UV‐ignited frontal polymerization of an epoxy resin

Abstract

By combining frontal polymerization and radical‐induced cationic polymerization, it was possible to cure thick samples of an epoxy monomer bleached by UV light. The effect of the relative amounts of cationic photoinitiator and radical initiator was thoroughly investigated and was related to the front's velocity and its maximum temperature. The materials obtained were characterized by quantitative conversion also in the deeper layers, not reached by UV light. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2066–2072, 2004

Successful UV‐Induced RICFP of Epoxy‐Composites

“…The reaction mechanism of RICFP for epoxy resins was first described by Mariani et al [15] and following deeply investigated by Bomze et al [16] It was shown that the FP is started by the dissociation of a radical thermal initiator (RTI) promoted by the heat released during surface UVinduced cationic ring-opening polymerization. Subsequently, the carbon-centered radicals are oxidized to carbocations by the presence of the iodonium salt PAG (On + in Figure 1) in a RICP mechanism.…”

Thermal frontal polymerization with a thermally released redox catalyst

“…18 Although most studies have focused on free-radical chemistry, other reaction mechanisms can be used, including urethane formation, 26 ring-opening metathesis polymerization, 27 and frontal epoxy curing. [28][29][30][31] A significant challenge for free-radical frontal polymerization is how to achieve a long pot life and a low front temperature. If we rely on the Arrhenius kinetics of the initiator decomposition, we must trade off pot life for front temperature, that is, a longer pot life means that the front temperature must be allowed to reach a higher value.…”

Dual-cure Photo-thermal Initiating System for Cationic Polymerization of Epoxy under LED Visible Light

“…As example, the decrease of light penetration with increasing thickness represents a serious drawback for thick, pigmented coatings and fiber-reinforced composites. Therefore, the concept of dual-cure initiating systems based on both photo-thermal curing appears as a promising alternative to solve the issue [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Indeed, the combination of a photochemical polymerization promoting a thermal curing has rendered possible the curing of thick samples.…”

“…Moreover, the thermal process can also be used to complete the curing of the epoxide resin in shadowed areas, typically in the case of 3D parts. In the best cases, the photochemical process would also speed up the thermal curing to perform a photoinduced thermal frontal polymerization [1][2][3][4][5][6][7][8][9][10][11][12][13][14].…”