Cumulative molecular weights

Figure 1 Is a flow sheet showing some significant aspects of the Iterative analysis. The first step In the program Is to Input data for about 50 physical, chemical and kinetic properties of the reactants. Each loop of this analysis Is conducted at a specified solution temperature T K. Some of the variables computed In each loop are the monomer conversion, polymer concentration, monomer and polymer volume fractions, effective polymer molecular weight, cumulative number average molecular weight, cumulative weight average molecular weight, solution viscosity, polymerization rate, ratio of polymerization rates between the current and previous steps, the total pressure and the partial pressures of the monomer, the solvent, and the nitrogen.

Health and Safety Factors. Like other low molecular weight ketones, MIBK is an anesthetic chemical with no highly cumulative toxicological effects. Inhalation of vapors can irritate mucous membranes. 

It should he understood that the weight average molecular weights appearing in equation (IT) are cumulative ones. 

Another sampling effect which deserves mention is that since the molecular weight distribution shifl towards higher molecular weights with conversion, a slice will not in general contain proportionate amounts of polymer from all conversions. This dufting can be accounted for in the theoretical predictions by incorporating it into cumulation of the instantaneous property distributions (e.g. Equation 8). 

Figure 4. Typical computer-generated plot of weight differential and cumulative distributions of molecular weight...

The second new program allows the user to compare the shapes of molecular weight distributions. For example, if we have the cumulative distribution of hydrodynamic volume for two polymers we can plot the hydrodynamic volume corresponding to the 10th percentile of the distribution for polymer A against the similarly defined hydrodynamic volume for polymer B. Such a plot, made for the entire distribution of both polymers, is called a "quantile... 

Fig Typical cumulative molecular-weight distribution curve for a sample of polypropylene gradient-elution data (O) and data from gel permeation chromatography. 

Fig. 15.4 (a) Cumulative molecular weight distributions of compounds in the Gasteiger [33] and... 

The differences can also be seen in Figure 15.4, which compares cumulative distributions of these properties between the Gasteiger and Roche datasets. Many of the literature compounds are very simple, with low molecular weight, few polar atoms, and few functional groups. They have often been included in solubility datasets because they are well characterized and because accurate solubility data are available for them, rather than because they are druglike. The inclusion of many such simple compounds in a training set for a solubility prediction tool may focus the tool on an area of chemistry space that is not well populated with druglike molecules and may make the tool less useful for the prediction of the solubility... 

The first moment of the distribution is Pt0T the total, cumulative molar concentration of polymeric material. As the molecular weight of polymeric species increases, branching and crosslinking reactions yield a thermoset resin. Chromatography analysis of epoxy resin extracts confirms the expected population density distribution described by Equation 4, as is shown in Figure 2. Formulations and cure cycles appear in Table II. 

Suppose a polydisperse system is investigated experimentally by measuring the number of particles in a set of different classes of diameter or molecular weight. Suppose further that these data are believed to follow a normal distribution function. To test this hypothesis rigorously, the chi-squared test from statistics should be applied. A simple graphical examination of the hypothesis can be conducted by plotting the cumulative distribution data on probability paper as a rapid, preliminary way to evaluate whether the data conform to the requirements of the normal distribution. 

Table I. Cumulative Molecular Weight Distribution by Gel-Permeation Chromatography...

FJg. 2. Cumulative and differential molecular weight distribution for polystyrene from mutual radiation... 

Again, in equations 8 and 9, D is the cumulative dose and the superscript o reflects the original molecular weights of the unexposed sample (15, 16). 

Weight Fraction Differential Cumulative Molecular Weight Light Cumulative Lansing- Kraemer... 

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