The environmental impact imposed by mineral based lubricant and the threat of petroleum depletion has triggered this study to search for an alternative lubricant using commercialized palm oil. The low oxidation stability of vegetable oil limits the performance of palm oil as a lubricant. This study introduces Zinc Dialkyldithiophosphate  (ZDDP) and Zinc Diamlydithiocarbamate (ZDDC) into commercialized palm oil at different concentrations to investigate the effect of oxidation stability using a Rotating Pressure Vessel Oxidation Test. This study discovered that ZDDP displayed a better performance compared to ZDDC in terms of oxidation stability where it exhibited a longer oxidation time of 128 minutes at a concentration of 2 wt%. It can be concluded that the addition of organo zinc compound had improved the oxidation stability of commercialized palm oil as lubricant

Azhari, Muhamad Azwar

Md Sallehan, Muhammad Syafi

Nazri, Muhammad Naqib

Universiti Teknologi MARA Institutional Repository

Journal of Mechanical Engineering                                                            Vol SI 4(2),23-29, 2017                                                      
___________________ 
ISSN 1823- 5514, eISSN 2550-164X                              Received for review: 2017-02-14                                                                              
© 2017 Faculty of Mechanical Engineering,                        Accepted for publication: 2017-06-01 
Universiti Teknologi MARA (UiTM), Malaysia.                                         Published: 2017-09-15 
Oxidation Stability Comparison 
between Zinc 
Dialkyldithiophosphate and Zinc 
Diamyldithiocarbarmate Induced 
Palm Oil Bio-lubricants 
 
 
Muhamad Azwar Azhari
*
, Muhammad Syafi Md Sallehan,  
Muhammad Naqib Nazri 
Faculty of Engineering Technology, Universiti Teknikal Malaysia Melaka,  
Melaka, Malaysia 
 
*azwar@utem.edu.my 
 
ABSTRACT 
 
The environmental impact imposed by mineral based lubricant and the threat 
of petroleum depletion has triggered this study to search for an alternative 
lubricant using commercialized palm oil. The low oxidation stability of 
vegetable oil limits the performance of palm oil as a lubricant. This study 
introduces Zinc Dialkyldithiophosphate (ZDDP) and Zinc 
Diamlydithiocarbamate (ZDDC) into commercialized palm oil at different 
concentrations to investigate the effect of oxidation stability using a Rotating 
Pressure Vessel Oxidation Test. This study discovered that ZDDP displayed 
a better performance compared to ZDDC in terms of oxidation stability 
where it exhibited a longer oxidation time of 128 minutes at a concentration 
of 2 wt%. It can be concluded that the addition of organo zinc compound had 
improved the oxidation stability of commercialized palm oil as lubricant. 
Keywords: Palm oil, ZDDP, ZDDC, Bio-lubricant 
 
 
Introduction 
 
Lubricant is a substance that is applied between two contacting surfaces to 
reduce friction, minimize wear and reduce heat [1]. At present, most of the 
lubricant used either domestically or in the industry is derived from 
petroleum sources. With the current scenario of unstable petroleum crude 
Muhamad Azwar bin Azhari  et al. 
 
24 
 
 
prices due to the depletion of sources, added with the adverse environmental 
effect that the mineral based lubricant imposed on the environment, several 
studies have been done in order to search for an alternative substitute to 
petroleum based lubricant [2]. 
To date, numerous studies have been conducted by researchers to 
replace petroleum based lubricant. The most suitable candidate as base stock 
is seen to be oils derived from vegetable sources. Vegetable oil based 
lubricant are non-toxic and biodegradable compared to conventional 
petroleum based lubricant [3]. Vegetable oil also exhibits good properties, 
such as excellent lubricity, high viscosity index and high flash point that 
makes vegetable oil a suitable candidate to replace petroleum as base stock 
for lubricant production [4]. Lubricant derived from vegetable and animal 
fats have been used since 1650 BC where the Egyptians used animal fats to 
lubricate wheels of chariots and whale fats were used to lubricate equipment 
and other machinery [5]. However, these superior characteristics that 
vegetable oil possess has a weakness as vegetable consist of mono and poly 
unsaturated fats. According to Azhari et al., the high substance of unsaturated 
fats in vegetable oils makes the oil less cooperative to stabilize any oxidation 
process [6]. Heat and oxygen from lubrication process will accelerate the 
oxidation process of vegetable oil based lubricant. In general, oxidation starts 
with an initiation process when an external force separating the hydrogen 
from the chain producing free radicals. The free radicals will then react with 
oxygen to produce peroxy radicals. Following the next steps of oxidation 
process is propagation process. In this process, peroxide radicals will form 
more radicals through reaction with more components in the lubricants. The 
completion of branching and termination process in oxidation will result in a 
longer chain of carbon molecules [7]. The steps of oxidation are displayed as 
in Table 1. 
Oxidation needs to be delayed if not suppressed as oxidation will 
reduce the function of lubricant in lubrication process. The process of 
oxidation will cause the kinematic viscosity of oil to increase and this will 
contribute the increment of friction and wear on the internal surfaces of the 
machine. 
This oxidation process may be suppressed by using anti-oxidant 
additives. Organo zinc compounds such as Zinc dialkyldithiophosphate 
(ZDDP) and Zinc diamyldithiocarbarmate (ZDDC) can be used as an anti-
oxidizing agents and it also improves anti-oxidation performance in 
lubricating oil [8]. Antioxidants are added into lubricant base stocks in order 
to decrease the rate of oxidation in lubricating oil which is particularly 
important at elevated temperature [9]. Apart from that antioxidants end these 
chain responsed by most likely uprooting free radical intermediates, or by 
being oxidizing themselves. Consequently, most cell reinforcements are 
frequently decreasing agents [10]. 
Oxidation Stability Comparison between Zinc Dialkyldithiophosphatel  
 
25 
 
 
Table 1: Lubricating oil oxidation process 
 
Steps Equation 
Initiation RH → R● + H● 
  R● + O₂ → ROO● 
Propagation ROO● + RH → ROOH + R● 
  ROOH → RO● +●OH 
Branching RO● + RH → ROH + R● 
  ●OH + RH → H₂O + R● 
Termination R● + R● → R-R 
 
While adding anti-oxidation agent is seem necessary to reduce the 
oxidation process upon lubricants, concentrations of the anti-oxidants added 
shall be controlled. Azhari et al., and Mahipal et al., studied the desirable 
concentrations of zinc additives in vegetable oil to investigate the 
improvement of tribological properties with the addition of ZDDP [11, 3]. 
From the studies, it is evident that the most desirable concentrations of ZDDP 
to be added into any type of vegetable oil shall be at 2 wt% or below. 
Therefore this study investigated the effect of different organo zinc substance 
which is ZDDP and ZDDC on the suppression of oxidation in vegetable oil 
based lubricant with addition of additive not more than 2 wt%. 
 
Methodology 
 
Commercial palm oil was purchased from local store and used as is. ZDDP 
and ZDDC was purchased and used without any prior modification. Seven 
samples were prepared with variation of zinc additives and concentration. 
ZDDP was added into commercialized palm oil at 1.2 wt%, 1.6 wt% and 2 
wt% concentration. ZDDC was also introduced to the commercialized palm 
oil at the same concentration. A control sample with 0 wt% addition of 
additive was also prepared using the same commercialized palm oil. Upon 
introduction of additives, the samples were immersed in a heated water bath 
at 50°C for 20 minutes to ensure dilution. 
After sample preparation, the samples were then tested for oxidation 
properties using a Rotating Pressure Vessel Oxidation Test in accordance to 
ASTM D2272. The samples were pressurized to 90 psi with oxygen and 
thermally heated to 150°C using steel pressure of water and copper coil 
catalysts reached a pressure drop of 25 psi was seen. 
 
 
Muhamad Azwar bin Azhari  et al. 
 
26 
 
 
Result and Discussion 
 
The samples were tested using a rotating pressure vessel oxidation test to 
investigate the oxidation stability of the lubricant oil added with ZDDP and 
ZDDC additives. The result of each oxidation test is per tabulated in Table 2 
and depicted as in Figure 1. 
 
Table 2: Rotating Pressure Vessel Oxidation Test 
Sample Time Taken (minutes) 
Pure Palm Oil 32 
1.2wt% ZDDC 52 
1.6wt% ZDDC 59 
2.0wt% ZDDC 62 
1.2wt% ZDDP 111 
1.6wt% ZDDP 124 
2.0wt% ZDDP 128 
 
From the experiments, it is evident that the oxidation time for pure palm oil 
reads at 32 minutes. This is clear that the pure palm oil takes a very short 
time to completely oxidize during the oxidation test. However, with the 
addition of ZDDC, the time taken for palm oil to oxidize gradually increase. 
At a concentration of 1.2 wt% ZDDC, the time taken for the sample to 
completely oxidize was recorded at 52 minutes. However, at 1.6 wt% and 2.0 
wt%, the oxidizing time for the samples continue to increase to 56 and 62 
minutes respectively.  This shows that the oxidation stability of the samples 
added with ZDDC are improved with the presence of Anti-oxidizing agent 
ZDDC. The additive ZDDC is known to mutually function as a radical 
scavenger and hydroperoxide decomposer. It transforms the hydroperoxide 
formed throughout the oxidation process to non-radical products, thus 
avoiding chain propagation. The mechanism of oxidation inhibition by 
ZDDC consists of complex reactions between alkylperoxy radicals, organic 
hydroperoxides and intermediate decomposition products of initial 
compounds [13]. 
The bio-lubricant recorded a longer time to fully oxidize when 
induced with ZDDP additives. When the palm oil bio-lubricants were added 
with 1.2wt% concentration of ZDDP additives, the sample showed an 
increment of oxidation time to 111 minutes. Through further addition of 
ZDDP additives at 1.6wt% concentration, the palm oil bio-lubricant 
completely oxidized at 124 minutes. With the addition of ZDDP additives at 
Oxidation Stability Comparison between Zinc Dialkyldithiophosphatel  
 
27 
 
 
2.0wt% concentration, the samples of newly developed bio-lubricant shows 
an increment of time which was found to be oxidized at 128 minutes. It can 
be observed that the ZDDP samples are more effective in slowing down the 
oxidation reaction as it took longer time for the samples to be fully oxidized 
comparing with the samples added with ZDDC. This is because ZDDP has a 
presence of sulphides, where these sulphides decelerated the initiation of new 
radical chain. When hydroperoxides react with hyroperoxide decomposer 
with sulfides, it will produce alcohols and sulfoxides. This enables the 
sulfoxides to react much further and eliminate additional equivalents of 
hydroperoxides in complex chain of reaction. Therefore the oxidation process 
can be slowed down [14]. The oxidation stability of vegetable oils are 
improved with the presence of additives. The introduction of antioxidant is 
capable to resolve the oxidative stability drawbacks in vegetable based oil 
[7]. This also supported by Hu et al., that ZDDP is an effective anti-oxidant 
additives [15]. 
 
 
Figure1: Oxidation Time of New Bio-Lubricant 
 
Conclusions 
 
Oxidation in lubricant oil shall be suppressed in order to increase the 
performance of a lubricant. In this study the addition of ZDDP and ZDDC 
has increased the oxidation time of palm oil based bio-lubricant. However, 
this study discovered that the addition of ZDDP at 2 wt% displayed a better 
oxidation time compared to other concentrations of additives added to the 
commercialized palm oil. 
 
 
0
20
40
60
80
100
120
140
Pure
Palm
Oil
1.2wt%
ZDDC
1.6wt%
ZDDC
2.0wt%
ZDDC
1.2wt%
ZDDP
1.6wt%
ZDDP
2.0wt%
ZDDP
O
x
id
at
io
n
, 
(m
in
u
te
s)
 
Muhamad Azwar bin Azhari  et al. 
 
28 
 
 
Acknowledgement 
 
The author would like to acknowledge the Malaysian Ministry of Higher 
Education (RAGS/ 2015/FTK/TK03/B00116) and Universiti Teknikal 
Malaysia Melaka for the support and funding throughout this study. 
 
References 
 
[1] Bannister, K, “Lubrication for Industry,” New York Industrial Press 
(1996). 
[2] Kucera, M. and Rousek, M, “Determination of the Oxidative stability of 
Vegetable Oil – Based Lubricants,” Stanovenie Oxidacnej Stability 
Maziv Na Rastlinnej Baze (2), 101-109 (2011). 
[3] Mahipal, D., Krishnanunni, P., Mohammed, R.P. and Tonck, A, 
“Analysis of lubrication properties of zinc-dialkyl-dithio-phosphate 
(ZDDP) additives on Karanja oil (Pongamia pinnatta) as a green 
lubricant,” International Journal of Engineering Research 5013 (3), 494-
496 (2014). 
[4] Mobarak, H. M., Niza Mohamad, E., Masjuki, H.H., Kalam, M. A., Al 
Mahmud, K. A. H., Habibullah, M., & Ashraful, A. M., “The prospects 
of biolubricants as alternatives in automotive applications,” Renewable 
and Sustainable Energy Review 33, 34-43 (2014). 
[5] Cheenkachorn, K. and Udornthep, I, “A Development of Four-stroke 
Engine Oil using Palm Oil as a Base Stock,” Joint International 
Conference on Sustainable Energy and Environment 26 (1), 24-27 
(2006). 
[6] Azhari, M.A., Saroji, M.F.H.M. and Latif, M.F.A., “Comparison of 
Tribological Properties Between Canola Oil + ZDDP and SAE 40 
Lubricants,” Jurnal of Engineering and Applied Science II (10), 2126-
2129(2016). 
[7] Azhari, M.A., Mat, L.H. and Hafiz Harun, M., “A Review Addition of 
Molybdenum Compounds Into Zinc Induced Bio-Lubricants As 
Lubricant Substitution,” Jurnal of Engineering and Applied Science II 
(9), 2050-2053 (2016). 
[8] Du, D., Kim, S.S., Moon, W.S., Jin, S.B. and Kwon, W.S., “Oxidation 
performance of oils containing ZnDTC, ZnDDP and their mixture after 
oxidation test by PDSC,” Thermochimica Acta 407 (1-2), 17-23 (2003). 
[9] Hamrock, B.J., Schmid, S.R. and Jacobson, B.O., “Fundamentals of 
Fluid Film Lubrification Second Edition,” Marcel Dekker, Inc (2004). 
[10] Aluyor, E. and Ori-Jesu, M., “The use of antioxidants in vegetable oils,” 
African Journal of Biotechnology 7 (25), 4836-4842 (2008). 
[11] Azhari, M.A., Suffian, Q.N., Saroji, M.F.H., M. and Nuri, N.R.M., 
“Addition of ZDDP in corn oil as lubricant physical property improver,” 
Oxidation Stability Comparison between Zinc Dialkyldithiophosphatel  
 
29 
 
 
Proceedings od Malaysia Internatioanal Tribology Conference, 213-214 
(2015) 
[12] Rudnick, L.R., “Lubricant Additives,” Journal of Chemical Information 
and Modelling (2013). 
[13] Erhan, S.Z., Sharma, B.K. and Perez, J.M., “Oxidation and low 
temperature stability of vegetable oil-based lubricants,” Industrial Crops 
and Products 24 (3), 292-299 (2006). 
 


Oxidation Stability Comparison between Zinc Dialkyldithiophosphate and Zinc Diamyldithiocarbarmate Induced Palm Oil Bio-lubricants / Muhamad Azwar Azhari ...[et al.]

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Oxidation Stability Comparison between Zinc Dialkyldithiophosphate and Zinc Diamyldithiocarbarmate Induced Palm Oil Bio-lubricants / Muhamad Azwar Azhari ...[et al.]

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