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

Photocuring of Epoxidized Cardanol for Biobased Composites with Microfibrillated Cellulose

“…The intensity of the peaks at 2927 cm −1 and 2854 cm −1 , and at 1600 cm −1 and 1583 cm −1 did not change; however, the peaks became slightly broader. The FT-IR spectra of the cured resins of this work were similar to those present in the literature [14].…”

“…The vibrations of the C=C aromatic bond were seen in the 1550–1650 cm −1 and 1400–1510 cm −1 regions [4,5,20]. A shoulder peak at 1258 cm −1 indicated the presence of the phenolic ether linkage [14,20]. The characteristic vibrations of the epoxide ring were found at 911 cm −1 [4,5,11,14,20], 860 cm −1 [4,12] and 776 cm −1 [4].…”

“…A shoulder peak at 1258 cm −1 indicated the presence of the phenolic ether linkage [14,20]. The characteristic vibrations of the epoxide ring were found at 911 cm −1 [4,5,11,14,20], 860 cm −1 [4,12] and 776 cm −1 [4]. Among these, the most suitable to be followed to assess the degree of curing of the EC was the 911 cm −1 signal of the epoxide group [14], as the signals at 860 and 776 cm −1 overlapped with peaks characteristic of the meta substituted (670–710, 750–805, 870–900 cm −1 ) and para substituted (845 cm −1 γCH) aromatic rings in the EC molecule [21,22,23], and with some photoinitiator’s signals (845 cm −1 and 780 cm −1 ).…”

“…Few studies though have been published on the photo-induced cationic polymerization of epoxidized cardanol derivatives, namely using electron beam and UV (254 nm) as radiation sources. Different epoxidized derivatives of cardanol, including also epoxide groups on the aliphatic chain, have been used in these works, where hexafluorophosphate and hexafluoroantimonate type cationic initiators were employed [12,13,14]. Photopolymerized epoxy cardanol showed however relatively weak mechanical properties, due to the low functionality of the monomers, leading to a low degree of crosslinking, and to the presence of the flexible aliphatic side chain.…”

“…The results obtained by photopolymerization are compared with those obtained for the thermal curing of an epoxidized cardanol with the same molecular structure [10]. Although the structures of the monomers and prepolymers used in previous works on photo-induced curing of epoxidized cardanol derivatives [12,13,14] are different from the one used here, some comparisons are possible and will be discussed. We hereby also confirm the possibility of preparing fully biobased photocured composites of epoxidized cardanol with microfibrillated cellulose, although a fairly high concentration of photoinitiator, of as much as 15 wt.%, was needed for leading the crosslinking reaction to completion.…”