High-Performance One-Component Epoxy Adhesive Based on the Synergistic Effect of Lignin-Derived Triaryl-Imidazole and Phytic Acid

Latent curing agents are essential in the formulation of one-component epoxy resins, yet they are seldom derived from fully biobased chemicals. In the present work, a fully biobased latent curing agent for epoxy resins (BIMPA) was produced by synthesizing an ionic complex of lignin-derived triaryl-imidazole (BIM) and phytic acid (PA). Benefiting from the synergistic effect of BIM and PA, the one-component epoxy resin, composed of BIMPA and commercially available E51, exhibits a storage stability of over 90 days. Upon heating, the ionic complex undergoes decomposition, liberating the active imidazole to cure the precursor. The resulting epoxy resins exhibited a flexural modulus of 3.09 GPa, a flexural strength of 107.47 MPa, a notched izod impact strength of 2.47 kJ/m(3), and a shear strength of 41.02 MPa. The outcome can provide an effective supplement for the development of biobased epoxy resins.