High Performance of Cellulose Nanocrystal Based Bicomponent Supramolecular Hydrogel Lubricants

AbstractsCellulose nanocrystal based bicomponent supramolecular hydrogel (CNC/x-DG/y) was prepared by a simple mixing method using CNC and diglycerol (DG) as gelators. Once deionized water is set at 1 mL, CNC/x-DG/y hydrogel becomes stronger with increasing CNC content (no less than 2.4 wt%), but weakened with enhancing DG content (0.1~1.3 mL). The gelling mechanism is attributed to multiple H-bonds between DG and CNC, which can self-assemble into a three-dimensional network to effectively trap water molecules. CNC/x-DG/y hydrogel shows many advantages for lubrication application, including reversible shear thinning behaviours, satisfactory viscoelasticity, excellent creep recovery performances, outstanding anti-rust property and much lower water volatilization rate, which exactly have improved the drawbacks of water-based lubricants. CNC/2.4-DG/0.1, a typical CNC/x-DG/y hydrogel, exhibits excellent tribological performances which are deeply dependent on the applied load and the reciprocating frequency. The friction coefficient and wear volume for CNC/2.4-DG/0.1 are 0.059 and 0.81×10-3 mm3, apparently lower than those for two reference lubricants. The high performance for reducing friction and wear of CNC/2.4-DG/0.1 can be ascribed to the synergistic mending effect of CNC nanoneedles and DG molecules and the dissipative effect caused by H-bonds between CNC nanoneedles and DG molecules.