Nucleophilic amino acids as a renewable alternative to petrochemically-derived amines in glycerol epoxy resins

The standard epoxy resin curing agents revealed are from unsustainable petroleum-based sources, which produce poisonous exhaust when cured. Amino acids, a bio-based epoxy curing agent with amino and carboxyl groups, are another potential curing agent. Water-soluble epoxy resins cured with lysine (Lys), glutamic acid (Glu), leucine (Leu), and serine (Ser) as amino acids were investigated. The results showed that the water-soluble epoxy resin (glycerol epoxy resins, GER) was cured with Lys and Glu after reacting. Fourier transform infrared (FT-IR) spectroscopic analysis of the GER-Lys showed that the amino and carboxyl groups of Lys primarily reacted with the epoxy groups of GER. The elongation at break of Lys-cured GER (GER-Lys) cured at 70 ℃ with a molar ratio of 1꞉0.75 was 75.32%. The fact that elongations at break of GER-Lys (79.43%) were higher than those of GER-Glu (17.33%), respectively supports the decrease of crosslinking density by the amino acid-cured GER reaction. The potential of Lys and Glu alternatives for petrochemical amines is demonstrated and provides promising opportunities for industrial application.