Tribological behavior as lubricant additive and physiochemical characterization of Jatropha oil blends

This investigation reports on the effect of Jatropha oil doped with lube oil on tribological characteristics of Al-7%Si alloy. The factors involved were Jatropha oil percentages, sliding velocities and load which was optimized for weight loss, friction coefficient and specific wear rate characteristics. The conventional lubricant was SAE 40. It is observed that the Jatropha oil percentage factor had significant influence on the weight loss, friction coefficient and wear rate of the pin. The optimum result was A2 B3 C1 for pin weight loss, friction coefficient and wear rate. From the experimental result, it is found that the wear scar diameter increases with the increase of load for lube oil and reduced by addition of percentage of Jatropha oil. Flash temperature parameter was also studied in this experiment and results show that 15% addition of Jatropha oil would result in less possibility to film breakdown. The overall results of this experiment reveal that the addition of 15% Jatropha oil with base lubricant produces better performance and anti-wear characteristics. This blend can be used as lubricant oil which is environment friendly in nature and would help to reduce petroleum based lubricant substantially.


INTRODUCTION
acid composition resulting into formation of thick film Around the globe, there are challenges for the better anti wear properties [9][10]. industries involved in manufacturing petroleum based There are some drawbacks of vegetable oil based lubricant products to face government regulations and lubricants that they have lower thermal/oxidative stability, also meet latest technological changes to make cleaner higher flash point and high temperature operability leads environment and reduce pollution caused by them [1][2].
to higher coefficient of friction [11]. To overcome these There are various lubricants available around the world limitations, several researches have been carried out. which includes synthetic oil, mineral oil and vegetable oil.
Oxidation stability and low pour point can be modified by Lubricants available in the market i.e. mineral oil are partially adding additives and using N-Phenyl-alphaderived from crude petroleum oils and are not feasible naphthylamine (Am2) as antioxidant to improve oxidation with the environment as they are non-biodegradable and stability [12][13][14]. Moreover, transesterification or toxic [3][4]. Also, the disposal of mineral caused pollution epoxidation are the solutions to meliorate oxidation to the aquatic and terrestrial ecosystems and combustion stability at low temperature [15][16]. To make vegetable oil of the mineral oil leads to emission of metal traces like, based lubricant sustainable, there is a need to improve calcium, zinc, magnesium and phosphorous and nano-their narrow range of viscosities [17]. Viscosity is one of particles [5][6]. Vegetable oil can be used as an alternative the significant factor in determining coefficient of friction to petroleum based mineral oil as it possesses several between the sliding surfaces as it act as protective film advantages which include biodegradability, lower toxicity, between the surfaces in contact to protect them from lowervolatility and higher lubricity [7][8]. They have wear. To do so, viscosity modifiers can also be used triacylglycerol structure which contains long, polar fatty which are friendly with environment. Oleogels based on between the metal to metal contacts and impart them conventional, bio-based lubricant and ethylene-vinyl blended lubricants, Sliding Velocity and load using acetate (EVA) copolymer have been developed. It has taguchi method to determine influence of the control been observed that EVA can be used as an effective parameter on the minimum material weight loss, friction thickener agent to make vegetable oil as Bio-based and specific wear rate. lubricant [18]. Viscosity of bio-based lubricant can also be increased by using ethylene-vinyl acetate and styrene-Experimental Details butadiene-styrene copolymers as they increase some used for polishing disc after each experiment. After It has been concluded from the above literature that completion of each test, pin and disc specimen was very limited work has been done based on bio-based cleaned ultrasonically with ethyl alcohol and stored in lubricants. The objective of this study is to optimize vacuum oven furnace to avoid corrosion of the material. various control parameters which include jatropha oil For the examination of the worn surfaces, trinocular stereo  zoom microscope was used. Mean average value was used after completing each experiment three times to maintain accuracy in the results.

Viscosity and Total Acid Number Test (TAN):
Anton paar viscosity meter and TAN/TBN analyzers were used for investigating degradation of the lubricant. The kinematic viscosity was measured at 40°C and 100°C according to ASTM D445 standard. For the TAN analysis, c(KOH)=0.2 mol/l in isopropanol as the titrant was used according to ASTM D664-81 standard.

Wear Scar Diameter:
The trinoculur stereo zoom microscope was used to calculate the wear scar diameter of the pin. Suitable magnificationlens was chosen and the focus was adjusted until clear image is shown on the computer screen. After that, view 7 software available in the computer was used for the measurement of wear scar diameter.

Flash Temperature Parameter: Flash Temperature
Parameter is a single number used to express the critical flash temperature above which givenlubricant will fail under given conditions [31]. The following formula has been used for Flash temperature parameter analysis: where; W = load in N, d = mean wear scar diameter (WSD) in mm at this load

Design of Experiments Employing Taguchi Method:
Taguchi method developed orthogonal array to study the effect of control factors involved and to minimize number of experiments. The experimental results obtained are then converted to signal to noise ratio (S/N) which measure quality characteristics to understand that the results are deviating from or nearer to the obtained results. There are three categories involved for quality characteristics to analyze S/N ratio. These are: the smaller the better; the larger the better; the nominal the better. These can be calculated according to the below mentioned equations. The-smaller-the-better: where, 'n' indicates number of replications and 'y' indicates the observed response value. It is employed where smaller value is desired. The-nominal-the-better: where, 'µ' indicates mean and ' ' indicates the variance. It is employed where nominal or variation is minimum. The-higher-the-better: where, 'n' indicates number of replications and 'y' indicates the observed response value.

Process Parameters:
In this experiment three control factors with three levels were selected. The details of the factors to be considered and level assigned with them are designated in Table 2. Level indicates the values taken during plan of experiments. Minitab 16 softwarewas used for the selection of the orthogonal array. L9 orthogonal array was selected and details of the experiments to be investigated is shown in Table 3. Three columnswere considered and each consists of three levels.
The plan of experiments includes 9 row experiments in which first column was assigned to the jatropha oil blended lubricants (%), second to the sliding velocity (rpm) and the third to the load (N). Responses taken RESULTS AND DISCUSSIONS during the experiment were pin weight loss, friction coefficient (µ) and wear rate (mm2/N).
Prediction of Control Factor Effects: Table 4 shows the ANOVA: ANOVA stands for analysis of variance and it and specific wear rate at different levels of control factors is a statistical technique which control factors involved considered. Responses of each control factors on pin and used to determine the percentage contribution of weight loss, friction coefficient and wear rate were each control factors to reveal the their effect on the determined and analyzed using S/N ratio table. Table 5-7 quality characteristics. The increase in S/N ratio indicates S/N response tables for pin weight loss, friction determines the increase in control factor. It can be used to coefficient and wear rate. From table 5, it can be revealed investigate the different factors including degree of that minimum pin weight loss was observed at Level 2 of freedom (DF), Sequential sum of square (Seq SS), jatropha oil blends (%) i.e. JB 15, level 3 of sliding velocity Adjusted Sum of square (Adj SS), Sequential mean square i.e. 3.8 m/s and level 1 of Load i.e. 50 N. According to the (Seq MS) and last column indicates the p value for each rank, Jatropha oil Blends (%) has strong influence for this control parameters. The row having least p value was response. 15% contamination of jatropha oil with lubricant contributed more to the response involved and the provides less pin weight loss as it will act as barrier to the control factor having maximum value than the F value is metals in contact during tribo test. From table 6, it is insignificant.
observed that minimum friction coefficient was at level 2 experimental output for pin weight loss, friction coefficient     lubricants. These fatty acid compositions consists of According to the rank, Jatropha oil Blends (%) has strong molecules which form a long chain covalently bonded influence for this response and after that load influences hydrocarbon chain and act as an efficient barrier for friction coefficient. Table 7 also provides the same protecting sliding surfaces contact and provides better combination of the levels as stated above but specific wear protection than conventional hydrocarbon based wear rate was influenced more by applied load and then lubricants. Esters have polar functional group which jatropha oil blends (%).
provides better affinity to metal surface and contributed Fig. 1: a-c shows the main effect plot for S/N ratios. towards formation of protective layer between metal From these graphs, optimum results for the factors surfaces. Minimum pin weight loss, friction coefficient included could be determined. and wear rate were observed at higher sliding velocity and Figure 1 a-c shows the main effect plot for S/N ratios. lower load. In comparison to sliding velocity, load had Among the JB 0, JB 15 and JB 30, JB 15 (15% blend with significant effect on the responses considered during the conventional lubricant) shows minimum pin weight loss, analysis. With increase of load, friction force increases friction coefficient and wear rate as it provides better which results in more pin weight loss, friction protective film between metal to metal contact in coefficient and specific wear rate. JB 15 shows better comparison to JB 0 and JB 30. This could be attributed to result with increase of sliding velocity due to higher and first level of Load applied i.e. 50 N was considered as better lubricity at lower sliding velocity. Another reason better control factors. behind the better results at higher sliding velocity is the increase of temperature which reduces viscosity making ANOVA Analysis: Table 8-10 shows the ANOVA table  it responsible for the formation of excellent tribo layer. for pin weight loss, friction coefficient and specific wear Aluminium has an inherent property of forming an oxide rate. From Table 8, the jatropha oil blends percentage layer on its outer periphery. When sliding at high (57.5%) and load (27.9%) had significant influence on the velocity, the temperature increases over the contact pin weight loss and the contribution of Sliding Velocity surface, making the material to oxidize. This phenomena (6.1%) was least as compare to other two control factors. leads to the transferring of materials, forming The reason behind significant influences of the jatropha Mechanically Mixed Layer (MML), also called tribo layer. oil percentage and load was stated earlier. Among the As the velocity increases, this tribo layer will act as a interactions, sliding velocity with load (10.7%) had barrier or lubricant between the two surfaces decreasing significant influence on pin weight loss. It can be the coefficint of friction, wear rate and pin weight loss observed from Table 9 that jatopha oil percentages [32]. Optimum results for the control factors influenced more the friction coefficient as compared to considered were determined from Main effect plots for load and sliding velocity. Frictional forces had significant pin weight loss, friction coefficient and specific wear rate.
influence on the friction coefficient according to the The optimum result for all the responses i.e pin weight below formulaloss, friction coefficient and wear rate was A2B3C1. This means that the level second of Jongamia oil blends µ = F/N (5)   indicates that almost all the normal probability plot follow From Table 10, the jatropha oil percentage (48%) and a straight line pattern. sliding velocity (15.1%) had significant influence on the specific wear rate and the contribution of load (11.6%) Correlation: Linear regression equation was used to was least as compare to other two control factors. Among correlate control factors (Jatropha oil Percentages, Sliding the interactions, sliding velocity with load influenced Velocity and load) and the Responses (Pin weight loss, more followed by jatropha oil with load (10.9%).
Friction coefficient and wear rate).     An experiment were conducted for the new set of the control factors and the output was compared with the output obtained from the predicted equation as shown in Table 11.
The following equation was used to obtain confidence interval for the predicted mean of the confirmation test [33]. The 95% confidence interval for the predicted mean of the confirmation test was shown in Table 12.
Wear Scar Diameter Analysis: Figure 5 shows the wear scar diameter of Al-7% Si alloy pin with jatropha oil blends percentage at different load and sliding velocity. Wear scar diameter increases with increase of load and maximum wear scar diameter was observed at 150 N load for each blend considered. This is due to increase in friction force applied with increase of load. Minimum wear scar diameter was found at 3.8 m/s sliding velocity and maximum at 1.3 m/s sliding velocity. It reduces with  Higher flash temperature ability of JB 15 makes this blend acting as lubricant which was formed due to increase of more compatible at high temperature. The lowest value of temperature with increase of sliding velocity. JB 15 shows FTP was found to be atJPB 30. minimum wear scar diameter among all the jatropha oil While for 3.8 m/s sliding velocity test, figure shows blends as it provides better protective layer between metal 15% of jatropha oil was the highest value of FTP. Means, to metal contacts.
15% of jatropha oil was the best additive for fresh lube oil Flash Temperature Parameter Analysis: Figure 6. Shows phenomena. The lowest value was occurred at 30% of the effect of jatropha oil blend on flash temperature jatropha oil. That means, both 30% contamination of parameter at different load and sliding velocity. Generally jatropha with lubeoil was making much wear on metal by observation, the trend of flash temperature parameter surface in contact at 40°C. is increased when the load is increased from 50 N to 150 N due to increase in frictional force with increase of load.
Degradation of Lubricant: Viscosity is a significant factor For 1.3 m/s Sliding velocity, the lubricant performance was in determining the degradation of lubricant as it provides improved by 15% contamination of jatropha oil with a protective film thickness between the surfaces in conventional lubricant as viscosity provides protective contact and protect wear of metal surfaces during sliding. film layer with increase of sliding velocity. JB 15 shows It is also contribute towards identification of oil grades higher flash temperature parameter compared to other and for monitoring the change in range of viscosity while percentage of contamination. It proves that JB 15% was the vehicle is in service. The deterioration of used oil can potential anti-wear additive for conventional lubricant. for jatropha Oil at 15% (JB 15). As the JB 15 makes a thick This contributes towards increment of the length of film between the sliding surfaces in contact and protect molecular chainwhich results into increased viscosity of from wear in comparison to other contaminated jatropha the used oil. From the figure, it shows that for the Oil blends i.e.JB 30 and JB 0. contamination of jatropha oil with lube oil, the highest value wasstated for 15%. Means, 15% of jatropha oil was CONCLUSION the best contamination with lube oil in order to maintain the anti-wearcharacteristic such as kinematic viscosity.
The taguchi method was applied to optimize the pin The figure also showed that normally the values of weight loss, friction coefficient and wear rate at different kinematic viscosity forall samples at 40°C were higher control factors. The results are summarized as follows: than 100 centistokes (cSt.). It stated that basically the Taguchi method was suitable to optimize the kinematic viscosity of thesesamples was lower than the tribological behavior of different jatropha oil blends samples at 40°Cwhich is about below 20 cSt. The lower at various sliding velocities and loads. value of kinematic viscositywas affected by the The optimum condition for the pin weight loss, temperature. With higher the temperature, the kinematic friction coefficient and wear rate was A2B3C1. It can viscosity will be lower due to theliquidity of the samples be revealed at level 2 of first control factor (JB 15), lubricant.
third level of sliding velocity (3.8m/s) and third control factor was better at first level (50N). Also as ACKNOWLEDGEMENT a result of the design method ANOVA, the factor Jatropha Oil blends percentage has the maximum contribution in controlling the friction and wear behavior of Pin against the disk. The pin weight loss was influenced primarily by jatropha oil blend percentage, the applied load and sliding velocity. The friction coefficient was influenced maximum byjatropha oil blend, Load and then sliding velocity. The specific wear rate was influenced primarily by jatropha oil blend percentage, sliding velocity and the applied load. Generally, it was observed that the interactions between the control factors have significant influences on the pin weight loss, friction and wear rate of Aluminium alloy pin. Deviations between actual and predicted S/N ratios for pin weight loss, friction coefficient and wear rate are negligibly small with 95% confidencelevel. The wear scar diameter (WSD) increases with increase of load and decreases with increase of sliding velocity. That means, at lower loads the WSD under jatrophacontaminated lubricant are lower, where at higher loads, the WSD are higher. The results shows that the contaminations of lube oil at 30% of jatropha oil at 1.3 m/s Sliding Velocity and 150 N Load give higher WSD. At 15% of jatropha oil, the value of WSD stated that it was the lowest which means 15% of Jatropha oil got the lesser scars and made it the best anti-wear. The higher value of flash temperature parameter (FTP) clearly observed when 15% of jatropha oil was used. The 15% of jatropha oil improves the lubricant (SAE 40) performance, indicating less possibility of lubricant film breakdown. From the observations on worn surfaces of these specimens, 15% of jatropha oil contaminated conventional lubricant shows better anti-wear lubricant properties than others. For the contamination of jatropha oil with lube oil, the highest value of kinematic viscosity was stated for 15% at both two temperatures tested (40°C and 100°C).
According to the experimental result, 15% of jatrophaoil contaminated with the base lubricant showed better performance in terms of wear and friction characteristics and can be the alternative lubricant for the automotive application.
The author would like to thank the department of mechanical engineering, college of engineering studies, University of Petroleum and Energy Studies, Dehradun, India to make this study possible.