Carboxypolymethylene exhibits a stabilizing effect against separation and viscosity change of a cetyl alcohol-stearic acid-sodium lauryl sulfate system. Samples 1 and 2 are identical, except that the former contains carboxypolymethylene (adjusted to pH 7). Sample 1 shows no separation, while sample 2 shows 13% separation after 6 months. Figure 8 shows the viscosity characteristics of the above samples. The broken line represents the viscosities of sample 1 at different time intervals, and the unbroken line, the viscosities at the same time intervals for sample 2. Apparently the carboxypolymethylene prevents the agglomeration and precipitation of stearic acid, which would result in separation and loss of viscosity. 

As described in the above section, information on the relation between the temperature and the viscosity of sample solutions is indispensable for determining the temperature from the result of PCS measurement. Examples of q(T) obtained by a conventional method [10] are shown in Pigure 8.7. 

Recent advances have greatly decreased the difficulties raised by these cautionary points. In particular, on-line viscosimetry and multi-angle lightscattering make it possible to determine the molecular weight and viscosity of samples as a function of elution volume. With such detectors, effects of solute-column packing interactions become unimportant, since the properties of narrow fractions can be measured. These detectors will be discussed in greater detail below. 

Prior to injection, the prepared sample should be centrifuged for 2 to 3 min in a microcentrifuge to remove any particulate material and to degas the solution. This practice is particularly important if the sample contains protein aggregates or other large particles, and when polymers are used to increase the viscosity of sample and ampholyte solution. 

Viscosities of samples of cellulose were measured as 0.5% solutions in cupriethylenediamine by the viscosity pipet method 28). 

The effect of varying this offset between detectors has been examined (I). The molecular weight averages and bulk intrinsic viscosity of samples... 

DNAse and RNAse 1 pg/ml degradation of nucleic acids, reduce viscosity of sample solution... 

Preliminary studies indicated that PFAP(II) undergoes a loss in molecular weight at temperatures above 149°C (1,2). The degradation process was followed by monitoring the change in solution viscosity of samples aged at 150°C in air. The viscosity exhibited a rapid loss during the first 200 hr, then leveled off to a slower rate. 

Sorption effects by the gel matrix may alter the values of and for certain solutes, and the use of against log plots to select a gel, takes into account neither those effects nor zone spreading in the column, and variations in flow-rate (which could arise, for example, from differences in viscosity of sample and eluant). Taken together these may have an important effect on the separation, and hence on the choice of the best gel for a particular purpose. The behaviour of small molecules on tightly cross-linked gels is profoundly influenced by adsorption, ion exclusion, ion exchange and various other processes which dominate the size differences between solutes. 

Time (min) sample was taken (after initiator addition) Refiactive index of cooled sample, "D Viscosity of sample cPs at 25°C... 

Shown in Figure 6 is a plot of the viscosity of samples 3 and 5 plotted as a function of temperature. The viscosities were measured using an Instron Capillary Rheometer at a shear rate of 450 sec, The extracted solvent solubility parameters for samples 3 and 5 were 8.46 and 8.79 respectively. Figure 6 shows that the... 

Effect of cellulose concentration on complex viscosity of samples with KSCN concentration at 40% and 45% of saturation in ethyiene diamine [57]. 

Fig. 2 Storage modulus, loss modulus, and complex viscosity of sample J1 at 30 °C...

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