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Numerical modeling of self-propagating polymerization fronts: The role of kinetics on front stability (1997)

Solovyov, Stanislav E. ; Ilyashenko, Victor M. ; Pojman, John A.

Woodbury, NY : American Institute of Physics (AIP)

Chaos 7 (1997), S. 331-340

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ISSN: 1089-7682

Source: AIP Digital Archive

Topics: Physics

Notes: Frontal propagation of a highly exothermic polymerization reaction in a liquid is studied with the goal of developing a mathematical model of the process. As a model case we consider monomers such as methacrylic acid and n-butyl acrylate with peroxide initiators, although the model is not limited to these reactants and can be applied to any system with the similar basic polymerization mechanism. A three-step reaction mechanism, including initiation, propagation and termination steps, as well as a more simple one-step mechanism, were considered. For the one-step mechanism the loss of stability of propagating front was observed as a sequence of period doubling bifurcations of the front velocity. It was shown that the one-step model cannot account for less than 100% conversion and product inhomogeneities as a result of front instability, therefore the three-step mechanism was exploited. The phenomenon of superadiabatic combustion temperature was observed beyond the Hopf bifurcation point for both kinetic schemes and supported by the experimental measurements. One- and two-dimensional numerical simulations were performed to observe various planar and nonplanar periodic modes, and the results for different kinetic schemes were compared. It was found that stability of the frontal mode for a one-step reaction mechanism does not differ for 1-D and 2-D cases. For the three-step reaction mechanism 2-D solutions turned out to be more stable with respect to the appearance of nonplanar periodic modes than corresponding 1-D solutions. Higher Zeldovich numbers (i.e., higher effective activation energies or lower initial temperatures) are necessary for the existence of planar and nonplanar periodic modes in the 2-D reactor with walls than in the 1-D case. © 1997 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.166248

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Theoretical aspects of self-propagating reaction fronts in condensed medium (1995)

Ilyashenko, Victor M. ; Solovyov, Stanislav E. ; Pojman, John A.

Hoboken, NJ : Wiley-Blackwell

AIChE Journal 41 (1995), S. 2631-2636

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ISSN: 0001-1541

Keywords: Chemistry ; Chemical Engineering

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology

Notes: Exothermic chemical reactions are capable otautocatalytic self-propagation in a condensed reactive medium as a thermal wave. These take place in self-propagating high-temperature synthesis, frontal polymerization, curing of epoxy resins, and various solid-phase reaction processes. The lack of accurate analytical solutions for the front velocity and spatial parameter distributions has led to a period of approximate analytical solutions based on the infinitely narrow reaction zone assumption. A more accurate reaction zone approximation is presented that results in new equations for temperature and concentration spatial distributions as well as the wave velocity. Necessaty conditions for nondegeneration of the combustion wave were also obtained.

Additional Material: 6 Ill.