Numerical modeling and experimental study of the frontal polymerization of the diglycidyl ether of bisphenol A/diethylenetriamine epoxy system

Frontal polymerization is a process in which a spatially localized reaction zone propagates through a monomer by converting it into a polymer. In particular, the heat produced during the curing process is exploited to promote the reaction of the monomer lying next to the propagating front, making this latter able to self-sustain. This approach represents an alternative solution to traditional polymerization methods and can be successfully applied to the preparation of many polymeric materials. In this study, frontal polymerization was numerically modeled to better understand it and to provide the basis for processing simulation. A finite-difference method was used to solve the thermal problem coupled with the equation describing the cure evolution for a reactor with a cylindrical geometry. The implicit backward time-centered space method was used. First, a one-dimensional model, able to describe the process in an adiabatic tube, was developed. The front ignition was simulated as if it were a hot surface warming one end of the reactor to trigger reactant polymerization. The model was able to predict the, formation of a reactive front advancing in the unreacted zone with a constant speed. The influence of the chemical and physical properties of the resin on process evolution was also investigated. By applying the alternate direction implicit method, a more detailed two-dimensional model able to describe a three-dimensional problem for a cylindrical reactor was also developed. With this model, it was possible to study the influence of boundary conditions on process evolution, considering a convective heat exchange with the environment through the reactor walls. Diglycidyl ether of bisphenol A, cured with diethylenetriamine (DETA), was used as the model system. Differential scanning calorimetry was used to produce a phenomenological model able to describe the cure process and to determine the physical properties of the resin. The validity of the approach was confirmed experimentally using a small cylindrical reactor. (c) 2005 Wiley Periodicals, Inc.