Photopolymerization of Bio-Based Epoxy Prepolymers Derived from Cashew Nut Shell Liquid (CNSL)

Cashew nut shell liquid (CNSL) is a non-food natural polyphenol that is a renewable resource. In the present work, we prepared cardanol- and CNSL-based epoxy polymers by photopolymerization using various cationic photoinitiators and photosensitizers. Epoxy prepolymers were used as a precursor and prepared by thermal treatment of epoxy cardanol and epoxy CNSL according to previous work. Photopolymerization of these prepolymers with bis (4-tert-butylphenyl) iodonium hexafluorophosphate (BIP) proceeded more quickly than that of other photoinitiators. We obtained UV-cured epoxy prepolymers with high gel content by 20 seconds of UV irradiation. These UV-cured CNSL prepolymers were thermally stable up to 250-300 degrees C, indicating that these can be used as heat-resistant materials. The photopolymerization of epoxy prepolymers was analysed by NMR and FT-IR and characterized by drying properties, hardness, thermal and mechanical properties.