Abstract
Epoxy resins are among the most important building blocks for fabrication of thermosets for many different applications thanks to their superior thermo-mechanical properties and chemical resistance. The recent concerns on the environmental problems and the progressive depletion of petroleum feedstocks have drawn the research interest in finding biobased alternatives. Many curing techniques can be used to obtain the final crosslinked thermoset networks. The UV-curing technology can be considered the most environmentally friendly because of the absence of volatile organic compound (VOC) emissions and mild curing conditions. This review provides an overview of the state of the art of bio-based cationic UV-curable epoxy resins. Particular focus has been given to the sources of the bio-based epoxy monomers and the applications of the obtained products.
Highlights
The aliphatic structure of the epoxidized vegetable oils (EVOs) leads to thermosets with low thermo-mechanical properties; this limits their usage alone in non-structural applications. They have been mostly used as matrices for bio-composites with cellulose [9] or as tougheners in blends with petroleum-derived epoxy resins since their flexible nature can enhance the fracture and impact properties of the thermoset materials [10,11,12]
The obtained cross-linked networks are potentially biodegradable through the cleavage of the glycerol ester bonds [2,13]. Another renewable monomer source is the cashew nut shell liquid (CNSL), which resides in the Anacardium occidentalis mesocarp
Crivello discovered that diaryliodonium salts (Ar2 I+ MtXn− ) could generate high acidic solutions when irradiated by UV light
Summary
Among bio-based monomers, vegetable oils are an interesting renewable resource since they are cheap and abundant They are composed of 90–95% triglycerides with a high number of double bonds. The aliphatic structure of the epoxidized vegetable oils (EVOs) leads to thermosets with low thermo-mechanical properties; this limits their usage alone in non-structural applications They have been mostly used as matrices for bio-composites with cellulose [9] or as tougheners in blends with petroleum-derived epoxy resins since their flexible nature can enhance the fracture and impact properties of the thermoset materials [10,11,12]. The obtained cross-linked networks are potentially biodegradable through the cleavage of the glycerol ester bonds [2,13] Another renewable monomer source is the cashew nut shell liquid (CNSL), which resides in the Anacardium occidentalis mesocarp.
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