Activated Carbon Nano-Particles from Recycled Polymers Waste as a Novel Nano-Additive to Grease Lubrication

Abstract

A worldwide growing trend is dedicated towards reducing carbon dioxide emissions from mechanical systems in different industries. One key factor under focus of research is to decrease energy losses in rotating machinery during operation by improving lubrication performance. This paper presents a novel grease nano-additive using activated carbon (AC) as a byproduct from recycled polymer waste. Five different concentrations of AC nanoparticles (ACNPs) are added to lithium grease to obtain blends containing 0.025 wt.%, 0.05 wt.%, 0.1 wt.%, 0.5 wt.%, and 1 wt.%. The tribological assessment of blends has been performed using a four-ball wear test and load carrying capacity test. The obtained results for blends are compared to samples of base grease and to blends with 2 wt.% reduced graphene oxide (rGO). Test results showed a remarkable enhancement of load carrying capacity of AC samples by 20–30% as compared to base grease. By observing wear scar in rolling elements, the ACNPs lowered the average wear scar diameter (WSD) for all samples by 30–36%. Base grease samples showed the highest coefficient of friction (COF) values between 0.15 and 0.17. These values are reduced to 0.03 and 0.06 for grease with ACNPs reaching their minimum in the case of 1 wt.% AC. These outcomes are found consistent with the enhancements in driving power saving values. The results proved the competitiveness and suitability of the AC as a recycled waste and nano-additive for improving the tribological performance of grease lubrication.