LAUSR

Abstract Sorbitol polyglycidyl ether (SPE), which is a bio-based water-soluble epoxy resin, was cured with lysine (Lys) and arginine (Arg) as basic amino acids and with cysteine (Cys) as an acidic amino acid. Furthermore, biocomposites of the Lys- and Arg-cured SPE (SPE-Lys and SPE-Arg) and Cys-cured SPE (SPE-Cys) with chitin nanofiber (ChNF) not higher than 10 wt% were successfully prepared by compression molding and casting methods, respectively. Also, SPE-Cys biocomposites with chitosan nanofiber (CsNF) not higher than 2 wt% were successfully prepared by the casting method. The FT-IR spectral analysis of the cured resins suggested that the e-amino and carboxy groups of Lys, α-amino and carboxy groups of Arg, thiol group of Cys mainly reacted with epoxy groups of SPE. The FT-IR spectral analysis of the ChNF biocomposites suggested that a side reaction of SPE with acetic acid which was contained in ChNF suspension occurred. The dynamic mechanical analysis revealed that a higher order of the loss modulus peak temperature (Tα) was SPE-Lys (39 °C) > SPE-Arg (33 °C) > SPE-Cys (21 °C). Although Tαs of ChNF biocomposites were lower than those of the corresponding cured resins, Tαs of SPE-Cys/CsNF biocomposites were higher than that of SPE-Cys by the action of CsNF as a basic catalyst. The storage moduli over the range of 50–100 °C for SPE-Lys/ChNF, SPE-Cys/ChNF and SPE-Cys/CsNF biocomposites were much higher than those for the corresponding cured resins. SPE-Lys/ChNF and SPE-Cys/CsNF biocomposites exhibited higher tensile strengths and moduli than SPE-Lys and SPE-Cys did, respectively.