Research on the Superlubricity of Lotus Root Starch/Carbon Nanotube Composite Water-Based Lubricant

Lubricants are widely used in the mechanical, electronic, and medical fields; however, traditional mineral oil-based lubricants cause environmental pollution. Therefore, the search for renewable, nontoxic, and environmentally friendly lubricants has become a current research focus. In this study, a lotus root starch (LRS)/carbon nanotube (CNT) composite water-based lubricant was introduced into a lotus root starch water-based lubricant, and frictional experiments were conducted using a GCr15-SiC ball-on-disk tribopair. Additionally, by investigating the formation mechanism of the polarization electric field between friction pairs, the enhancing effect of the lotus root starch particles and CNTs in the composite lubricant on the polarization electric field was explored. Finally, the lubrication and friction reduction mechanisms of the lotus root starch/CNT composite water-based lubricant were elaborated in detail. The results showed that the LRS2.5%/0.075%CNT lubricant exhibited excellent superlubricity under medium- and high-speed conditions (1200 and 1800 rpm, respectively), with a friction coefficient as low as 0.004–0.005. Furthermore, the lubricant showed good robustness during the 120 min experiment and could enter the superlubricity stage within a short running-in period (180 s). A study of the polarization electric field at the interface revealed that the LRS2.5%/0.075%CNT composite lubricant promoted the formation of a polarization electric field on mutually repulsive friction surfaces, significantly enhancing the load-bearing capacity of the tribopair. The findings of this study provide an important reference for the development of green lubricants with significant environmental benefits and application value.