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Additive components



2

Outline

• Overview of Additives• Why they’re used• Functions of engine oil• The Challenge

• Basic Concepts• Polarity, Surfactants, and Micelles• Colloids and Emulsions• Radicals and Reactions

• Engine Processes and Additives• Oxidation and Antioxidants• Acids and Detergents• Deposits and Dispersants• Wear and Anti-Wear• Friction and Friction Modifiers

• Formulation• Putting it all together



3

What’s in the bottle*?

Additive Package

Base Stock

Viscosity Modifier

Dispersant

Detergent

Anti‐Oxidant

Anti‐Wear

Friction Modifiers

Others

Ensures fluidity andadds performance

Changestemperature response

Keeps everything soluble

Neutralizes acids andprevents deposits

Reduces and delaysoxidation

Reduces abrasive wear

Reduces (or increases)friction

As needed for specialized products

Hydraulic Oils &MonogradeEngine Oilsdon’t haveVM

*Not all oils haveall components

=**Many other, morespecialized additives



4

Functions of additives

• Make “oil” work

• Base stock by itself is not good enough for most applications

• Tailor base oils for different applications

• The same base stock can become PCEO, HDDO,ATF, Industrial Oil, etc., depending which additives are used

• There are some limitations

• Perform two critical functions:

• Minimize destructive processes

• Oxidation, wear, friction, corrosion, etc.

• Confer beneficial properties

• Lubricity, cleaning, etc.



5

OH H

Polarity

• Oil and Water Do Not Mix!• Water is a polar molecule

• Oxygen has greater affinity for electrons• Becomes partially negative

• Hydrogen becomes partially positive

• Molecule is neutral, but has separation of charge

• Oil is a non-polar molecule

• Carbon and hydrogen have roughly same affinity for electrons

• Molecular symmetry further reduces polarity

+

SN

Water

Oil



6

The challenge

• Engine lubricating oils are non-polar• Hydrocarbons

• Engines and their contents are polar• Metal surfaces

• Oxidation products

• Soot

• Sludge

• Varnish

• etc.

• How to make them mix?



7

Surfactants

• Molecules with both polar and non-polar sections

• Will orient based on polarity of medium• Interface

• Where two phases meet

• e.g., oil and water

• Polar ends in water

• Non-polar ends in oil

• In bulk liquid

Polar ‘head’ Non-polar ‘tail’



8

Micelles

• In three dimensions these form a spherical environment• Solid in the middle = colloid

• Liquid in the middle = emulsion

In Oil In WaterPolar core

Non-polar core



9

Chemistry shorthand

= RH RH is really R:HR:H R• + H•

Unpaired electron = Radical

C5H12 =(pentane)

CC

CC

C

H

H

HH

H

H

HH

H H

H

H

CC

CC

C



Oxidation



11

Chemically, what is oxidation?

• Destruction of molecules by exposure to oxygen atelevated temperatures

• Technically, oxidation can occur without oxygen, but we don’t need to consider those cases

• Initiated by Radicals

• Molecular fragments with an unpaired electron

• Very unstable and reactive

• Radicals attack and “pull apart” the base stock molecules

• To pair their lone electron

• The process can be catalyzed by metals

• Catalyzed = Accelerated



12

C

H

How to measure oxidation

Carbonyl

Polar

Acid

Larger molecule(higher viscosity)

1. Oxygen Uptake2. Infrared3. Acid Number4. Insolubles5. Viscosity Growth

+O2

+O2

Chain Breaking Chain Growth

Radical

OH

OH

H

C

O

C

H

H

C

O

OH

C

H

C

H



13

Indicators of oxidation

Aluminum Beaker Oxidation Test (ABOT)

0 10050

Test Hours

300250 350200150-10

0

10

20

30

40

50

Ch

ang

e (I

R,

Vis

cso

sity

)

-1

0

1

2

3

4

5

Ch

ang

e(P

entan

e, Acid

)

Infrared

AcidNumber

Viscosity

PentaneInsolubles



14

Runaway oxidation

Viscosity changes due to oxidation

Polymer Thickened Fluid

NOT TO SCALERelative sizes and

timings of decrease and

increase will vary

Chain breaking of

VMChain growth of base

stock

Break Point

Oxidation Inhibitor

Consumed

Vis

cosi

ty

Time



15

Anti-oxidant example

Source: Igarashi, et. al., J. Am. Chem. Soc. 1992, 114, 7727-7736

0 1000 2000 3000 4000 5000Time, seconds

0

50

100

150

200

250

Ext

ent

of

Oxi

dat

ion

, m

M[

–OO

H]

• Anti-oxidant displays “Induction Time” to delay onset of oxidation

– Followed by “Break Point” and resumption of oxidation

n‐hexadecane160C1 atm O2

1.2 mM BMPadded at 620 s

OH



16

Effect of temperature

Rule of thumb - every 10C increase in temperature doubles the rate of oxidation

140C

Test Temperature

This data set: Rate doubles

every 7°C

163°C

155°C

Aluminium Beaker Oxidation Test (ABOT)

170C

Test Hours

150 250200 300

Aci

d N

um

ber

Incr

ease

10

2

0

8

6

4



Oxidation inhibitors (or anti-oxidants)



18

Anti-oxidant

• Oxidation– Destruction of molecules by exposure to oxygen at elevated temperatures

• Negative consequences of oxidation– Viscosity increase– Acid formation

• Attack engine surfaces– Particularly copper-lead bearings

– Insolubles• Form deposits

– Sludge and varnish– Additive depletion

• Function of anti-oxidants– Reduce and control oxidation

• Compositions– Hindered Phenol– Alkylated DiPhenyl Amine– Some sulfur compounds– Certain metal compounds (e.g., Molybdenum)

HO

RHindered Phenol

N

R R

H

Alkylated DiPhenyl Amine

Hydrocarbon“tail” forsolubility



19

O

R

HH

C

C

HHH

HC

HH H

C

C

C

HH H H

H

H

HH H

OH

R

How do hindered phenols work?

• Easily lose a hydrogen to form a stable radical

• Stabilized by aromatic ring

• Further reaction inhibited by molecular structure

Is really

Hindered

Hydrocarbon tail for solubility

Bulky groups reduce further reactions

Weakly bonded hydrogen

Aromatic ring stabilizes radical

H.



Detergents



21

Detergents



22

Detergents

• Functions• Neutralize acids

• Combustion products: Sulfur and Nitrogen (strong) acids

• Oxidation products: organic (weak) acids

• Reduce high-temperature deposits• Prevent piston ring sticking

• Lacquer, varnish, and carbon

• Prevent bore polish (abrasive or corrosive liner wear)

• Mechanisms• Basic (alkaline) to neutralize acids

• Surface-active to reduce deposits

• Composition• Basic metal with organic “tail”

• Sulfonate

• Phenate

• Salicylate

Ca, Mg, Na, Ba, ….

Deposit prevention



23

Function of detergent

• Acid neutralization

OEM minimum

Bas

e N

um

ber

by

D47

39

0

3

6

9

0 20,000 40,000 60,000Miles

OEM oildrain interval

Oil AOil B

Oil C



24

Function of detergent

• Piston cleanliness



25

Detergents

Neutral

Basic

Overbased

'Soap'

'Core' (metal carbonate) (metal hydroxide)

H– O – M – O –H

H– O – M – O –H

CaCO3

Mg(OH)2

StrongInorganic

BaseH– O – M – O –H

“M” is a metal, such as calcium, magnesium, sodium, etc.



26

Typical lubricant detergents

M+

–O

R

O C

OH

O

M+

–

R

O S O

O

M+

–

R

Sulfonate Phenate Salicylate

“M” is a metal, such as calcium, magnesium, sodium, etc.“R” is a hydrocarbon “tail” for solubility



27

SASH and ash

• Detergents contain metal– Calcium, magnesium, sodium, etc.

• When burned, they leave a residue– Called “Ash”

• Typically measured as ”sulfated ash”

• React the oil with sulfuric acid and burn it• Simulates burning in the presence of fuel

• Metals become metal sulfates• Hydrocarbons burn completely

• Indirect method of measuring metal content• ASTM D874

• Note: There is also a test for ”ash”

• without sulfuric acid• ASTM D482



28

Base number

• Base Number (BN) is a quantitative measure of alkalinity• Formerly known as Total Base Number (TBN)

• Concentration of base• Expressed as equivalent KOH neutralizing ability (mg KOH/g units)

• Add acid until solution is neutralized• Two test methods

• ASTM D2896• Uses perchloric acid, an extremely strong acid• Measures “everything”

– Strong bases, weak bases, some salts, etc.• Gives higher numbers• Used for fresh oils

• ASTM D4739• Uses hydrochloric acid, a strong acid• Measures “effective”

– Strong bases• Gives lower numbers• Used for in-service oils



Dispersants



30

Dispersants

• Definition– Also called “Ashless Dispersants”– “Ash” really means “SASH” means “contains a metal”

• Sodium, calcium, magnesium, zinc, etc.• Dispersants don’t contain metals

• Only carbon, hydrogen, nitrogen, oxygen, boron, etc.

• Functions• Suspend (dissolve) soot• Inhibit and suspend sludge

• Sludge = oil + water + oxidation + dirt = “black mayonnaise”• Reduce formation of deposits• Keep things clean

• Engine oil is a trash collector• Oil change is “taking out the garbage”

• Composition• Long chain hydrocarbon for solubility• Small (non-metal) polar “head group” to stick to soot and deposits

Fuel additives callthese “detergents”

Detergent

Dispersant



31

N

O

O

Poly IsoButylene

Polar head

= PIBSA/PAM

Dispersants – composition

Non-Polar tail

Example:

PolyAMineIsoButylene

N N N NN

BridgingGroup

SuccinicAnhydride



32

Dispersant example

Bad Results Good Results



Friction and wear



34

Friction and wear

• Both are caused by relative motion between surfaces

• Friction is a loss of energy

• Dissipated as heat

• Heat can do damage

• Wear is a loss of material

• Changes geometry of contacts

• Changes equipment performance

• Introduces metal oxidation catalysts



Antiwear agents



36

Antiwear agents

• Function• Reduce surface-on-surface wear

• Mechanism• Decompose on the surface to form protective film• Heat caused by friction• “Anti-Flux” – dirty surface prevents adhesion

• Composition• Zinc-containing (ZDDP)

• Engine oils• Ashless phosphorus based

• ATF, gear, aviation• Ashless non-phosphorus

• Railroad and other special cases• Extreme pressure

• Gear oils

Consequence:



37

Phosphate

Dialkyl

Zinc Dithio

Zinc Dialkyl DithioPhosphate (ZDDP)

Note: Not exact chemical structure; for illustration only

RO ORS S

RO ORS S

P Zn P

Hydrocarbon 'tail' for solubility.Can be varied to affect performance

More detail about “R” group later



38

ZDDP “alkyl” structures

Alkyl type, length, and branching affect ZDDP properties

Primary ZDDP – one

‘alkyl’ group

Secondary ZDDP – two

‘alkyl’ groups

Aryl ZDDP – aromatic

group

ZnS

SP

OR

O Z

ZnS

SP

OR

O C

H

H

X

ZnS

SP

OR

O C

H

Y

X



39

0

20

40

60

80

100

150 200 250 350300

Wei

gh

t R

emai

nin

g, P

erce

nt

Temperature, Celsius

Thermo-Gravimetric Analysis (TGA)

ZDDP decomposition

ZDDP decomposition temperatures highly dependent on method and conditions

Good for passenger car sliding valve trains

Good for gas engine ring-liner wear

Good for marine cylinder oils



40

Ashless phosphorus type

• Tri-cresyl phosphate (TCP)• And variations

• Can substitute other chains for CH3

• Can substitute sulfurs for oxygens• Thiophosphate

• Can remove one oxygen to make phosphite

OCresyl

H3C CH3

CH3

O P O

O

Cresyl



41

Extreme pressure (EP) additives

• ‘Extreme’ is a relative term

• ZDDP sometimes called ‘EP’

• EP more commonly refers to

• Additives for high loads in gear oils

• Chlorine-containing molecules

• Highly reactive sulfur or sulfur-phosphorus compounds

• Work similar to ZDDP, but

• More active

• More corrosive

• Balance EP protection with corrosion

H3CCH3

Cl Cl Cl Cl

Cl Cl

Short-chain chlorinated paraffin

H3C CH3

Cl

Cl

Cl

Cl

Cl

Cl Cl

Medium-chain chlorinated paraffin

O

OClCl

Cl

Cl

Cl

Cl

O

O

R

R

Ester ofchlorendic acid

Trichloromethyl esterof thiophosphoric acid

PS S

O

SO

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

O

O



Friction modifiers



43

Metal surface

What are friction modifiers?

• Function• Reduce friction between contacting surfaces in relative motion

• Mechanism• Form a “springy” layer

• “Plush Carpet” effect

• Composition• Straight-chain stiff

hydrocarbons withpolar end groups

• Bond to metal surfaces

• Rather than soot, for example

Consequence:

FrictionModifier



44

Friction modifier example

• Stribeck curve• Friction modifier extends the hydrodynamic region

• Enabling protection at lower viscosities

Viscosity

Fri

ctio

n C

oef

fici

ent

(Po

wer

Lo

ss)

Without FM

With FM

Ref: Passut, C.A. and Kollman, R.E., SAE paper 780601



45

Typical friction modifiers

OH

O

O

OP OH

O

C O OH

C O

O

Oleic acid

Dioleyl phosphite

Glycerol dioleate



46

Solid friction modifiers

• ‘Flat Plate’ molecular geometry

• Planes glide over each other

• Graphite (Carbon)

• Molybdenum DiSulphide (MoS2)

• Polytetrafluoroethylene = PTFE

• Teflon®

• Strong terminal bonds don’t stick to other things



Comparison of additives



48

Relative sizes of things

Atom

Soap Molecule

Friction Modifier

Detergent Colloid

Virus

Dispersant

Viscosity Modifier

Surface Roughness

Soot Particles

Oil Film Thickness

Bacteria

Human Hair

Log (Meters)-10 -9 -8 -7 -6 -5 -4 -3

millionth inch

Ångstrom = Å

nanometer = nm

Oil Filters

Wear Particles

ISO Scale

micrometer= micron= µm

thousandthinch

millimeter = mm

billionth inch



Formulation(Putting it all together)



50

Formulation science

The key is balancing the additives for the application:

Antioxidants LOFI

Antiwear VM

Antirust Base Stock

Detergent

'The Oil'

Dispersant FM

ATFPCMO

HDEO2T

Gear

RRGEO

Indoil

For more information:“Lubricant Additives, Chemistry and Applications,” L. R. Rudnick (ed.), Marcel Dekker, Inc., 2003“Lubricant Chemistry, Technology, Selection, and Design,” S.Q.A. Rizvi, ASTM MNL59, 2009“Automotive Lubricants Reference Book (2e),” R.F. Haycock and J.E. Hillier, SAE PT‐111, 2004



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additive components - infineum insight...© 2018 infineum international limited. all rights...

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