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Soybean oil (SBO)‐based grease, containing polysoaps synthesized from polymeric epoxidized soybean oil (PESO), were investigated. Greases were prepared using a mixture of lithium soap and triethanolammonium polysoap. Grease properties investigated were hardness, using the cone penetration procedure (ASTM D217); oxidation stability, using the pressurized differential scanning calorimetry (PDSC) method (ASTM D‐5483); and friction and wear, using a four‐ball tribometer (ASTM D‐2266). Penetration data showed that grease formulated in the presence of polysoap was harder than that without polysoap, and this was attributed to the cross‐linking in the polysoap structure, which was expected to provide higher resistance to deformation. The PDSC results indicated that the onset temperature of grease formulated with 3.8 and 7.3 wt% polysoap increased by 8 and 12°C, respectively, compared to grease without polysoap. The coefficient of friction of grease formulated with polysoap was much lower (0.015) than grease without polysoap (0.034).
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