SIMSCI Polymer Reactors -- Kinetic Mechanisms

SIMSCI Polymer Reactors - Kinetic Mechanisms

Free Radical Polymerization

Free radical polymerization follows a general reaction mechanism scheme applicable to homopolymer or copolymer simulation. The homopolymer free radical polymerization mechanisms are a subset of the copolymer case . These mechanisms provide for free radical production through the thermal decomposition of up to three initiators, through the thermal decomposition of monomers, or via transfer reactions from previously generated free radicals.

Propagation reactions include the addition of monomer A (or monomers A and B) to live chains. The ultimate (final) monomer unit in the chain possesses an active radical center, generated from either monomer A or B. The supported termination reactions include: (a) the standard combination and disproportionation reaction mechanisms; (b) a termination mechanism involving a modifier or inhibitor. A complete set of transfer reactions involving transfer to initiator, monomer, solvent, modifier, or polymer is available. Refer to the tables in chapter 8 of the Polymer section of the PRO/II Add-On Modules Users’ Guide, version 5.11.

Coordination Complex Polymerization

Coordination complex polymerization follows a general reaction mechanism scheme applicable to homopolymer or copolymer simulation. The homopolymer free radical polymerization mechanisms are a subset of the copolymer case. These mechanisms provide for the thermal activation of a reaction site on a catalyst. Also supported are kinetic mechanisms for thermal decomposition reactions and transfer reactions involving monomer, solvent, and modifier.

Propagation reactions include the insertion of monomers A and B into live chains at the reaction site. Termination mechanisms also are supported. A complete set of transfer reactions involving transfer of catalyst, monomer, solvent, modifier, or polymer is available. Simply select the desired mechanisms from the lists in chapter 9 of the Polymer section of the PRO/II Add-On Modules Users’ Guide, version 5.11.

Stepwise Polymerization

Stepwise polymerization follows a general reaction mechanism scheme for Type I, II, and III polymerization systems. A discussion of this nomenclature is found in Chapter 10 of the Polymer section of the PRO/II Add-On Modules Users’ Guide. The mechanisms of the stepwise polymerization scheme describe reactions that occur between functional groups located on the monomer and growing polymer molecules. In the course of polymerization, these reaction steps may lead to the production of a small molecule condensate. The reaction mechanisms include: ring-opening and polyaddition reactions for use in Type I systems; the polycondensation I mechanism for use in Type II systems; and the polycondensation II mechanism for use in Type III systems. Refer to the tables in chapter 10 of the Polymer section of the of the PRO/II Add-On Modules Users’ Guide, version 5.11, for further details.

Model Kinetics

It is the set of kinetic mechanisms and chemical composition that ultimately determines the molecular structure and molecular weight distribution of the polymer. Each kinetic mechanism is described using the classic Arrenhius rate constant. This model requires a pre-exponential factor and the activation energy to be specified for each kinetic mechanism in the user-specified model.

In the free radical kinetics rate data, the effect of high operating pressure on the reaction rate constant also may be specified. Simply include a pressure coefficient and the reference pressure to be used in the Arrenhius rate expression.

In the stepwise kinetics data, the effect of acid concentration and equilibrium rate on the reaction rate constant also may be specified. Expressions for the rate constants are given in Chapter 10 of the Polymer section of the of the PRO/II Add-On Modules Users’ Guide, version 5.11.

Additional information

For additional information on the polymer reactor kinetic mechanisms and the use of PRO/II’s Polymer Reactors, refer to the Polymers section of the PRO/II Add-On Modules Users’ Guide, version 5.11.

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