Lubricant Properties
Petroleum Oils
The vast majority of lubricants in use today are mineral oils which are obtained through the distillation
of crude petroleum. Mineral oils are composed primarily of three types of hydrocarbon structures:
paraf?nic, aromatic, and alicyclic (naphthenic). The molecular weights of the hydrocarbons range from
about 250 for low-viscosity grades, up to nearly 1000 for more-viscous lubricants.
Mineral oils by themselves do not have all of the properties required of modern lubricants. For that
reason, almost all current lubricants are forti?ed with a chemical additive package which consists of
some of the following:
Oxidation inhibitors limit oxidation of hydrocarbon molecules by interrupting the hydroperoxide chain
reaction.
Rust inhibitors are surface-active additives that preferentially adsorb on iron or steel surfaces and
prevent their corrosion by moisture.
Antiwear and extreme pressure agents form low shear strength ?lms on metallic surfaces which limit
friction and wear, particularly in concentrated contacts.
Friction modi?ers form adsorbed or chemisorbed surface ?lms which are effective in reducing friction
of bearings during low-speed operation (boundary lubrication regime).
Detergents and dispersants reduce deposits of oil-insoluble compounds (e.g., sludge) in internal
combustion engines.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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