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Petroleum & Petrochemical Engineering Journal Research Article 7 min read

Types, Examples and Working Mechanism of Rheo-Improvers Lubricating Oil Additives

Rasha S Kamal*
* Corresponding author
ISSN: 2578-4846  10.23880/ppej-16000162  Received: June 10, 2018  Published: June 22, 2018
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Keywords
Rheo- improvers Viscosity index improvers Pour point depressant
Abstract

Lube oil additives play an important role to facilitate our daily life. And the most important one is Rheo-Improve lubricating oil additive, because it is performance enhancing additive it consists of two type viscosity index improvers and pour point depressants. This mini review highlights of Rheo-Improvers importance. Viscosity modifier (preparationof some examples, general properties, working mechanism and factors that limit their action). Pour point depressants (examples, general properties, working mechanism).

Introduction

The major role in the science is how to make life so easy and eco-friendly. Lubrication is a feature of how to live an easy life. Lubrication in simply form is the use of material to improve one surfaces over another by using lubricant. Lube oil additives are chemical components or blend used at a specific treat rate, generally from 1 to 35 % of the oil volume, depending on the machine to provide one or more functions in the fluid. Some additives impart specific property to the base oil or suppress undesirable base oil properties and finally others enhance existing base oil properties. Lubricant is additive with oil mixed together to give very good efficiency and save the metal from friction and wear. There are many type of additives and today we will take about an important one (Rheo- improvers).

According to new classification of lubricating oil additives which depending on the working function the additives classify into 3 major category:

  1. Rheo- improvers
  2. Maintainers
  3. Tribo-improvers

Rheo-Improvers (Rheological Properties Improvers)

Rheo-Improvers are responsible for fluidity of base oil. They contribute mainly under hydrodynamic conditions to the lubrication performance by changing or modifying the bulk properties of the liquid. They are lubricating performance additives. Rheological Properties Improvers could be categorized as tribo-improvers “indirect” between regimes of hydrodynamic and mixed lubrication [1].

Viscosity Modifier

The most important property of the oil is viscosity. Formerly, viscosity modifier (VM) which can called also viscosity index improvers (VII) that reduce the rate of viscosity change with temperature. It is one of the Examples [10]:

performance additives engine lubricants. The bulk properties are dependent on the structure of the base fluids [1]. Structural features of VM are polymers and copolymers [2, 3, 4, 5, 6, 7, 8, 9].

Some Examples of Viscosity ModifiersChemical Structure
SIP: styrene-co- isoprene
OCP: olefin copolymers and the major
classes are poly alkyl methacrylate and
poly isobutylenes.
Figure 1: Working Mechanism of Viscosity Modifier.
Click to enlarge
Figure 1: Working Mechanism of Viscosity Modifier.

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$$ \mathbf {C} $$ $$ \text {P o l y a l k y m e t h a c y l a t e} $$

$$ \mathrm {C H} _ {3} $$

$$ \mathrm {C H} _ {2} $$

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$$ [ 0 ] $$ Rasha S Kamal. Types, Examples and Working Mechanism of Rheo-Improvers Lubricating Oil Additives. Pet Petro Chem Eng J 2018, 2(2): 000162.

PMA : polymethacrylates preparation

Figure 2: Working Mechanism of Pour Point Depressants.
Click to enlarge
Figure 2: Working Mechanism of Pour Point Depressants.

SPE: Styrene Poly Ester

Mechanism of Viscosity Index Improver: Polymers molecules expands as the temperature is raised, due to the

polymer so to make degradation need trace of peroxides catalyst not affect by temperature); 3. Compatibility with other additives present in the oil [10] Factors that Limit the Action of Viscosity Modifiers

  1. Nature of the base oil (chemical structure of base oil);
  2. Concentration of the additive (an optimum concentration);

Rasha S Kamal. Types, Examples and Working Mechanism of Rheo-Improvers Lubricating Oil Additives. Pet Petro Chem Eng J 2018, 2(2): 000162.

3. Molecular weight of the additive (increase the molecular weight increase the efficiency as viscosity modifier until limited weight); 4. Polymer composition (effect of the substituted radical, R); 5. Pressure (due to relationship between the pressure and temperature) [10, 2]. Pour Point Depressants Pour point depressant is one of the performance additives engine lubricants [10]. The pour point is defined as enable lubricant to flow at low temperatures. The pour of an oil has been considered for a long time as the principal properties affecting the cold starting of an engine. At very low temperature the oil freeze (oil cannot pour or flow) that causes damage to the machine elements and although uses the pre-heating system but loose time and energy [1]. The reason of pour less is after refining and get lubricating oil there are fine wax crystals in the mineral oil which accumulate together under low temperature and make a lattice interlocking network which absorb the oil and prevent its pour or flow, so here appear the important of pour point depressant [15, 16, 17, 18, 19, 20, 21, 22, 23, 24].

Structural features of pour point depressant (PPD) are polymers can be used to interfere with wax crystal growth and alter the formation of the interlocking network for examples: Examples Polymethacrylates at Concentration of 0.1 to 0.5%

Figure 3
Click to enlarge
Figure 3

Alkylated wax naphthalene

Long Chain Alkyl Phenols (Tetra Paraffin Phenol)[10]

Di (Tetra Paraffin Phenol) Phthalate

Esterification of Styrene-Maleic Anhydride Copolymer as Pour Point Depressant

This copolymer by using docosanol as an alcohol and in concentration 0.0625% give very good result as pour point depressant ≥ -24 [10, 14].

Rasha S Kamal. Types, Examples and Working Mechanism of Rheo-Improvers Lubricating Oil Additives. Pet Petro Chem Eng J 2018, 2(2): 000162.

Mechanism of Pour Point Depressant

When oil subjected to very low temperatures (freeze) may undergo changes in their physical properties:- 1. Solidification but without precipitation of a solid phase; 2. Solidification with precipitation of a solid phase [25, 26, 27]. This solid phase may be according to size divided to a) Macrocrystals of paraffins which cause total solidification of oil. b) Microcrystals of wax which swell, forming a crystalline structure trapping a significant volume of oil [10, 14], so pour point depressant mechanism in simply way it means modify wax crystal formation to reduce interlocking at low temperatures and increase mobility of wax crystal around the flexible pour point depressants allowing the oil to continue to flow by adsorbed this type of additives on the wax crystals and inhibit the growth of a lattice interlocking network [1, 13, 15].

Figure 4
Click to enlarge
Figure 4

References

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@article{rasha2018,
  title   = {Types, Examples and Working Mechanism of Rheo-Improvers Lubricating Oil Additives},
  author  = {Rasha S Kamal},
  journal = {Petroleum & Petrochemical Engineering Journal},
  year    = {2018},
  volume  = {2},
  number  = {2},
  doi     = {10.23880/ppej-16000162}
}
Rasha S Kamal (2018). Types, Examples and Working Mechanism of Rheo-Improvers Lubricating Oil Additives. Petroleum & Petrochemical Engineering Journal, 2(2). https://doi.org/10.23880/ppej-16000162
TY  - JOUR
TI  - Types, Examples and Working Mechanism of Rheo-Improvers Lubricating Oil Additives
AU  - Rasha S Kamal
JO  - Petroleum & Petrochemical Engineering Journal
PY  - 2018
VL  - 2
IS  - 2
DO  - 10.23880/ppej-16000162
ER  -