Cationic Frontal Polymerization

Photocuring of epoxy resins by common techniques is limited to very thin layers (like in coatings or printing inks) due to the little penetration depth of the UV-light. Therefore the combination of frontal polymerization and radical induced cationic polymerization leads to a superior method of epoxy photocuring. With radical induced cationic frontal polymerization (RICFP) the bulk curing even of complex shapes is possible. The initiation can be done by locally application of either UV-light or also heat.

The usage of C-C labile compounds like benzopinacol enabled us to also cure the industrial most used epoxy resin: bisphenol-A-diglycidylether (BADGE) [1]. By using a newly developed Al-based cationic photoinitiator the frontal polymerization of layers thinner than 1 mm is possible. Surprisingly it is also possible to start the cationic frontal polymerization under water.

Epoxyresins are also frequently used in composite technology. Up to 50 Vol% of fillers like carbon fibres are possible [3, 4]. The following two videos show a dual curing system for prepreg technology and a carbon fibre composite.