INDEX viscosity effect

Refractive Index. The effect of mol wt (1400-4000) on the refractive index (RI) increment of PPG in ben2ene has been measured (167). The RI increments of polyglycols containing aUphatic ether moieties are negative drj/dc (mL/g) = —0.055. A plot of RI vs 1/Af is linear and approaches the value for PO itself (109). The RI, density, and viscosity of PPG—salt complexes, which maybe useful as polymer electrolytes in batteries and fuel cells have been measured (168). The variation of RI with temperature and salt concentration was measured for complexes formed with PPG and some sodium and lithium salts. Generally, the RI decreases with temperature, with the rate of change increasing as the concentration increases. 

The application of refractive index and differential viscometer detection in SEC has been discussed by a number of authors [66-68]. Lew et al. presented the quantitative analysis of polyolefins by high-temperature SEC and dual refractive index-viscosity detection [69]. They applied a systematic approach for multidetector operation, assessed the effect of branching on the SEC calibration curve, and used a signal averaging procedure to better define intrinsic viscosity as a function of retention volume. The combination of SEC with refractive index, UV, and viscosity detectors was used to determine molar mass and functionality of polytetrahydrofuran simultaneously [70]. Long chain branching in EPDM copolymers by SEC-viscometry was analyzed by Chiantore et al. [71]. 

These systems involve the irradiation of areas in a sheet of organic polymer, made by a vinyl polymerization reaction, to produce a change in refractive index. The effect is attributed to photopolymerization of residual monomer to yield a local increase in density. Diffusion of the monomer in the high-viscosity matrix is slow, as is the physical relaxation of the matrix it-itself, and the full index change takes some time to develop. 

It can be proved that the refractive index of the mixtures depends linearly on the percentage of ethylene glycol. In the S-1 photoreaction both the photoisomerisation steps strongly depend on the absolute viscosity, whereas 3 is very small and stays nearly constant during the photoreaction. Since the determined values of quantum yield fit even for different mixtures of water/ethylene glycol with viscosity adjusted to the same value by variation of temperature (see Fig. 5.53), polarity effects of the solvent will influence the photoreaction less than viscosity effects [178]. 

Willhite and Uhl (1986, 1988) studied the flow of xanthan in Berea cores over the concentration range 500-1500 ppm and over a wide range of flow rates. Starting with equations 6.11 and 6.12 as theoretical models, they compared the experimentally measured in-core power law index and effective mobilities of the polymer solution with the bulk values of n and the viscosity prediction based on the power law equations. They found that the power law exponent for the flow of a xanthan biopolymer through Berea sandstone was larger than the bulk value for polymer concentrations above 500 ppm. Like Teew and Hesselink (1980), they found that the effective polymer viscosities are overestimated by the capillary bundle models. Similar results for the flow of xanthan through unconsolidated sandpacks have been found more recently by Hejri et al (1988). 

We present in this work all pubhshed data on density, refractive index, viscosity, electrical conductivity and surface tension for all systems IL + water and + ethanol covering a broad range of concentrations. For density, refractive index and viscosity the data for mixtures with water or ethanol are very similar, and also their behaviour with concentration is not really dependent of the IL mixed with any solvent (except for its value). Density and refractive index can be deduced one from another using Newton s model, which demonstrates the close relationship between both magnitudes. For electrical conductivity and surface tension, the solvent nature determines the data behaviour obtained. Thus, the electrical conductivity value of the pntre IL for aqueous systems increases up to 10 times, while that increase is halved for ethanol systems. In the case of surface tension the behaviour is completely different depending on the solvent and IL studied. For alkyl-methyl-imidazolium tetrafluoroborate the IL acts like a surfactant in water, and the surface tension value decreases sharply from that of water to that of the pure IL for small concentrations of this last, effect that does not appear for halogenated imidazohum ILs. If we change the water for ethanol, that surfactant like effect disappear, and the surface tension value of the only four ILs measured decreases linearly with the ethanol content down to a common value at about equimolar mixture, and then all data has the same value. 

Practically all lubricating oils contain at least one additive some oils contain several. The amount of additive that is used varies from < 0.01 to 30% or more. Additives can have detrimental side effects, especially if the dosage is excessive or if interactions with other additives occur. Some additives are multifimctional, eg, certain VI improvers also function as pour-point depressants or dispersants. The additives most commonly used in hydrautic fluids include pour-point depressants, viscosity index improvers, defoamers, oxidation inhibitors, mst and corrosion inhibitors, and antiwear compounds. 

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. 

Effect of increase of On viscosity On flow behaviour index On critical shear rate On sharkskin... 

All oils become thinner when heated and thicker when cooled, but some are less sensitive than others to these viscosity/temperature effects. The degree of sensitivity is known as Viscosity Index (VI). Oil is said to have high VI if it displays a relatively small change of viscosity for a given change of temperature. 

In these equations all of the physical properties ate taken at the mean bulk temperature of the fluid (T, + T0)/2, where 7) and T0 are the inlet and outlet temperatures. The difference in the value of the index for heating and cooling occurs because in the former case the film temperature will be greater than the bulk temperature and in the latter case less. Conditions in the film, particularly the viscosity of the fluid, exert an important effect on the heat transfer process. 

Borst JW, Flink MA, van Hoek A, Visser AJWG (2005) Effects of refractive index and viscosity on fluorescence and anisotropy decays of enhanced cyan and yellow fluorescent proteins. JFluoresc 15 153-160... 

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