Monomer balance

Solution Assume that initiation occurs instantly as fresh monomer enters the reactor. A monomer balance for the CSTR gives... 

And the average value XiB of X B can be derived from the bubble-phase monomer-balance equation (7.100) as... 

If values of 6,m and K from Equation 5 are substituted into the monomer balance Equation 2, the values of Tmax as a function of pressure are obtained. Since eQ/RT 1 (T and Q always positive), it is possible to calculate, for each pair of values of 6,m and K, the minimum value of Ad/kaP below which a rate maximum is not possible. It may be seen from Table I that after passing through a maximum, (Ad/kaP)min approaches unity asymptotically with increasing K. 

To achieve proper monomer balance, the monomers were purified with great care. The stoichiometry needed to achieve the highest molecular weight polymer (Table I) required 1% excess of bistetracyclone. This suggests either that there were impurities in the bistetracyclone that... 

Severe polymerization conditions (350°C., 48 hours), in fact, gave lower molecular weight polymers ([yj] = 0.1) and a small amount of black, insoluble precipitate. These results suggest that there was considerable degradation which interfered with monomer balance. Such... 

Table I. Effect of Monomer Balance on Molecular Weight (Polymer XXb)...

Interval III is characterized by polymerization in a constant number of latex particles in the absence of monomer droplets. The concentration of monomer in the latex particles thus declines as polymerization progresses. The principal modification required for the application ofEq. (S) in modeling Interval III is its coupling with a monomer balance equation and the modification of the growth factor K to incorporate the declining monomer concentration. A full monomer balance equation for a batch reactor demands the consideration of the monomer consumed in both the aqueous phase and the particles iMin and Ray, 1974). Frequently, however, the aqueous phase consumption is relatively small so that only consumption in the latex phase is significant. The latter is given by... 

Other materials balance equations may be coupled with Eq. (5) in an way analogous to the monomer balance equation. This is necessary if the availability of some species changes significantly with time, e.g., when the initiator has a half-life comparable to (or shorter than) the polymerization half-life. 

Vitrac H., Hauville C., Collin F., Couturier M., Therond P., Delaforge M., Remita S., Jore D., Gardes-Albert M., Hydroperoxide characterisation as a signature of the micelle/monomer balance in radiation-induced peroxidation of arachidonate. Free Radical Research, 2005,39,519-528. 

Precise control of Initial monomer balance with many polyamide systems can be accomplished by measuring the pH of an aqueous solution of the diamine and diacid. With reaction systems not amenable to this type of measurement, very precise metering techniques for monomer addition must be used. 

Table 9. Monomer Balance and Properties of Fibers from MePPD-TA...

A well-mixed CSTR is a good approximation for most of the continuous reactors used in the production of polyolefins. Therefore, the monomer balance under steady-state conditions is... 

As an example, apply Equation 3.96 to a monomer balance for a steady-state overflow CSTR. Equation 3.96 becomes... 

Polymerization can occur under non-equilibrium conditions, thus eliminating the critical dependency on the monomer balance (typical of high-... 

Taking a steady-state monomer balance around the CSTR, we have... 

Volume contraction due to the difference in polymer and monomer densities can be as high as 20% for bulk polymerization, and should not be neglected when solving the material balances. Solution of the initiator balance and substitution into the monomer balance lead to a differential equation for conversion, Eq. (91), where the volume contraction factor is deflned as s = pjinai Pa) /Pfind where is the... 

Substitution of these expressions into the monomer balance leads to a nonlinear relationship between conversion and 0 [Eq. (95)]. 

Integration of Equations 16.26-16.29 along with the monomer balance will describe the monomer conversion and molecular weight distribution as a function of time for the batch anionic polymerization. Addition of the enthalpy balance will allow the simulation to be done nonisothermally. 

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