The scope of this study is investigating the tribological characteristics of prepared bio-based thread grease from renewable sources with polymerization products from jojoba oil as additives. Accordingly, the first part in this study aims to prepare three molecular weights grades from polymerized jojoba oil using microwave technique. The physicochemical and tribological properties of jojoba oil and its polymerized were determined . their tribological behavior studied in term of coefficient of friction and wear scar diameter using four ball machines. The results revealed that the polymerized jojoba with low molecular weight shows the lowest friction coefficient and wear scar diameter compared with high molecular weight polymerized jojoba grades and jojoba oil before polymerization. This has been discussed based on the unique properties of the chemical structure of jojoba.
Studying three independent variables that affecting to coefficient of friction and wear scare diameter. using regression analysis. The studied affecting independent variables are the load, the velocity (revolution per minute, RPM) and the polymerization time. ,Optimization of these variables showed that minimum FCO and WSD could be achieved after polymerization time of 1.2 hr, under load of 196 N with a speed of 600 rpm. .
It was concluded that the polymerized jojoba grade with low molecular weight has superior tribological performance and could be used as a significant potential additive for bio-based thread grease in the next part of this study.