Viscosity, AES

The constant A is tjQ, and T and To are temperamres (°C). The VFT equation provides a good fitting of data over a wide range of temperamres. Anyhow, near the lower end of the transformation region, it should be used with caution because the activation energy of viscosity AE ) is almost constant and hence viscosity values may be overestimated. When To 0, then the VFT equation changes to the Arrhenian equation, i.e.. 

Table 6 shows a comparison of commercially produced C, 4 LAS samples in a current North American light-duty liquid (LDL) formulation containing more than 20% LAS together with alcohol ether sulfate (AES), amide, and hydrotrope. The highest viscosity is observed with the high 2-phenyl/low DATS sample, whereas the high 2-phenyl/high DATS sample had the lowest viscosity. The DATS provides the dual function of surfactant and hydrotrope. 

FIG. 9 Viscosity-reducing effect of C12 average tetralinsulfonate on C12 average LAS (blended from pure homologs) in a 24% LAS/6% AES/2% amide/5% SXS dishwashing liquid. 

TABLE 6 Effect of DATS Content on Viscosity of an LAS/AES/Amide LDL Formulation... 

Applications Over the last 20 years, ICP-AES has become a widely used elemental analysis tool in many laboratories, which is also used to identify/quantify emulsifiers, contaminants, catalyst residues and other inorganic additives. Although ICP-AES is an accepted method for elemental analysis of lubricating oils (ASTM D 4951), often, unreliable results with errors of up to 20% were observed. It was found that viscosity modifier (VM) polymers interfere with aerosol formation, a critical step in the ICP analysis, thus affecting the sample delivery to the plasma torch [193]. Modifications... 

DCP-AES can be used for high-viscosity matrices, slurries, etc. Organic solvents and acids can be handled without problems. Sample preparation is simpler than for ICP. Operating costs are much lower than for ICP-AES. Table 8.32 compares DCP-AES to ICP-AES and FAAS Table 8.33 shows typical detection limits. DCP and its applications were reviewed [208]. 

A further advantage of this system is that it can easily he integrated with a commercial ICP-AES or ICP MS instrument without software or electronic interface modifications. It will operate rehably for a wide range of viscosities and has apphcations not only in the oil industry but also for highly concentrated samples from other areas. It uses standard autoanalyser principles similar to the Technicon Auto Analyzers. 

Physical interferences in FLAA analysis are of the same nature as the ones in ICP-AES analysis high dissolved solids contents in samples change the sample viscosity and alter the aspiration rate. 

D 5293 in Used Lubricating Oils and Determination of Selected Elements in Base Oils by ICP-AES Apparent Viscosity of Engine Oils Between -5 and -30 °C Using the Cold-Cracking Simulator... 

The ICP-AES and ICP-MS techniques may also suffer from matrix effects, such as spray chamber effects caused by the different viscosity of the samples and the calibration standards. The careful choice of internal standards can reduce this problem. The effects caused by high amounts of easily ionized elements may be solved by internal standardization or by the use of matrix-matched calibration curves. An additional specific problem with ICP-AES is the risk of spectral overlaps. 

The choice of the appropriate mineral acid and oxidant depends on the final analytical technique to be used. For instance, HC1 is not recommended for furnace analysis as it can cause Cl interferences, while H2S04 is not desirable with ICP-AES or ICP-MS because of transport interferences derived from its viscosity. With ICP-MS HNO3 and H202 are preferred since the effect of polyatomic interferences is minimal as compared with HC1, HC104 and H2S04, which introduce polyatomic ions such as C10+ and SO+ [28-32]. In any case, in order to minimize corrosion of the metal sampler and skimmer cones with ICP-MS, final sample solutions should not contain high acid concentrations (e.g., above 10 percent for HNO3). 

Thus measurements of the viscosity 9 (0,7) over a range of temperature allow determination of f(0,T) as a function of T, provided the value of /(0,T) at a certain temperature T is known from other source. For this purpose we may utilize the measurement of viscosity as a function of diluent concentration at the given T ] the substitution of such data into Eq. (40) may lead to the determination of the required f(0,T ). It is to be expected that, if the free volume theories of viscosity and diffusion developed above are at all correct, the values of /(0,7) thus derived from y data should agree with those obtained from ae data by application of Eq. (40) and also with those from DT data analyzed in terms of Eq. (36). 

V 14. Molar intrinsic viscosity J K -M - 4.2Z Intrinsic viscosity parameter K1/2 Ae... 

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