Phenomenological model for the reaction order n in the kinetics of curing an elastomer EPDM
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.428
Phenomenological model for the reaction order n in the kinetics of curing an elastomer EPDM S. Gómez-Jimenez.1, A.M. Becerra-Ferreiro.1, E. Jareño-Betancourt.1, J. Vázquez-Penagos.2, 1 Universidad Autónoma de Zacatecas, Unidad Académica de Ingeniería, Av. López Velarde 801, Zacatecas, Zac., México.
2
Elastomer Solutions México S de R. L. de C. V., Circuito Fresnillo Poniente 21 s/n, Parque industrial Fresnillo, Zacatecas, México.
Abstract: The precise control of curing reaction parameters allows a better crosslinking polymer. Modelling and optimization of this process require a correct kinetic of curing model. The kinetics of the crosslinking reaction is studied for the ethylene propylene diene monomer (EPDM) synthetic elastomer by mobile die rheometer (MDR). The kinetic parameters of reaction were calculated from Kamal-Ryan, Sestak-Berggren, and the Isayev-Deng methods at different temperatures. An Arrhenius-type function for the order of reaction n is introduced to improve the adjusting. Finally, a graphical and analytical description of the cure kinetics was developed. The order of reaction is predicted to better establishment of processing time. It was noted that for EPDM at higher temperatures, the increase of the rate of reaction occurs in short period of time, which could cause premature curing if the supply system is inadequate.
INTRODUCTION: Vulcanization is one of the essential processes in the rubber industry, involves an enormous amount of energy to convert a material without form into an elastic finished product [1]. Elastomers consist of independent high molecular weight molecules when they are in the monomer or non-vulcanized states. The cross-links between these molecules show nonlinear viscoelastic behavior allowing the flow and processing by injection. During the injection, a chemical reaction of vulcanization (or curing) takes place. The vulcanizing process presents three stages: induction, curing, and post-curing. [2]. The rubber curing is an exothermic process of high complexity in which several reactions coincide. The vulcanization mechanism and the rate of reaction depend on the structure of the rubber, the concentration of activators and accelerators as well as the diffusivity, and thermodynamics of each reaction. The curing rate increases with
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temperature and therefore a finite time for filling the mold is needed [3, 4]. The final properties of the formed polymer depend largely on reactions that occur during vulcanization, so it is necessary to study the curing kinetics of the compound to determine the time and degree of curing [5]. On the other hand, the kinetics associated with a chemical process is not correctly characterized by the so-called kinetic triplet; that is activatio
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