Temperature average molecular

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. 

T is the glass-transition temperature at infinite molecular weight and is the number average molecular weight. The value of k for poly(methyl methacrylate) is about 2 x 10 the value for acrylate polymers is approximately the same (9). A detailed discussion on the effect of molecular weight on the properties of a polymer may be found in Reference 17. 

These values are given for polymers of narrow molecular-weight distribution, with number-average molecular weights (M ) of about 20,000 prior to chlorination. Chlorination reactions are carried out under homogeneous conditions in CCl solutions at temperatures between 90 and 110°C with viscosities at about 5 Pa (50 P). 

If critical pressure and critical temperature are given in Pa and K, respectively, viscosities in centipoise result. The variable Io is either the low pressure pure component or mixture viscosity according to whether a pure component or mixture is being considered. For mixtures, simple molar average pseiidocritical temperature (Kay s rule), pressure, and density, and molar average molecular weight are used. The vapor density can be predicted by the methods previously discussed. Errors of above 5 percent are common for hydrocarbons and their mixtures. Experimental densities will reduce the errors slightly. 

The viscous shear properties at any given shear rate are primarily determined by two factors, the free volume within the molten polymer mass and the amount of entanglement between the molecules. An increase in the former decreases the viscosity whilst an increase in the latter, i.e. the entanglement, increases viscosity. The effects of temperature, pressure, average molecular weight, branching and so on can largely be explained in the these terms. 

The products of the process have a density of about 0.96 g/cm, similar to the Phillips polymers. Another similarity between the processes is the marked effect of temperature on average molecular weight. The process is worked by the Furukawa Company of Japan and the product marketed as Staflen. 

It has been observed that in the polymerisaton of methyl methacrylate there is an acceleration in the rate of conversion after about 20% of the monomer has been converted. The average molecular weight of the polymer also increases during polymerisation. It has been shown that these results are obtained even under conditions where there is a negligible rise in the temperature (<1°C) of the reaction mixture. 

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