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Lubrication Fundamentals 2011 Part 4

Tham khảo tài liệu 'lubrication fundamentals 2011 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CH2 - CH2 CH2 - CH2 - 0 - CH2 CHj III I n I OH OH OH OH Ethylene Glycol Polyethylene Glycol Ether Figure 5.8 Glycols. Ethylene glycol is the simplest glycol when polymerized the oxygen bond is formed and it becomes a polyglycol ether. for the bulk of the materials used in lubricants. Small quantities of simple glycols such as ethylene and polyethylene glycol are also used as hydraulic brake fluids. Typical structures for the two types are shown in Figure 5.8. Polyglycols are polymers made from ethylene oxide EO propylene oxide PO or their derivatives. The primary raw materials are ethylene or propylene oxidized to form cyclic ethers alkylene oxides . Combining ethers derived from ethylene oxide EO to propylene oxide PO has a profound effect on the solubility of the product in other fluids EO PO 4 1 Water-soluble not soluble in hydrocarbons EO PO 1 1 Soluble in cold water soluble in alcohol and glycol ethers not soluble in hydrocarbons EO PO 0 1 Not soluble in water conditionally soluble in hydrocarbons These comparisons help explain the differences between the various types of and uses for polyglycol automotive antifreeze brake fluid water-based hydraulic fluids hydrocarbon gas compressors and high temperature bearing lubricants. In addition to ethylene and propylene oxides butylene oxide is used to provide some polyglycols with specific properties and is oil soluble. Polyglycols made with butylene oxide are more expensive and do not exhibit traction coefficients equal to combinations of EO and PO. One of the major advantages of polyglycols is that they decompose completely to volatile compounds under high temperature oxidizing conditions. This results in low sludge buildup under moderate to high operating temperatures or complete decomposition without leaving deposits in certain extremely hot applications. Polyglycols have good viscosity-temperature characteristics although at low temperatures they tend to become somewhat more viscous than some of the other .