Viscosity reduction

Both regulatory limits on the amount of organic solvents allowed in paints and advancements in alkyd resin technology have resulted in the development of higher soHds alkyd resins that requke less solvent for dilution and viscosity reduction. In addition, developments of water-reducible alkyds and alkyd emulsions have resulted in alkyd-based paints that requke less organic solvent in thek formulations. 

Among the techniques employed to estimate the average molecular weight distribution of polymers are end-group analysis, dilute solution viscosity, reduction in vapor pressure, ebuUiometry, cryoscopy, vapor pressure osmometry, fractionation, hplc, phase distribution chromatography, field flow fractionation, and gel-permeation chromatography (gpc). For routine analysis of SBR polymers, gpc is widely accepted. Table 1 lists a number of physical properties of SBR (random) compared to natural mbber, solution polybutadiene, and SB block copolymer. 

Fig. 3. Rate of viscosity reduction of cellulose nitrate on digestion in water at 132°C. The viscosities (falling-ball method) were determined in 12.2%...

Although all the techniques are effective, in industrial appHcations there is rarely time to achieve an equiHbrium reduced saturation state (see Filtration), so variables that affect only the kinetics of dewatering and not the equiHbrium and residual moisture are also very important. The most important kinetic variables in displacing the Hquid from the soHd are increases in pressure differentials and viscosity reduction. 

Viscosity Reduction. Equations relating the rate of Hquid flow through a filter cake can be simplified to... 

Use of Surfa.cta.nts, Although the use of steam to improve dewatering is consistently beneficial, the effects of surfactants on residual moisture are highly inconsistent. Additions of anionic, nonionic, or sometimes cationic surfactants of a few hundredths weight percent of the slurry, 0.02—0.5 kg/1 of soHds (50), are as effective as viscosity reduction in removing water from a number of filter cakes, including froth-floated coal, metal sulfide concentrates, and fine iron ores (Table 2). A few studies have used both steam and a surfactant on coal and iron ore and found that the effects are additive, giving twice the moisture reduction of either treatment alone (44—46,49). 

Fully hydrated potassium ion coordinates about 10-11 molecules of water, whereas sodium coordinates about 16-17 molecules [115]. The ionic mobility of potassium is about 50% greater than that of sodium. In simple terms, this means that more of the water in a potassium-catalyzed resin will be available as free water for viscosity reduction and that movement of water from a glue line into the wood will have less effect in moving the adhesive off of the glue line with it. 

One of the most attractive features of TLCPs is their ability to alter the rheology of bulk thermoplastic polymers. Most reports in the academic literature are concerned with viscosity reduction. For example, Siegmann et al. [1] observed a steep viscosity drop when a TLCP... 

A distinct viscosity reduction occurs as a small quantity of TLCP is added to a thermoplastic matrix. This negative deviation effect from the log-additivity rule was ex-... 

Nevertheless, from a practical viewpoint physical reasons for viscosity reduction during the surface treatment of the filler play a minor role first of all the effect of viscosity reduction itself is significant. 

FIGURE 16.2 Mild-mixing conditions do not discriminate between peptizers (P-44 and R-11) and the control compound. While QDI-containing compounds show significant viscosity reduction. 

In fact viscosity reduction of diene elastomer blends with QDI show an optimum based on mixer discharge temperature. Figure 16.13 shows the results of two experiments done on the 16 L scale. The viscosities represent the viscosity of the fourth stage of a multistage mixing experiment. These compounds were 60/40 blends of either BR or SBR with NR and contained 50 phr of N-234 carbon black. 

Apple application e)q)aiments for producing ple juice show a clear benificial effect liumnogalacturonase in combination with a pectinase was added to the process. As can be seen from figure 5 rhamnogalacturonase has a clear positive influence on viscosity-reduction. Rhamnogalacturonase also prevents formation of haze in juices and therefore gives a stable juice. 

Figure 5 Influence of rhamnogalacturonase of different strains on viscosity-reduction in apple- lication-e q)erimaits.

Figure 7. The influence of rhamnogalacturonase (RHG) produced by wild-type and RHG-overproducing Aspergillus strains on viscosity reduction during apple hot-mash liquefaction. Apple mash was incubated with Biopectinase LQ alone ( ) or in combination with RHG, produced by A. aculeatus wild type (O) and transformant strains ( ) and an A. awamoti transformant strain ( ). Data taken from Ref. 6...

Comparison with acoustic cavitation have also shown that hydrodynamically generated cavitation is far more energy efficient i.e. 76.5 J/mL as against 14,337 J/mL needed for sonically generated cavitation, for the same process, i.e., equivalent viscosity reduction. 

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