Effect of Reaction Path and Initial Distribution on Molecular Weight Distribution of Irreversible Condensation Polymers

Abstract

Our results point to the weakness in assuming, as is usually done, that the maximum value of PDI for condensation reactions in a well-mixed batch reactor is 2. Thus, if a polymerization reaction is controlled by monitoring the number average molecular weight, the resulting =, can be widely different, depending on whether R was slightly below or above 1. A group attached to a polymer is so low that it is less than the product of the probability 7 of reaction of an A group attached to a polymer and the probability ( I -a) of finding an unreacted B group. Hence, the weight fraction of the species of the type (BBAA), is lower than the weight fraction of the species of the type (BBAA),BB. Thus, the weight fraction of any species containing an even number of units is less than the weight fraction of the next larger species containing one more unit, even when n is large. This disparity in the weight fractions is so large that two separate curves, one each for molecules containing even and odd number of units, may be drawn as done in Effectiveness Factors and Mass Transfer in Trickle-Bed ReactorsRates of hydrogenation of a-methyl styrene were measured at 40.6OC and 1 atm in a recycle, trickle-bed reactor using a palladium/aluminum oxide catalyst. Data for different hydrogen concentrations in the gas and liquid feed streams suggested that except, at high liquid flow rates, on part of the outer surface of the catalyst the mass transfer limitation was very small, indicating a gas covered type of surface. A procedure was developed for evaluating effectiveness factors for the nonuniform boundary conditions existing when part of the particle surface is covered by gas.

Polymerization Reaction Engineering

“…The reduction in the number of equations provides simplification for subsequent solutions by analytical methods, including the use of continous transforms and numerical techniques. An objection to this technique (35) is that short chains, which lead to the greatest inaccuracies, are the most numerous at all times during a condensation polymerization. tions, however, the equations cannot be linearized.…”

High-Performance Fibers

“…Contrary to standard melt polymerization the reaction using diamines and diacid chlorides is irreversible. General theoretical considerations for these type reactions are given in [13] and kinetics for the aramids polymerization process is described in [14]. The reaction is divided into two phases: A free amine phase (less than 50% conversion, Eq.…”

General matrix formula for the weight-average molecular weights of crosslinked polymer systems

“…As clarified by Stockmayer, 2 this reaction system yields the same molecular constitution as an equilibrium system if it is conducted in a batch reactor. With the use of reactor operations other than batch polymerization, including semibatch operations, continuous stirred-tank re-actor, and tubular reactors with a recycle loop, the molecular constitution deviates from an equilibrium combination of molecules 24,25 (i.e., the probability of reaction and how each molecule is combined (the connection rule) are not the same for all A f monomers). To illustrate the nonequilibrium effects, we consider the intermediate monomer feed method.…”