Enhanced interfacial interaction by grafting carboxylated-macromolecular chains on nanodiamond surfaces for epoxy-based thermosets

A novel core-shell-structured carboxylated-styrene butadiene rubber (XSBR)-functionalized nanodiamond (ND-XSBR) was synthesized and characterized. Epoxy (EP) nanocomposites toughened by pristine ND and ND-XSBR were investigated and compared. The ND-XSBR-reinforced nanocomposite exhibited mechanical properties superior to those of the one filled by pristine ND. At a low-filler loading, the ND-XSBR exhibited an impressive toughening effect. The maximum flexural strength was shown when the filler loading was as low as 0.1 wt % for the EP/ND-XSBR nanocomposite. Furthermore, enhanced fracture toughness and fracture energy were shown by surface functionalization, representing enhanced compatibility between the ND-XSBR and EP matrix. The glass transition temperature (T_g) and storage modulus of the nanocomposites were studied, and the EP/ND-XSBR0.1 nanocomposite exhibited the highest T_g owing to the stronger interfacial interaction. The EP/ND-XSBR0.2 exhibited higher storage modulus and T_g than the EP/ND0.2, because the higher interfacial interaction can restrict the molecular mobility of the EP by the functionalized ND-XSBR.