The effect of reactor geometry on frontal polymerization spin modes

Abstract

Using reactors of different sizes and geometries the dynamics of the frontal polymerization of 1,6-hexanediol diacrylate (HDDA) and pentaerythritol tetraacrylate (PETAC), with ammonium persulfate as the initiator were studied. For this system, the frontal polymerization exhibits complex behavior that depends on the ratio of the monomers. For a particular range of monomers concentration, the polymerization front becomes nonplanar, and spin modes appear. By varying the reactor diameter, we experimentally confirmed the expected shift of the system to a greater number of "hot spots" for larger diameters. For square test tubes a "zig-zag" mode was observed for the first time in frontal polymerization. We confirmed the viscosity-dependence of the spin mode instabilities. We also observed novel modes in cylinder-inside-cylinder reactors. Lastly, using a conical reactor with a continuously varying diameter, we observed what may be evidence for bistability depending on the direction of propagation. We discuss these finding in terms of the standard linear stability analysis for propagating fronts. (c) 2002 American Institute of Physics.

Frontal Polymerization

“…Masere et al [101] found that silica gel significantly altered the spin behavior, as predicted by Garbey et al [77]. Pojman et al made a similar observation in square reactors [103]. Pojman et al studied the dependence of spin modes on viscosity with the FP of HDDA with persulfate initiator [106].…”

“…Pojman et al observed zigzag modes in square reactors [103] and bistability in conical reactors [104].…”

Historical perspective and contribution of US researchers into the field of self-propagating high-temperature synthesis (SHS)/combustion synthesis (CS): Personal reflections

“…Professor Volpert published several papers with Professor Matkowsky on the theory of gasless and various aspects of filtration combustion in porous structures with and without deformation. He also contributed to better understanding of combustion in microgravity environments and mathematical modeling of frontal polymerization and understanding of wave propagation during free-radical polymerization with the gel effect [53][54][55][56][57][58][59][60][61][62][63].…”

Thermal frontal polymerization with a thermally released redox catalyst

“…Such nonplanar modes of propagation have been the subject of much investigation. 40,[45][46][47][48][49][50][51] The complexity of the front increases with the value of the effective energy of activation. By reducing the number of propagating radicals, the transition metal reduces the contribution of the energy of activation for the termination step, which increases the effective activation energy.…”