Viscosity-average

Table 1.5 also includes two additional types of molecular weight average besides those already discussed. The following remarks describe some features of these two, the z-average molecular weight, and the viscosity average ... 

The viscosity average molecular weight is not an absolute value, but a relative molecular weight based on prior calibration with known molecular weights for the same polymer-solvent-temperature conditions. The parameter a depends on all three of these it is called the Mark-Houwink exponent, and tables of experimental values are available for different systems. 

A slightly different but useful way of defining the viscosity average molecular weight is the following ... 

Hven fractionated polymer samples are generally polydisperse, which means that the molecular weight determined from intrinsic viscosity experiments is an average value. The average obtained is the viscosity average as defined by Eqs. (1.20) and (2.40) as seen by the following argument ... 

MWR = is used, where Af is a melt-viscosity-average molecular weight defined by the equation Af = antilog, (0.493 log Tf + 3.5576, where Tj is... 

Table 3. Intrinsic Viscosity—Viscosity Average Molecular Weight Relationships as a Function of Hydrolysis...

For commercial purposes the molecular weight is usually characterised from measurements of the viscosity of dilute solutions. It has been shown that, for dilute solutions, the relation between the viscosity and the molecular weight (in this case the viscosity average molecular weight) may be given by the relationship... 

Viscosity average molecular weights Mv were determined using a Ubbelohde viscometer and diisobutylene solutions at 20 °C with at least three dilutions for every solution. The Mv was calculated from intrinsic viscosity28. Averages of two determinations are reported. Reproducibility was 10%. 

IV. Viscosity Average Molecular Weights of Polyisobutylenes 1. Introduction... 

Bearing in mind the conditions of the problem, we can assume that pressure drop per unit length is determined by viscosity, average velocity, as well as the depth and width of the micro-channel ... 

The viscosity average molecular weight of PGA was determined using the Mark-Hownik-Sakurade equation with the necessary constants from ref. [8]... 

The viscosity average molecular weight depends on the nature of the intrinsic viscosity-molecular weight relationship in each particular case, as represented by the exponent a of the empirical relationship (52), or (55). However, it is not very sensitive to the value of a over the range of concern. For polymers having the most probable distribution to be discussed in the next chapter, it may be shown, for example, that... 

My Number, weight, and viscosity average molecular weights, respectively. 

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