Relative viscosities

The relative viscosity 77/770- This is obtained from Eq. (9.11) simply by dividing both sides of the equation through by the viscosity of the solvent (B = B/77o,etc.) ... 

Relative viscosity Relaxation Relaxation spectrometry Relays... 

Viscosity Index Improvers. VI improvers are long-chain, high molecular weight polymers that increase the relative viscosity of an oil at high temperatures more than at low temperatures. In cold oil the molecules of the polymer adopt a compressed coiled form so that the affect on viscosity is minimized. In hot oil the molecules swell, and interaction with the oil produces a proportionally greater thickening effect. Although the viscosity of the oil—polymer mixture decreases as the temperature increases, viscosity does not decrease as much as the oil alone would decrease. 

Rheology. Flow properties of latices are important during processing and in many latex appHcations such as dipped goods, paint, inks (qv), and fabric coatings. For dilute, nonionic latices, the relative latex viscosity is a power—law expansion of the particle volume fraction. The terms in the expansion account for flow around the particles and particle—particle interactions. For ionic latices, electrostatic contributions to the flow around the diffuse double layer and enhanced particle—particle interactions must be considered (92). A relative viscosity relationship for concentrated latices was first presented in 1972 (93). A review of empirical relative viscosity models is available (92). In practice, latex viscosity measurements are carried out with rotational viscometers (see Rpleologicalmeasurement). 

The viscosity ratio or relative viscosity, Tj p is the ratio of the viscosity of the polymer solution to the viscosity of the pure solvent. In capillary viscometer measurements, the relative viscosity (dimensionless) is the ratio of the flow time for the solution t to the flow time for the solvent /q (Table 2). The specific (sp) viscosity (dimensionless) is also defined in Table 2, as is the viscosity number or reduced (red) viscosity, which has the units of cubic meters per kilogram (m /kg) or deciUters per gram (dL/g). The logarithmic viscosity number or inherent (inh) viscosity likewise has the units m /kg or dL/g. For Tj g and Tj p, the concentration of polymer, is expressed in convenient units, traditionally g/100 cm but kg/m in SI units. The viscosity number and logarithmic viscosity number vary with concentration, but each can be extrapolated (Fig. 9) to zero concentration to give the limiting viscosity number (intrinsic viscosity) (Table 2). 

Viscosity—Concentration Relationship for Dilute Dispersions. The viscosities of dilute dispersions have received considerable theoretical and experimental treatment, partly because of the similarity between polymer solutions and small particle dispersions at low concentration. Nondeformable spherical particles are usually assumed in the cases of molecules and particles. The key viscosity quantity for dispersions is the relative viscosity or viscosity ratio,... 

The relative viscosity of a dilute dispersion of rigid spherical particles is given by = 1 + ft0, where a is equal to [Tj], the limiting viscosity number (intrinsic viscosity) in terms of volume concentration, and ( ) is the volume fraction. Einstein has shown that, provided that the particle concentration is low enough and certain other conditions are met, [77] = 2.5, and the viscosity equation is then = 1 + 2.50. This expression is usually called the Einstein equation. 

Fig. 13. Relative viscosity vs volume fraction for a typical dispersion ( where (-) represents the Einstein relationship [77] = 2.5, and (—...

The deviation from the Einstein equation at higher concentrations is represented in Figure 13, which is typical of many systems (88,89). The relative viscosity tends to infinity as the concentration approaches the limiting volume fraction of close packing ( ) (0 = - 0.7). Equation 10 has been modified (90,91) to take this into account, and the expression for becomes (eq. 11) ... 

Fig. 1. Relative viscosity data for conventional petroleum, heavy oil, and bitumen.

Inherent viscosity, ASTM D1234 Relative viscosity, ASTM D1234 K value, (DIN 53726) Af X 10-" Af X 10-"... 

Walue Relative viscosity Walue Relative viscosity... 

Viscosities of Gases Coordinates for Use with Fig. 2-32.. . . Nomograph for Determining a) Absolute Viscosity of a Gas as a Function of Temperature Near Ambient Pressure and (h) Relative Viscosity of a Gas Compared... 

Solvent can affect separation in two different ways. Because water is a better solvent for these four columns than water/methanol, based on the swelling or void volume of the columns in Table 17.9, the separation should be better in water than in water/methanol. The relative viscosity of a 0.5% PEO standard from Aldrich (Lot No. 0021kz, MW 100,000) in water and in water/methanol with 0.1 M lithium nitrate is 1.645 and 1.713, respectively. This indicates that the hydrodynamic volume of PEO in water is smaller than in water/methanol. The difference in hydrodynamic volume between two PEO standards should also be larger in water/methanol than in water. Hence, the separation for PEO should be better in water/methanol than in water. The results in Table 17.8 indicate that separation efficiency is better in water than in water/methanol... 

An estimation of the multiphase viscosity is a preliminary necessity for convenient particle processing. For particle-doped liquids the classical Einstein equation [20] relates the relative viscosity to the concentration of the solid phase ... 

Figure 2 Variation of relative viscosity with particle volume fraction.

T r = Relative viscosity [17] = Intrinsic viscosity Pi = Liquid density (Kg/m )... 

In decreasing order of exactness, methods of defining viscosity include absolute (poise) viscosity kinematic viscosity in centistokes relative viscosity in Saybolt universal seconds (SUS) and SAE numbers. 

For most practical purposes, it will serve to know the relative viscosity of the fluid. Relative viscosity is determined by timing the flow of a given quantity of the hydraulic fluid through a standard orifice at a given temperature. There are several methods in use. The most acceptable method in the United States is the Saybolt viscosimeter. Figure 40.17. 

Conventionally fillers are divided into reinforcing, active, and inert ones. The reinforcing class includes mainly fibrous materials. Disperse fillers may also perform the reinforcing function, and then they are called active. For the criterion of activity of a filler it has been proposed to employ, for example, the extent of variation of the relative viscosity of the melt or solution caused by introduction of a filler [23] — the greater the variation the better the affinity between the polymer and the filler. 

Rheological experiments have shown that the relative viscosity of compositions filled with the above materials is an exponential function of filler content by volume. The impact of an otherwise constant quantity of filler increases in the series FP — LDP — SDP, i.e., symbatically with the probability of particle comminution in the plasticization process. This effect is most clearly apparent for... 

For scaly fillers the increase of relative viscosity with filler concentration is not as pronounced as in case of fibrous fillers [177,178]. Owing to filler orientation, the flow curves for systems with different concentrations of a fibrous and a scaly filler may merge together at high shear rates [181]. In composites with a dispersed filler the decrease of the effective viscosity of the melt with increasing strain rate is much weaker. 

Note that, apart from the filler particle shape and size, the molecular mass of the base polymer may also have a marked effect on the viscosity of molten composites [182,183]. The higher the MM of the matrix the less apparent are the variations of relative viscosity with varying filler content. In Fig. 2, borrowed from [183], one can see that the effect of the matrix MM on the viscosity of filled systems decreases with the increasing filler activity. In the quoted reference it has also been shown that the lg r 0 — lg (MM)W relationships for filled and unfilled systems may intersect. The more branches the polymer has, the stronger is the filler effect on its viscosity. The data for filled high- (HDPE) and low-density polyethylene (LDPE) [164,182] may serve as an example the decrease of the molecular mass of LDPE causes a more rapid increase of the relative viscosity of filled systems than in case of HDPE. When the values (MM)W and (MM)W (MM) 1 are close, the increased degree of branching results in increase of the relative viscosity of filled system [184]. 

As established in [214], in roller-mixed PVC-based composites one observes a much better uniformity of filler distribution over the matrix volume the relative viscosity is thereby considerably reduced. That is, for a fixed filler content, the viscosity of a system with agglomerates is always higher than that of the well-dispersed sample. 

Finishing of the filler surfaces may also greatly affect the system viscosity. For mica-filled PP [31] and various thermoplastics filled with calcium carbonate [202, 261] it was shown that the relative viscosity of filled systems was lower than that of systems which contained equivalent quantitied of unfinished filler. Note that in contrast to viscosity in shear, the viscosity in stretching is higher for systems with treated filler [202]. 

Aliphatic PAs dissolve well in m-cresol, formic acid (85-90%), and concentrated sulfuric acid (96-98%). Industry usually determines the relative viscosity ((/rd) of a 1% solution in concentrated sulfuric acid. The inherent viscosity (r/inh) is... 

PA-4,6 salt is prepared from adipic acid and 1,4-tetramethylenediamine as described for the PA-6,6 salt (Example la). PA-4,6 salt (20 g), 2 mL water, and 0.2 mL 1,4-tetramethylenediamine (2.1 mol % excess) are added to a 100-mL glass container in an autoclave. The autoclave is flushed with nitrogen, closed, and given a starting nitrogen pressure of 5 bar. The autoclave is heated over a period of 60 min to 180° C and maintained at that temperature for 100 min, when the pressure is increased to about 8 bar. The pressure is then gradually released, the reaction mass cooled, and the material removed from the autoclave. The prepolymer is crushed into small particles (0.1—0.2 mm) (see Example lb). This prepolymer has a relative viscosity (r]rd) of 1.3 as measured in 96% sulfuric acid (1% solution at 25° C). 

Figure 3.24 Influence of PA-6 polymerization process on relative viscosity as function of reaction time (i) atmospheric in VK column (ii) prepolymerization atmospheric followed by water removal (iii) prepolymerization at elevated pressure followed by water removal.31...

Recycling, 529-574 closed-loop, 534 history of, 529-531 of urethane materials, 207-208 Reinforced polyamides, 139 Relative viscosity, 161 REPETE, 532 Repolymerization, 559-560 of EG and DMT, 561-562 Research... 

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