Numerical study on frontal polymerization subjected to buoyancy-induced convection: Front acceleration and instability

Frontal polymerization has been demonstrated to be a rapid, energy-efficient manufacturing method for thermoset polymers and composites, which involves a self-propagating exothermic reaction front. Fluid convection can affect the reaction–diffusion dynamics of the polymerization front and lead to thermo-chemical instability, enabling spontaneous pattern formation in the polymer product. In the present work, we utilize reaction–diffusion–convection modeling to report how the buoyancy-driven convection in frontal polymerization can increase the velocity of the front through a reaction–diffusion–convection process under typical processing conditions. The reaction–diffusion–convection model provides insight into the underlying physics and describes how convective heat transfer affects the local heat exchange and promotes the chemical reaction rates. The limit of the front acceleration regime is also explored under super-gravity conditions, where the heat dissipation limits the front velocity and quenches the polymerization. With various orientations of the frontal polymerization front with respect to gravity, the magnitude and vorticity of the buoyancy flow vary, generating different effects on the velocity, shape, and instability of the propagation front.