Boron Compounds As Additives to Lubricants:

Synthesis, Characterization and Tribological Optimization

Faiz Ullah Shah

Tribology

The science and technology of interacting surfaces in relative motion

Tribology covers the fields of:

Friction

Wear

Lubrication

Chemical aspects of tribofilm formation

Friction

Additivemolecules Metal

Metal

FrictionTribofilmformation TribofilmInteraction

Base Oil

In boundary and mixed lubrication conditions, the lubricant additives interact with metal surfaces forming thin layers on the surfaces called tribofilms

Chemistry of ZnDTPsZnDTPs were first introduced in 1940s and are still being used in lubricants

They are known as multifunctional additives

N. D. Spencer et al. Tribol. Lett. 28 (2007) 209–222

STEEL

STEEL

ZnDTPs: Environmental and health hazards

2 NO N2 O2

2 NO2 N2 2 O2Pt/Rh/Pd

Pt/Rh/Pd

+

+

Reduction

Oxidation

ZnDTPs

Eye irritation

Mutagenicity

Allergic contact dermatitisC. M. Cisson et al. Lubri. Sci. 8 (1996) 145-177.

M. Isaksson et al. Contact dermatitis 48 (2002) 248-249.

2 CO O2 2 CO2Pt/Rh/Pd

+

Research Objectives

To develop a new class of lubricant additives that contains borate and dialkyldithiophosphate groups

To characterize chemical structures of these novel compounds

To study the effect of temperature on their physicochemical properties such as thermal stability, weight loss, and a pathway of fragmentation of these compounds as a result of thermal decomposition

To perform tribological evaluations of these new additives in comparison with commercial ZnDTP

Chemical SynthesisS-Di-n-octoxyboron-O,O’-di-n-octyldithiophosphate (DOB-DTP)

RO

RO

P

S

S B

OR

OR

(RO)3BP2S5 +24

[(RO)2B]2S

toluene, 3h, reflux

+

B(RO)3ROH+B(OH)3 3toluene, 3h, reflux

3 H2O+

R = C8H17

S-Di-n-octoxyboron-O,O’-di-n-octyldithiophosphate was synthesized by the following two steps

Step 2: S-Di-n-octoxyboron-O,O’-di-n-octyldithiophosphate

Step 1: Trioctyl borate (TOC)

I. S. Nizamov et al. Heteroat. Chem. 11 (2000) 102-106

Antiwear Performance of DOB-DTP

RO

RO

P

S

S B

OR

OR

Tribological Characterization

S = 0.093 %P = 0.045 % S = 0.139 %

P = 0.067%

S = 0.041 %P = 0.020 %

S = 0.061 %P = 0.031%

Shah, Glavatskih, Antzutkin. ACS appl. mater. Interfaces (2009) In press

Friction Performance of DOB-DTP

Tribological Characterization

Base Oil (BO) + 0.1 wt % additives Base Oil (BO) + 1.0 wt % additives

Shah, Glavatskih, Antzutkin. ACS appl. mater. Interfaces (2009) In press

Base Oil (BO)

BO + 1.0 wt % ZnDTP BO + 1.0 wt % DOB-DTP

3-D images of worn steel ball surfaces

SEM-EDS Analysis of tribofilms

Base oil (BO)

Base oil (BO) with 1.0 wt % ZnDTP

Shah, Glavatskih, Antzutkin. ACS appl. mater. Interfaces (2009) In press

SEM-EDS Analysis of tribofilms

Base oil (BO) with 1.0 wt % DOB-DTP

Shah, Glavatskih, Antzutkin. ACS appl. mater. Interfaces (2009) In press

Conclusions

Novel ashless boron derivatives of dialkyldithiophosphates with long alkyl groups were successfully synthesized using multi-steps reactions

These novel compounds have reduced amounts of sulphur and phosphorus, which make them environmentally friendly

The chemical structures of the resulting products were characterized by the elemental analysis, FT-IR and 1H, 13C, 31P and 11B NMR spectroscopy

The synthesized boron compounds have better antiwear and friction properties than ZnDTP

Their excellent tribological properties, high thermal stability and good miscibility with mineral oil make them an attractive alternatives to ZnDTP

Acknowledgment

Professor Oleg N. Antzutkin

Professor Sergei Glavatskih

Professor Erik Höglund

Associate Professor Mats Linberg

Associate Professor Allan Holmgren

Dr Ryan Robinson

My colleagues at the Division of Chemical Engineering and Division of Machine Elements