Highly reactive photothermal initiating system based on sulfonium salts for the photoinduced thermal frontal cationic polymerization of epoxides: a way to create carbon-fiber reinforced polymers

Abstract

Photoinduced thermal frontal polymerization of epoxides made possible by use of a dual-cure initiating system based on sulfonium salts.

Photoinitiating systems and kinetics of frontal photopolymerization processes – the prospects for efficient preparation of composites and thick 3D structures

“…Polymer Chemistry opaque and thick samples. 109 To obtain these conditions, the hybrid systems of photo and thermal initiators were investigated. After short irradiation of the point of a sample's surface, the photoinitiator decomposes with the release of super acid that initiates the polymerisation process in these systems.…”

“…111 However, the pyrylium salt is chemically unstable, leading to relatively poor pot-life. 109 Therefore, a need arose for a better solution. Gachet et al proposed a photo/thermal initiating system based on sulfonium salts.…”

“…Gachet et al proposed a photo/thermal initiating system based on sulfonium salts. 109 Triarylsulfonium salts were described above as one of the more efficient types of onium salts (Fig 15), but they do not exhibit any particular thermal activity, making them thermally stable. On the other hand, the exchange of one or two aryl rings with benzyl or alkyl substituents lowers this stability, which makes these salts efficient thermal initiators of epoxy monomers.…”

“…15) provides an efficient initiating system of epoxy resin cationic frontal photopolymerisation where the photoactive one initiates the polymerisation process on the surface of the sample and generates the heat necessary to decomposed thermally active one and curing the sample throughout its depth. 109 In the system proposed by Gachet et al, 1 wt% of TAS was sufficient to generate a front of 250°C. At this concentration of TAS, three PDAS were tested with CADE monomer.…”

“…One of them is severely decreasing the temperature jump in resins with a high concentration of fillers. 109 Another is utilising a thermally stable photoinitiator in full sample volume, despite being used only on the sample surface to initiate a front.…”