Production of Lubricating Grease Using Non-Edible Soybean Sludge and Polypropylene as Complex Thickener
Keywords:
non-edible soybean oil; sodium grease; polypropylene; NLGI 2; water washout; dropping point; sustainable lubricantAbstract
Conventional lubricating greases rely heavily on petroleum-derived thickeners and edible vegetable oils, raising sustainability and food security concerns. Sodium-based greases are cost-effective but suffer from poor water resistance, limiting their industrial application. This study aimed to formulate and evaluate a sustainable sodium-based multipurpose grease using non-edible soybean oil as base saponifiable feedstock and polypropylene as a performance-enhancing additive. : Sodium soap was produced via saponification of pre-treated non-edible soybean oil with 26% NaOH solution. Six formulations (F1-F6) were prepared by varying sodium soap content (100-600 g) at constant polypropylene (20 g) and base oil 900N (200 g). Physicochemical properties were evaluated according to ASTM standards: worked penetration (ASTM D217), dropping point (ASTM D2265), water washout (ASTM D1264), free acidity/alkalinity (IP 37), and water content (ASTM D95). Worked penetration decreased from 295 to 265 dmm, placing all formulations in NLGI Grade 2. Dropping point increased from 162°C to 195°C, exceeding the 150°C ASTM minimum. Water washout decreased significantly from 35% to 15% with increasing soap content, with formulations F2-F6 meeting the <25% requirement. Free alkalinity (0.03-0.05%) and free acidity (0.70-0.85%) remained within acceptable limits. Formulation F4 (400 g soap) exhibited optimal balance with 270 dmm penetration, 185°C dropping point, 20% water washout, and good adhesiveness.
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