Photocuring of epoxidized cardanol with microfibrillated cellulose for biobased composites

Recently, due to environmental concerns, the interest for biobased materials, and for sustainable processes, is steadily increasing. Cardanol is an alkylphenolic compound derived from Cashew NutShell Liquid (CNSL), an annually renewable, non-food, sustainable raw material extracted from cashew nutshells. Epoxidized cardanol is commercially available and can be thermally cured, obtaining interesting mechanical and thermal properties [1]. Photopolymerization is considered a green technology owing to low energy requirements, room temperature operation, and absence of solvents. Its use for the curing of biobased monomers and prepolymers is therefore of interest [2]. Recently the possibility of photocuring CSNL derived epoxy prepolymers with UVC light (254 nm) has been explored, obtaining polymers with high gel content and thermally stable up to 250 – 300 °C [3]. In this work the photocuring of a commercial epoxidized cardanol, with a cationic photoinitiator, is reported. Photocured biobased composites were also prepared: microfibrillated cellulose (MFC) wet templates were prepared by filtration, and then impregnated with the epoxidized cardanol, after replacing water with acetone via solvent exchange route. Then the impregnated mats were then irradiated with UVA light (> 320 nm). Fourier Transform InfraRed (FTIR) spectroscopy was used to investigate the extent and the kinetics of the photocuring, both for the pure epoxidized cardanol and for the composites, observing the disappearance of the 910 cm-1 peak related to the epoxy ring. The thermomechanical properties were assessed by thermogravimetric analysis, differential scanning calorimetry and dynamic mechanical analysis.