Successful UV‐Induced RICFP of Epoxy‐Composites

Abstract

The UV‐curing of epoxy monomers by cationic photopolymerization is a powerful method for the production of polymer materials. The limit of film thickness in cationic photopolymerization of epoxy monomers has been recently overcome by introducing a novel radical induced cationic frontal polymerization (RICFP) system within this research group. The possibility to cure epoxides in bulk by UV‐light promoted here presents the novel approach to photocured composites. In the present work, the recently established RICFP system is applied on SiO2‐filled epoxy formulations based on bisphenol‐A diglycidyl ether. The influence of filler content on frontal propagation is examined in RICFP experiments. The composite materials are also investigated by dynamic mechanical thermal analysis to determine mechanical properties of the frontally polymerized products.

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.…”

Review on UV-Induced Cationic Frontal Polymerization of Epoxy Monomers

“…The frontal velocity decreased from 9 cm/min to 2.8 cm/min with increasing zirconia content from 0 to 80 phr [ 40 ]. Using the same formulation of BADGE and photo and thermal radical initiator, Klikovits et al [ 131 ], studied the effect of silica nanoparticles on frontal polymerization and mechanical properties of a BADGE-silica nanocomposite. Their studies showed that silica concentration of up to 3 phr can give a reproducible front, whereas 4 and 5 phr required a high-UV-intensity floodlight due to limited light penetration, in order to propagate the front.…”

Recent Advances in Cationic Photopolymerization

“…UV-cured bulk epoxy composites were successfully produced by Radical Induced Cationic Frontal Polymerization (RICFP); it was shown that the FP is started by the dissociation of a radical, thermal initiator (RTI) promoted by the heat released during surface UV-induced cationic ringopening polymerization. Subsequently, the carboncentered radicals are oxidized to carbocations by the presence of the iodonium salt in a RICP mechanism [3].…”