Light fast epoxy resins

Poor light fastness (exterior durability) of BPA type epoxy resins, due to the presence of aromatic ether linkages, limits their outdoor applications. Epoxy resins with improved weathering performance can be obtained by using aliphatic epoxy resins. One of the important epoxy resins in this class is the glycidyl ether of hydrogenated bisphenol A. These resins have lower viscosity, lower reactivity and higher cost compared to BPA epoxy resins. 

Other types of aliphatic epoxy resins with glycidyl functionality are derived by copolymerization of glycidyl methacrylate with other acrylate monomers. A range of products is offered by varying the glycidyl methacrylate content, co-monomer composition and MW. These resins produce coatings with excellent exterior durability and acid etch resistance. They are reported to be widely used in 

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Crivello and Lam have demonstrated the use of diaryliodonium salts as photoinitiators for polymerization of electron-rich olefins, cyclic ethers, cyclic sulfides, lactones and spiro orthoesters, but a vast majority of their published work concerns polymerization of substituted oxiranes, illustrating the potential of such systems in photocuring of epoxy resins. Such polymerizations can be quite fast in the most favorable example, a 93% yield of polymer of Mn 10,700 was obtained from 3-vinylcyclohexene oxide after only 90 seconds of irradiation at room temperature with 4,4 -di-tert-butyldiphenyliodonium hexafluoroantimonate as initiator (3). The substituted salts are often preferred to the simple unsubstituted diphenyliodonium compounds for reasons of solubility (2). The use of diaryliodonium salts in combination with various dyes allows one to initiate cationic polymerization with visible light (5). 

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