An Investigation on the Lubricity Characteristics of Polyethylene Glycol Blends with Cellulose Palmitates

Three cellulose palmitate samples, viz Cell-Plam-A, Cell-Palm-B and Cell-Palm-C, were synthesized by known esterification reaction between microcrystalline cellulose and varying molar ratios of palmitoyl chloride (CH3(CH2)14COOCl). A combination of N,N-dimethylacetamide (DMAc) and lithium chloride (LiCl) is used as a solvent, while DMAP (4-dimethylaminopyridine) was used as catalyst. The three samples with different degree of substitution (DS) were then characterized using infrared, nuclear magnetic resonance spectroscopy, elemental analysis (CHN), thermogravimetry, scanning electron microscopy and X-ray diffraction to confirm the conversion of the cellulose into the cellulose fatty ester. Cell-Plam-A, Cell-Palm-B and Cell-Palm-C were found to have DS values 1.85, 2.37 and 2.63, respectively. The synthesized cellulose palmitate samples were then tested for lubricity properties in terms of wear scar diameter (WSD) and friction coefficient using a high-frequency reciprocating rig following modified ASTM D6079. It was found that the 3 % Cell-Plam-C in PEG-200 reduces the WSD from 560 to 503 µm, while the average friction coefficient decreases from 0.079 to 0.048.