In order to reduce the consumption of energy caused by friction and wear, it is important to improve the tribological properties of polymer-based tribomaterials. In this study, we report the fabrication of cellulose nanofiber（CNF）/epoxy composites via CNF cryogels, which are porous materials prepared by a freezedrying technique, and their tribological properties were investigated. CNF/epoxy composites were prepared by impregnating epoxy resin into CNF cryogels and following curing processes, and their tribological properties were evaluated by a ball-on-disk reciprocating friction test. Resultantly, CNF/epoxy composites exhibited good wear-resistant properties whose specific wear rate was one-fourth of that of a pristine epoxy thermoset. Furthermore, multi-functional tribomaterials with thermal and electrical conductivity were designed by the addition of graphene platelets（GR）to the CNF/epoxy composites. In this case, CNF/GR cryogels with anisotropic honeycomb-like porous structures were also prepared using a freeze-casting method in addition to the randomly dispersed analogs. The characterizations of the CNF/GR/epoxy composites indicate that the honeycomb- like structures consisting of CNF and GR are effective in improving not only their thermal and electrical conductivity but also their wear-resistant properties.

Benzoxazine resin is an excellent thermosetting resin that not only has excellent hardness, heat resistance, flame retardancy, and electrical insulation properties, but also does not require acidic or basic catalysts during the curing process. Therefore, its use is expanding in fields related to adhesion, as a material useful for applications such as semiconductor encapsulants, printed wiring boards, insulating paints, and various resin modifiers. In this study, oligomers containing benzoxazine rings in their side chains were synthesized by radical copolymerization of maleimidobenzoxazines and vinyl monomers, and their thermosetting behavior was clarified. Selecting styrene, isobutyl vinyl ether, and methyl acrylate as vinyl monomers, the radical copolymerization of maleimidobenzoxazines containing an allyl group or phenyl group as an N-substituent was carried out in dimethyl sulfoxide at 60℃. As a result, oligomers with molecular weights ranging from several hundred to thousand were isolated as solid products insoluble in methanol. The thermal and mechanical properties of the thermoset products obtained by heating the obtained oligomers in the temperature range of 140℃ to 180℃ were investigated in detail.