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TRIBOLOGY - LUBRICANTS AND LUBRICATION Part 12

Tham khảo tài liệu 'tribology - lubricants and lubrication part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 212 Tribology - Lubricants and Lubrication decreases with increase of jojoba oil ratio in the prepared grease. It may be indicated also that on increasing the ratio jojoba oil additive to the prepared greases would increase binding and compatibility of the grease ingredient. As a result the dropping point values for prepared greases G2A G2B and G2C increased to 178 180 and 183 C respectively. Table 7 shows in general the positive effect of all concentrations of jojoba oil additive on the proprieties of G2A G2B and G2C. In this respect the 5 wt of additive of jojoba oil showed a marked improvements effect. Such improvements may be attributed to the unique properties of jojoba oil e.g. high viscosity index 257 surface tension 45 mN m and its chemical structure Wisniak 1987 . Based on these properties and correlation with the dropping point penetration oil separation oxidation stability dynamic viscosity consistency index and yield stress data its clear that the suitable and selective grease formula is G2C. Symbol Ingredient property G2A G2B G2C Test method G1g wt 99 97 95 1 Jojoba oil wt Penetration at 25 C 1 3 5 Un worked 284 278 277 worked 289 282 280 ASTM D-217 Dropping point C Oxidation Stability 99 96h 180 182 187 ASTM D-566 pressure drop psi 3.5 3.2 3.0 ASTM D-942 Alkalinity Wt Total acid number mg 0.16 0.14 0.14 ASTM D-664 KOH g @72h 0.20 0.18 0.16 ASTM D-664 Oil separation Wt Copper Corrosion 1.8 1.8 1.7 ASTM D-1724 3h 100 C Code Grease Ia Ia Ia ASTM D-4048 NLGI 2 2 2 Egyptian Standard Apparent Viscosity cP @ LB LB LB 90 C 39891 41090 41294 ASTM D-189 Yield stress D cm2 75.6 78.1 80.6 Four ball weld load Kg 188 190 195 ASTM D -2596 Table 7. Effect of addition of Jojoba oil on properties of the selected prepared grease G1G 3.4 Effect of the jojoba meal additive Because greases are colloidal systems they are sensitive to small amounts of additives. To study the effect of jojoba meal additive on the properties of the selected grease G2C five grades of lithium .