Toughening Effect of Rod-like Cellulose Nanocrystals in Epoxy Adhesive

Epoxy structural adhesives have been used extensively in the automotive and aerospace industries to bond assembly parts. Much effort has been devoted to enhancing the mechanical properties of epoxy resin by incorporating fillers. Among a variety of fillers investigated for this purpose, nanocelluloses are regarded as a promising type of emerging green filler material because of their excellent mechanical and physicochemical properties. Indeed, nanocelluloses have been used as a filler for polymer nanocomposites. However, the toughening and reinforcing effects of nanocelluloses on rigid epoxy adhesives have not yet been fully revealed, particularly from the perspective of adhesive bonded joints. Here we report that epoxy adhesive containing highly dispersed cellulose nanocrystals (CNCs) produced using a solvent-free ball milling method achieves drastically improved adhesive strength and fracture toughness compared with that of the reference adhesive without CNCs. The epoxy adhesive containing dispersed CNC...