Single-point intrinsic

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... 

Figure 7. Single Point Intrinsic Capability of the Viscometer.

The molecular weight of SAN can be easily determined by either intrinsic viscosity or size-exclusion chromatography (sec). Relationships for both multipoint and single point viscosity methods are available (18,19). Two intrinsic viscosity and molecular weight relationships for azeotropic copolymers have been given (20,21) ... 

Frequently occurs that extrapolations do not have a common value at their origin ordinates. These deviations may be caused by inadequate lineal extrapolations. The above mentioned is the routine method used for [q] determination. The procedure is laborious and consumes a considerable amount of time and reactive because of this, several equations were developed which estimate intrinsic viscosity at one single concentration and do not require a graphic. They are known as "single-point" methods. 

Chee K.K. A critical evaluation of the single-point determination of intrinsic viscosity. Journal of Applied Polymer Science 34, 3 (1987) 891-899. 

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

LALS) in THF and the intrinsic viscosity of five of the samples was measured by the single point method. Combining the LALS data with the intrinsic viscosity work allows one to obtain the Mark-Houwink constants, and a, by plotting log[77] vs logMw. For PIPTBK, and a in THF at 25° were found to be 5xlO-3 ml/g and 0.75 respectively. 

Where an intrinsically safe circuit is earthed by construction at the place of the field device (e.g. this is frequently the case using thermocouples), an Ex i-isolator with galvanic isolation shall be inserted. The reason is that intrinsically safe circuits shall be earthed at one single point only. 

Intrinsically safe circuits may be isolated from earth or connected to the equipotential bonding system at one single point, if this system covers the total installation area of the intrinsically safe circuits. 

Molecular Weight. The viscosity average molecular wei t of the homopolymer and copolymers was determined from single point determinations of viscosity of a 0.25% solution in Fisher purified cyclohexane at 30.0 + 0.01° C. The molecular wei t is calculated from the intrinsic viscosity, [q], using the relationship ( ... 

Masuelli, M. A., Illanes C. I. 2014. Review of the characterization of sodium alginate by intrinsic viscosity measurements. Comparative analysis between conventional and single point methods. Int. J. 

Zhao, Z. H., Sun, H. Z., Sun, M. K. 2002. Single point method to determinate the intrinsic viscosity of carboxymethylated chitosan. Marine Fisheries Research Chinese) 23 41-43. 

The most commonly used type of viscosimeter for the determination of the intrinsic viscosity or for single point measurements is the capillary viscosimeter. As the reproducibility with this type of viscosimeter depends on the clean execution of the measurement, a detailed description of the proceedings for a viscosimetric measurement is given below. 

Single point measurements are commonly used to determine the intrinsic viscosity via the so-called Fikentscher K-value. This method is, as shown in Determination of the intrinsic viscosity by viscosimetric measurements in Chap. 4, only applicable under very special conditions and should not be used anymore. Generally, single point measurements only serve for the determination of a viscosity value. 

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