Gel strength, measurement

For some dipped work, wet gel strength measurement is carried out, where the gel is deposited onto preformed, tissue paper dumbeUs, and the load necessary to break the dumbeU-shaped test piece is measured. 

Figure 3. Loading (left) and score (right) plots from a PCA on chemical data measured on the pectins (%DE=degree of esterification, %DA=degree of amidation, %DFA=100-%DE-%DA, Transp=transparency, Cal-Ca4 and SAG are gel strength measures).

The DM interacts with gel pH to determine the maximum gel strength measurement. In the typical curve shown in Figure 1, the optimum firmness occurs at higher pH values for higher IM pectins (7, 47). 

Internal gel strength measurements are currently under review. 

In Table 2 are given the results of gel strength measurements of 1 1 mixtures of alginate and pectin at pH... 

TABLE 2. Gel Strength measurements of 1 1 combinations of different alginates with Mexpec-tin RS400 at pH 2.9. Total polymer concentration is 1.2% (v/w). 

Often gel strength measurements on different samples require variation in the vacuum level to make the readings in a timely fashion. Thus, a conversion of the flowing time values to a common vacuum is required to evaluate the gel strength results. As an approximation, the gel viscosity can be assumed to exhibit a power law behavior. Using this assumption, the conversion of the flowing time between different vacuum levels is given below ... 

The proper design of a profile modification treatment requires measurement of the permeability reduction caused by a given gel system. Core tests have shown that relative gel strength measurements with the capillary viscometer correlate with permeability reduction--Increasing gel strength develops higher residual resistance factors. 

Additionally, gel strength (0) measurements were read directly from the deflection scale. When making gel strength measurements, force was applied manually by turning the gel knob and observing the maximum reading on the deflection scale before the gel broke. 

Superabsorbents. Water-sweUable polymers are used extensively in consumer articles and for industrial appUcations. Most of these polymers are cross-linked acryUc copolymers of metal salts of acryUc acid and acrylamide or other monomers such as 2-acrylamido-2-methylpropanesulfonic acid. These hydrogel forming systems can have high gel strength as measured by the shear modulus (134). Sometimes inorganic water-insoluble powder is blended with the polymer to increase gel strength (135). Patents describe processes for making cross-linked polyurethane foams which contain superabsorbent polymers (136,137). 

Gel Strength. The gel strength of oil-base muds is measured with a direct indicating viscometer exactly like that of water-base muds. 

Young moduli and breaking strength (measured by an Instron apparatus) of pectin gel and of extruded citrus fibre at different concentrations ( 60% sucrose, pH 3)... 

The oranges were washed, chopped in a meat mincer and homogenised by a Fryma mill. Water (0.6 volumes) were added before the slurry was heat treated by steam injection at 100°C for 2 minutes. The enzyme treatment was carried out for 1 hour at 40°C with 10 lU/g slurry of PME and 25 pg enzyme protein/g slurry of the other enzymes for each of the enzymes. The gelated orange slurry were treated at 85°C for 3 minutes to inactivate the enzymes before the strength of the gel was measured by a SMS TeJrture Analyser TA-XT2 (Stable Micro Systems, XT. RA Dimensions, Operations Manual versions) by compression analysis using a flat cylinder (20 mm dia.) with a speed of 2 mm/s. The force to provide a 20% compression was recorded. 

Different product sorts (20-22,24-26) are marked in the score plot of spectral NIR measurements (Fig. 4). Sorts 23 and 31 are in separate classes outside the range of this plot. A gradient is seen in the plot, indicating the chemical differences among the sorts the %DE are increasing in the 20->25/26 direction while the opposite holds for the Ca-based gel strength measm-ements. 

The increase in gel strength with increase in bentonite concentration above the gel point is consistent with the increase in yield value and modulus. On the other hand, the limited creep measurements carried out on the present suspension showed a high residual viscosity Oq of the order of 9000 Nm s when the bentonite concentration was 45g dm. As recently pointed out by Buscall et al (27) the settling rate in concentrated suspensions depends on 0. With a model system of polystyrene latex (of radius 1.55 vim and density 1.05 g cm ) which was thickened with ethyl hydroxy ethyl cellulose, a zero shear viscosity of lONm was considered to be sufficient to reduce settling of the suspension with = 0.05. The present pesticide system thickened with bentonite gave values that are fairly high and therefore no settling was observed. 

An empirical measure of gel rigidity is the measurement of gelatin gel strength, also known as Bloom strength. The procedure is described in the It... 

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