Radical induced cationic frontal polymerization as a versatile tool for epoxy curing and composite production

Abstract

Radical induced cationic frontal polymerization (RICFP) is an extremely powerful and elegant alternative curing technique that allows cationic bulk curing of epoxy resins with very little energy consumption, as well as curing in compartments that are not readily accessible. We recently introduced a bisphenol‐A diglycidylether (BADGE) based system that allows the bubble‐free photocuring of this widely used epoxy resin. In this article, we describe the high storage stability and possibilities to influence the curing speed via the initiator concentrations of different formulations. These properties allow the adjustment of the frontal polymerization to ones need. We also show that the (thermo)mechanical and electrical properties of frontal cured epoxy polymers compares favorably with those of state of the art material. Finally, different strategies to overcome the challenges on producing epoxy resin based mica composites via RICFP are presented. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3751–3759

Photoinduced cationic frontal polymerization of epoxy–carbon fibre composites

“…It was demonstrated in previous reportes that FP is started by the dissociation of a radical thermal initiator promoted by the heat released during surface UV‐initiated cationic ring‐opening polymerization. Subsequently, the carbon‐centred radicals are oxidized to carbocations by the presence of the iodonium salt through a radical‐induced cationic mechanism.…”

“…Crivello also reported radical‐induced cationic FP (RICFP) to realize UV crosslinking through the thickness of a photocurable formulation. In a more recent paper, we reported the possibility of curing bulk pristine epoxy formulations containing SiO 2 by RICFP; the influence of the filler content on frontal propagation was investigated, showing a decrease of front velocity and front starting time with increasing filler content . We have also reported the UV‐crosslinking preparation of epoxy–glass fibre composites via RICFP.…”

Successful UV‐Induced RICFP of Epoxy‐Composites

“…The particles with high surface and small particle size were chosen to show the change in polymerization behavior and product features in a homogenous dispersion. As reported, [17] the filler was expected to show two effects on the RICFP: (a) the decrease of penetration depth due to the scattering of light at the particle surface and (b) the decrease of heat dissipation in the formulation due to the insulating properties of SiO 2 . The first of these effects was expected to be the limiting factor for a succeeding initiation of RICFP experiments using fillers, as it is necessary to initiate the light-induced reaction in a certain volume of the formulation to generate enough heat in order to activate the RTI.…”

“…The formulations for the RICFP of composite materials were prepared according to Bomze et al [17] 2 mol% IOC-8 SbF 6 and 2 mol% TPED were dissolved in the smallest possible amount of dichloromethane. The weighed amount of SiO 2 nanopowder was added to the solution.…”

Synthesis of crosslinked PEG/IL blend membrane via one‐pot thiol–ene/epoxy chemistry

“…Epoxy resins, or called polyepoxides, are a class of polymers formed by monomers or oligomers containing epoxy groups, usually with the presence of crosslinkers, such as amines. The excellent chemical and thermal resistance, good mechanical properties, and notable adhesion of epoxy resins allow them to play important roles in various industrial applications, such as coating, reinforcement, and adhesives . Recently, several groups have expanded these materials to gas separation, especially as CO 2 separation membranes, thanks to the facile and rapid crosslinking, tunable chemical structure and the presence of secondary amines .…”