Reduction of viscosity

Many microbial polysaccharides show pseudoplastic flow, also known as shear thinning. When solutions of these polysaccharides are sheared, the molecules align in the shear field and the effective viscosity is reduced. This reduction of viscosity is not a consequence of degradation (unless the shear rate exceeds 105 s 1) since the viscosity recovers immediately when die shear rate is decreased. This combination of viscous and elastic behaviour, known as viscoelasticity, distinguishes microbial viscosifiers from solutions of other thickeners. Examples of microbial viscosifiers are ... 

Yet, some authors reported an increase, instead of reduction of viscosity after finishing treatment of filler [266, 267]. Plueddeman in [268] noted that increase or decrease of melt viscosity with finishing agents depends on what is the resultant reaction of the filler, agent and matrix - neutral, acid or basic. The viscosity may be optimized by using the right formulation. For example, agents with basic... 

Endo-pectinases were determined by reduction of viscosity of a 1% (w/v) pectin solution at 30 C and pH 4.2 using an Ostwald viscosimeter as previously described (9). One unit was defined as the amount of enzyme which reduced the initial viscosity of the solution by 50%. 

The total activity of the enzymatic mixture was determined from the percentage reduction of viscosity [12] during the depolymerization of solutions, buffered at different pH values, containing 1 % (w/v) of the polygalacturonic acid or 0.5% (w/v) of pectin. A Cannon-Fenske viscosimeter, (ASTM series n° 150) kept at the constant temperature of 25 °C, was used to carry out the tests. 

Figure 1. Trend of the concentration of the reducing ( ) and unsatured ( ) groups and percentage reduction of viscosity (A) of the pectin solution as a function of the reaction time, at pH 6.0.

Pulp from ripe Golden apple was pressed in a mortar and filtered, thus obtaining a cloudy and dense juice. Potassium metabisulphite was added as antioxidant at a final concentration of 0.15 mg/mL. The pH of the prepared apple juices was 4.1 4.3. Depectinisation experiments were carried out loading the juice in the packed bed reactor and recycling for 30 min at 25 "C. The reaction mixture was then collected and the percentage reduction of viscosity measured as above described. The y-alumina spheres were abundantly washed with distilled water before performing the successive batch reaction. 

Figure 2 reports the trend of the percentage reduction of viscosity as a function of the concentration of the reducing groups for the depolymerisation of pectin at pH 3.0... 

The immobilised Pectolyase Y-23 was used to perform consecutive depectinisations of a cloudy apple juice in batch reactions. After five reaction cycles, the percentage reduction of viscosity was greater than 90%. The viscosity of the apple juice feed through a bed of inactive y-alumina spheres remains unchanged thus confirming that the viscosity loss attributable to pectin adsorption on the carrier is negligible. The alcohol tests, performed on the juices previously treated with the... 

In the approach followed in this invention [29], a biocatalytic agent converts the sulfur heterocycles into different molecules that do not exhibit the hydrophobic interactions. This is achieved by selectively cleaving carbon-sulfur bonds. The selectivity of the biocatalytic agent employed is limited to the carbon-sulfur bonds and no attack to the carbon-carbon skeleton was reported. Thus, it is expected that the proposed biocatalytic reduction of viscosity would not diminish the fuel value of the treated petroleum liquids. The biocatalyst employed consisted of the strain ATCC No. 53968 (see Section 20 and references therein), in an aqueous culture conventionally prepared by fermentation under aerobic conditions. The fermenting bioreactor is fed with a suitable nutrient medium, which comprises a conventional carbon source (dextrose and glycerol are recommended carbon sources. To confer maximal biocatalytic activity for the desired cleavage of organic C—S bonds, the bacteria was kept in a state of sulfur deprivation. 

Asvarujanon, P., Ishizuka, S., and Hara, H. (2004). Inhibitory effects of psyllium on rat mineral absorption were abolished by reduction of viscosity with partial hydrolysis. Biosci. Biotechnol. Biochem. 68,1737-1742. 

It turned out that these two grades are behaving differently. The low viscosity grade shows a reduction of viscosity with the number of processing cycles. In contrast, the high viscosity grade shows an increase of melt viscosity after repeated processing. 

Prolonged nitration favours the processes of degradation and oxidation, and hence also the reduction of viscosity. Schur and Hoos [78a] have nitrated wood pulp cellulose at various temperatures to attain results as follows (Table 49). 

Thus in the instance of 1% solution exposed for an interval of 4 hr to the action of light the decrease in viscosity is 0.3-0.7%. With 10-20% solutions, on the other hand, the reduction in viscosity during the same period is 25.0-34.2%. Mine s experiments showed that in solutions of low viscosity the reduction of viscosity could remain unobserved. Claesson and Wettermark [92a] investigated the irradiation of solutions of cellulose nitrate with light of wave-length 253 rafi. The depolymerization was followed viscosimetrically and the chain breakage was found to obey the course predicted theoretically for a random process with a quantum yield of 0.01-0.02. 

Liauid 1. heating reduction of viscosity, thereby speeding... 

Rozenberg et al. (51) used the reaction shown in equation 35 to explain the large increase in the viscosity of the reaction mixture that they observed after most of the monomer had polymerized. As evidence they offered the observation that the addition of an amount of metha-nolic KOH comparable to the number of active centers caused a marked reduction of viscosity. They associated this with a breakdown of the product of equation 35. Sims (37) has made similar observations. He suggests that the breakdown may be associated with a hydrolysis of the phosphate linkages in the chain of the final product shown in equation 8. Equation 6 a suggests that the explanation for Rozenberg s observations may be similar to Sims, i. e. a hydrolysis of borate esters occurs. 

Insofar as liquid solvents are concerned, the most important factor governing / is viscosity 77, as the Stokes equation clearly demonstrates. Therefore any systematic effort to increase separation speed requires close attention to viscosity, with an emphasis on finding solvents and conditions for which viscosities are minimal. The reduction of viscosity can be pursued systematically in place of a hit or miss search for low viscosity solvents. The approach below was developed by the author and his colleagues [32] for use in optimizing size-exclusion chromatography, but the conclusions are generally applicable to separations. 

Figure 4.11 is a useful guide for the reduction of viscosity and thus of friction coefficient /. It is clear from the figure that small increases in the temperature relative to the boiling point can lead to substantial decreases in V-... 

For rayon production, a controlled cleavage of the cellulose molecule is required to reduce the viscosity of the cellulose xanthate so that it can be forced through fine spinnerets. A similar reduction of viscosity is required for cellulose which will be sprayed as a lacquer. This cleavage is brought about by the air oxidation of alkali cellulose, and the process is speeded by the addition of a few parts per million of a transition metal compound which functions as an oxidation catalyst. 

Figure 1. Reduction of viscosities of heavy crude oils and bitumens by conversion to oil-in-water emulsions.

The compositions of different fillers are easier to process. Figure 16.13 shows that replacement of part of calcium carbonate by microspheres results in reduction of viscosity. Similar reduction of viscosity can be expected in the mixtures of fi-... 

In the absence of any flocculation, the coalescence of an emulsion results in a reduction of its viscosity. At any given volume fraction of oil, an increase in droplet size will result in a reduction of viscosity, and this is particularly the case for concentrated emulsions. Thus, by following the decrease in emulsion viscosity with time, information may be obtained on its coalescence. However, care should be exercised when applying simple viscosity measurements, particularly if flocculation occurs simultaneously (as this results in an increased viscosity). It is possible - at least in principle - to predict the extent of viscosity reduction on storage by combining the results of droplet size analysis (or droplet number) as a function of time with the reduction in viscosity during the first few weeks. 

---