7 Technologies for Conversion Bio-Lubricant …
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7.2.3.1 Bio-Lubricant Additives
Plant oils used as base oils need to be selected from the following aspects: good
dispersion and dissolution of additives, excellent low-temperature properties, fine
lubricating properties, and high flash point. The inadequacies of plant oils such as
substandard oxidation stability, poor hydrolytic stability, deficient low-temperature
fluidity, blistering compared to mineral oil, and poor filterability can be improved by
adding appropriate additives [35].
Additives are chemical compounds that give the lubricants some special properties. Some additives make lubricants have new beneficial properties, for example,
cleanliness and dispersion, abrasion resistance, corrosion resistance, and emulsifying ability. Other additives can improve the existing performance of lubricants,
such as viscosity, viscosity index, pour point, antirust properties, and anti-oxidation
properties. Firstly, when additives are added to the lubricants, the real contact area
increases, the contact stress decreases, and non-smooth friction surface can be filled
and repaired. Secondly, because most additives are polar substances, they can react
with metal surfaces to form a chemisorbed film which has extreme pressure protection. Finally, when the friction surface is under local high temperature and highpressure conditions, additives can be decomposed to produce new substances. These
new substances can react with metals and yield a film which can prevent the surface
from gluing. These are the main processes by which additives play a protective role.
Lubricant additives have a variety of functions being divided into viscosity
index modifiers, detergent and dispersant additives, extreme pressure and anti-wear
additives, antioxidants, and other additives.
Viscosity Index Modifiers
Viscosity index modifiers are linear polymer compounds, which are soluble in hydrocarbon base oils. They are based on the difference in the viscosity of different forms
at different temperatures and improve the viscosity performance of the oil [15].
When the polymer shrinks and curls at low temperatures, they have a relatively
small effect on the viscosity. However, polymer swells at high temperatures, and
the internal friction of the base oil increases significantly, resulting in an obvious
increase in the viscosity of the base oil. The addition of the viscosity index modifiers
compensates for the disadvantages of decreasing the viscosity of lubricants caused
by the rise in temperature. The most commonly used viscosity index improvers
are hydrogenated styrene diene polymers, polymethacrylates, ethylene–propylene
copolymers, polyisobutylene, polyvinyl n-butyl ether, and so on.
Detergents and Dispersants
Lubricating oil can be oxidized at high temperatures. Oxidation products form
deposits, thus reducing the efficiency of the internal combustion engine. Therefore,
191
7.2.3.1 Bio-Lubricant Additives
Plant oils used as base oils need to be selected from the following aspects: good
dispersion and dissolution of additives, excellent low-temperature properties, fine
lubricating properties, and high flash point. The inadequacies of plant oils such as
substandard oxidation stability, poor hydrolytic stability, deficient low-temperature
fluidity, blistering compared to mineral oil, and poor filterability can be improved by
adding appropriate additives [35].
Additives are chemical compounds that give the lubricants some special properties. Some additives make lubricants have new beneficial properties, for example,
cleanliness and dispersion, abrasion resistance, corrosion resistance, and emulsifying ability. Other additives can improve the existing performance of lubricants,
such as viscosity, viscosity index, pour point, antirust properties, and anti-oxidation
properties. Firstly, when additives are added to the lubricants, the real contact area
increases, the contact stress decreases, and non-smooth friction surface can be filled
and repaired. Secondly, because most additives are polar substances, they can react
with metal surfaces to form a chemisorbed film which has extreme pressure protection. Finally, when the friction surface is under local high temperature and highpressure conditions, additives can be decomposed to produce new substances. These
new substances can react with metals and yield a film which can prevent the surface
from gluing. These are the main processes by which additives play a protective role.
Lubricant additives have a variety of functions being divided into viscosity
index modifiers, detergent and dispersant additives, extreme pressure and anti-wear
additives, antioxidants, and other additives.
Viscosity Index Modifiers
Viscosity index modifiers are linear polymer compounds, which are soluble in hydrocarbon base oils. They are based on the difference in the viscosity of different forms
at different temperatures and improve the viscosity performance of the oil [15].
When the polymer shrinks and curls at low temperatures, they have a relatively
small effect on the viscosity. However, polymer swells at high temperatures, and
the internal friction of the base oil increases significantly, resulting in an obvious
increase in the viscosity of the base oil. The addition of the viscosity index modifiers
compensates for the disadvantages of decreasing the viscosity of lubricants caused
by the rise in temperature. The most commonly used viscosity index improvers
are hydrogenated styrene diene polymers, polymethacrylates, ethylene–propylene
copolymers, polyisobutylene, polyvinyl n-butyl ether, and so on.
Detergents and Dispersants
Lubricating oil can be oxidized at high temperatures. Oxidation products form
deposits, thus reducing the efficiency of the internal combustion engine. Therefore,