Viscosity determining

To obtain the Saybolt Universal viscosity equivalent to a kinematic viscosity determined at FF., multiply the equivalent Saybolt Universal viscosity at lOOT. by 1 + (t — 100) 0.000064 e.g., 10 centistokes at 210T are equivalent to 58.91 X 1.0070, or 59.32 Saybolt Universal Viscosity at 210°F. 

This equation is the basis for viscosity determination by measuring flow times through a capillary. It can also be used to describe a single liquid at two different temperatures, as required for Eq. (4.63). Combining Eqs. (4.63) and (4.64) yields... 

Since viscometer drainage times are typically on the order of a few hundred seconds, intrinsic viscosity experiments provide a rapid method for evaluating the molecular weight of a polymer. A limitation of the method is that the Mark-Houwink coefficients must be established for the particular system under consideration by calibration with samples of known molecular weight. The speed with which intrinsic viscosity determinations can be made offsets the need for prior calibration, especially when a particular polymer is going to be characterized routinely by this method. 

Laminates. Laminate manufacture involves the impregnation of a web with a Hquid phenoHc resin in a dip-coating operation. Solvent type, resin concentration, and viscosity determine the degree of fiber penetration. The treated web is dried in an oven and the resin cures, sometimes to the B-stage (semicured). Final resin content is between 30 and 70%. The dry sheet is cut and stacked, ready for lamination. In the curing step, multilayers of laminate are stacked or laid up in a press and cured at 150—175°C for several hours. The resins are generally low molecular weight resoles, which have been neutralized with the salt removed. Common carrier solvents for the varnish include acetone, alcohol, and toluene. Alkylated phenols such as cresols improve flexibiUty and moisture resistance in the fused products. 

In the equation referred to above, it is assumed that there is 100 percent transmission of the shear rate in the shear stress. However, with the slurry viscosity determined essentially by the properties of the slurry, at high concentrations of slurries there is a shppage factor. Internal motion of particles in the fluids over and around each other can reduce the effective transmission of viscosity efficiencies from 100 percent to as low as 30 percent. 

Amorphous bisphenol-A polyarylates are soluble in dioxane and in chlorinated solvents such as CH2C12, 1,2-dichlororethane, 1,1,2-trichloroethane, and 1,1,2,2-tetrachloroethane while semicrystalline and liquid crystalline wholly aromatic polyesters are only sparingly soluble in solvents such as tetrachloroethane-phenol mixtures or pentafluorophenol, which is often used for inherent viscosity determinations. 

Curvale, R.A., Cesco, J.C. 2009. Intrinsic viscosity determination by "single-point" and "double-point" equations. Applied Rheology 19, 5, 53347. 

Intrinsic viscosity determined in m-cresol at 3 °C insoluble in m-cresol... 

The synthesis of linear 4 —> 1-a-D-glucans from D-glucopyranosyl phosphate by the action of phosphorylases has been shown by comparison of results of methylation and end-group assay and viscosity determination,209 and by potentiometric, iodine titrations82 on the product. The chain length of the enzymic product (100 to 200 D-glucose units) is less than that of the natural component. Whether this is due to impure enzymes cannot yet... 

Alpha amylases cause a rapid fragmentation of starch with an accompanying marked decrease in viscosity of the starch solutions. Therefore, viscosity determinations may be used to follow the early stages in the hydrolysis of starch by these amylases. Afthough this type of measurement is of considerable importance for certain industrial applications, it has not been used to any great extent in investigations with pancreatic amylase. 

As a result of the various methods for viscosity determination, it is not surprising that much effort has been spent on interconversion of the several scales, especially converting Saybolt to kinematic viscosity (ASTM D2161),... 

The Saybolt universal viscosity equivalent to a given kinematic viscosity varies slightly with the temperature at which the determination is made because the temperature of the calibrated receiving flask used in the Saybolt method is not the same as that of the oil. Conversion factors are used to convert kinematic viscosity from 2 to 70 cSt at 38°C (100°F) and 99°C (210°F) to equivalent Saybolt universal viscosity in seconds. Appropriate multipliers are listed to convert kinematic viscosity over 70 cSt. For a kinematic viscosity determined at any other temperature, the equivalent Saybolt universal value is calculated by use of the Saybolt equivalent at 38°C (100°F) and a multiplier that varies with the temperature ... 

Figure 3.8 Intrinsic viscosity determination for the data in Tables 3.3 and 3.4...

DCE characterization can be conveniently carried out by H-NMR, elemental analysis, pH, and viscosity determination. The trimethyl ammonium and dimethyldodecyl ammonium content were evaluated, as well as an indirect percent nitrogen (% N), by H-NMR (Gemini 200 NMR, H/ C dual probe at 25°C, as 3.3% solutions in de-DMSO). The %N via H-NMR correlated extremely well with elemental analysis (Tables 3 and 4). 

K. Ito, T. Kato and T. Ona, Rapid viscosity determination of waterborne automotive paint emulsion system by FT-Raman spectroscopy, Vib. Spectrosc., 35, 159-163 (2004). 

Viscosity Determinations. The viscosity determinations were conducted at 60 C with a Haake Rotovisco RV12 viscometer or at 90 C with a Nametre viscometer. 

The sample fluid could be any neat liquid or a sample of polymer solution. Under favorable conditions, a single viscosity determination on a polymer solution at high dilution can provide a direct measure of the polymer intrinsic viscosity, without the need of polymer concentration extrapolation. With this viscometer used as a continuous viscosity detector for SEC, it is possible to achieve SEC molecluar weight calibration by way of the universal SEC calibration methodology without the need of molecular weight standards for the unknown polymers. 

Figures 2 and 5 illustrate two different configurations of the viscometer that can be used in batch sanple viscosity determinations.

Due to the high sensitivity of the viscometer, accurate readings of viscosity responses can be made with sample h gi values much less than 1.1. Therefore, saitple solutions of very low concentration can be analyzed in the viscometer to produce a single point intrinsic viscosity determination without the need of concentration extrapolation. As shown in Figure 7 for a polystyrene saitple, any h- u determination at the value of... 

The polymer samples studied here fall into three distinct categories. Data from two sample populations have been combined in the SAN copolymer study. A group of SAN materials having compositions ranging from 42 (wt)% AN to 82% AN were polymerized and characterized quite some time ago (1972), with intrinsic viscosities determined only in DMF. Very recently, a second group of SAN s with compositions from 5 (wt)% to 48% AN, as well as one sample of polystyrene (0% AN), were polymerized and characterized, with intrinsic viscosities determined in DMF, THF, and MEK. These two populations are differentiated in the Results section by the designations "old data" and "new data". The third category of samples is that of S/MA copolymers and S/MA/MM terpolymers, with intrinsic viscosities measured only in MEK. 

High-boiling-point compounds such as asphaltenes, branched hydrocarbons with molecular weights greater than 300, and alkylated naphthenes can increase fuel viscosity. If present in fuel, they can be detected indirectly through either ASTM D-86 distillation end point temperatures or by high ASTM D-445 viscosity determinations. 

Utilize low-temperature viscosity determinations rather than pour point values to establish low-temperature handling limits on oils possessing this characteristic phenomenon. 

Viscosity — Determine the viscosity (efflux) in accordance with Method No 212.1 which is described in Specification MIL-STD-650. See 6.6... 

The TA Instruments CSL2 rheometer can perform low frequency oscillatory measurements as well as steady-state viscosity determinations, even though it has a simple mechanical system. The sinusoidal wave form is generated mathematically in the computer rather than with an electromechanical drive system. The stress is controlled, and the resulting strain is determined and stored in memory. The computer analyzes the wave form and calculates the viscosity and elasticity of the specimen at the frequency of the test. As of this writing (1996), the oscillation software covers a frequency range of 10-4 -40 Hz. This range could be increased as faster software and computers become available. 

Figure 4.13 is a plot of the viscosity determined by the sensor at each of the four positions in the thick laminate during cure in the autoclave. The FDEMS sensor data show that the middle ply achieves its first viscosity minimum 20 minutes after the plies on the surface of the... 

The solution behavior of poly(amic acids) was until recently, probably the least understood aspect of the soluble polyimide precursor. However, the advent of sophisticated laser light scattering and size exclusion chromatography instrumentation has allowed elucidation of the solution behavior of poly(amic adds). In the early days of polyimide chemistry, when most molecular weight characterization was based on viscosity determinations, a decrease in viscosity was associated with molecular weight degradation [15, 28, 29]. Upon combination of the two monomers an increase in the viscosity to the stoichiometric equivalence point is observed, followed by a decrease in the solution viscosity as a... 

---