UV Cure of Epoxysiloxanes and Epoxysilicones

The discovery and development of onium salt cationic photoinitiators

“…Every onium-salt photoinitiator examined was poorly soluble in the epoxy functional silicone resins. The problem was solved neatly by Eckberg and LaRochelle, 67,68 who prepared bis(4-dodecylphenyl)-iodonium hexafluoroantimonate (XX) using the reaction of dodecylbenzene with KIO 3 in sulfuric acid followed by metathesis with NaSbF 6 (eq 19):…”

Radiation Curing — A Personal Perspective

“…Exceptionally rapid curing epoxy-functional silicones have also been reported recently. 9,18 Vinyl ether-functional resins are becoming more available for both UV and EB cationically curable compositions and are the subject of Chapter 6. In general, cure rates are substantially faster for vinyl ethers than epoxies; commercially significant EB curable epoxies have not been reported.…”

“…44 Recently, long-chain substituted diaryliodonium salts, such as bis(4-dodecylphenyl)iodonium 3 and 4-octyloxyphenyl, phenyliodonium 4 hexafluoroantimonates (Ar = 1,4-disubstituted benzene and the anion is not indicated), have been reported specifically for epoxy-functional silicone release coatings. 9 ,18 In addition to enhancing solubility in the silicone formulations, these substituted iodonium salts are essentially nontoxic,45 in contrast to diphenyliodonium salts, which had been removed from the marketplace owing to toxicity. The spectral response of triarylsulfonium and diaryliodonium salts can be extended to longer wavelengths by photosensitization.…”

“…200°C were determined for epoxy silicones, cured by photoinitiated cationic polymerization under ambient conditions. 9 The authors noted that the high Tg values might reflect thermal cure occurring during the DSC determinations. Tg values as high as ca.…”

UV-Radiation Curing of Adhesives

“…41 The introduction of a dimethyl-siloxane group between two cycloaliphatic epoxy groups was found to increase drastically the reactivity of these monomers. 59,134 The cyclo epoxy group can be located at the ends of the polydimethylsiloxane chain and/or on pendent groups. 135 Such UV-cured polymers can work as release coatings because the low surface energy of the polydimethylsiloxane chains predominates at the coatings interface with a PSA.…”