Synthesis, Characterization, and Performance Evaluation of SomeMultifunctional Lube Oil AdditivesPranab Ghosh* and Moumita Das

Natural Product and Polymer Chemistry Laboratory Department of Chemistry, University of North Bengal, Darjeeling-734013, India

*S Supporting Information

ABSTRACT: Eight polymers (two homopolymers and sixcopolymers with 1-decene) of isodecyl acrylate and isooctylacrylate were synthesized using benzoyl peroxide as initiatorand characterized by spectral analysis, viscometric, andthermogravimetric measurements. Intrinsic viscosity obtainedfrom the viscometric method was used to determine theviscometric molecular weight of the polymers. Pour point (PP)and viscosity index (VI) of the additive-doped base oils wereevaluated to check the efficiency of the polymers as pour pointdepressant (PPD) and viscosity index improver (VII),respectively. Analysis of different properties indicates that the isooctyl acrylate polymers have better lube oil additive propertythan that of isodecyl acrylate polymers. VI and PP values of the polymers doped in base oils depend on the nature of mineral baseoils, polymer type, and also on the concentration of the additives.

■ INTRODUCTION

Base oil, which is also known as lubricant base oil, is the basicbuilding block of a lubricant. The rheological properties such asfluidity of the oil at low temperature, viscosity, and variation ofviscosity with temperature govern the performance of lubricantbase oils. To have effective performance at low as well as at hightemperatures, an engine lubricant should be fluid at lowtemperature and should have minimum variations of itsviscosity with temperature. To improve the quality, lube oilalways contains different types of additives or additives aremixed to the lube oil to impart a new and desirable propertywhich was not originally present in the oil. Sometimes additivesamplify the property already present to some degree in the oil.1

The quantity and quality of the additives depend on the natureof the base oil and also on the purpose of their use. Types ofadditives are antioxidants, detergents and dispersants, corrosioninhibitors, viscosity index improvers (VIIs) and pour pointdepressants (PPDs), etc. Of them VIIs and PPDs are the veryimportant ingredients in modern lubricants.PPDs2 are chemical additives which are used to transport

lube oils at low-temperature areas. They are added to maintainoil flow ability below a certain temperature which is termed aspour point (PP) and defined as the temperature at which theflow ability of oil totally ceases due to wax crystal latticeformation. These are basically polymeric compounds made ofhydrocarbon chains. At the time when the temperaturebecomes low and the oil cools down, then during thedevelopment of wax crystal network, the hydrocarbon chainsbecome inserted in the lattice and thus inhibit wax crystalformation or modify the wax crystal network. So they are alsoknown as wax crystal modifiers. Among the different kinds ofpolymers,3 acrylic and methacrylic ester polymers are very

efficient as crude oil wax crystal modifiers and wax depositioninhibitors.4,5

Again, viscosity is a very important property of a lubricant.6,7

The viscosity of a liquid is a measure of its resistance to flow.High viscosity oil is less fluid than the one of low viscosity. Athigher temperatures, the oil tend to thin out and flow morereadily and vice versa. The change in viscosity with the variationof temperature is expressed by a parameter known as viscosityindex (VI). Higher VI of oil means the viscosity of the oil doesnot vary much with the variation of temperature. VIIs8 orviscosity modifiers (VMs) are added to the lubricating oil toimprove the VI of the oil.To determine the molecular weight of the polymers,

viscometry is employed as the procedure is very easy to carryout and the apparatus used is very simple. After evaluating thevalue of intrinsic viscosity, [η], the molecular weight (M) of thepolymers can be calculated from Mark−Houwink equation, asaccording to the equation there is a relation between [η] andMof the polymer:

η = KM[ ] a

In this equation, K and a are the Mark−Houwink parametersand the molecular weight obtained is the viscosity averagemolecular weight. The value of K and a depend on a specificpolymer−solvent combination and to get the exact molecularweight of the polymer, these parameters are to be knownexactly. So, for a new polymer it is not possible to get theaccurate molecular weight, but an idea of whether the molecular

Received: April 28, 2012Accepted: February 14, 2013Published: February 25, 2013

Article

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weight value is low or high can be drawn by using these valuesof similar types of polymers. Also, there are some relations, forexample, Huggins, Kraemer, Martin, Schulz−Blaschke, Solo-mon−Ciuta and Deb−Chatterjee equations from which thevalue of [η] of a polymer solution in dilute condition at aparticular temperature is determined. Among the above-mentioned six equations, the [η] value is determined bygraphic extrapolation from the first four and by single pointdetermination from the remaining two.9−11

The results of our analysis toward the synthesis of differenttypes of the polymers, characterization of them by thermog-ravimetric, spectral, and viscometric analysis and also evaluationof the performance of the polymeric additives as PPDs andVIIs, based on long chain acrylates, such as homopolymer ofisodecylacrylate (HIDA) or poly(isodecylacrylate) and iso-decylacrylate (IDA) + 1-decene copolymers in comparison tothe homopolymer of isooctylacrylate (HIOA) or poly-(isooctylacrylate) and isooctylacrylate (IOA) + 1-decenecopolymers prepared under identical conditions, will bediscussed in this paper. Comparison of different propertiesamong the copolymers is also presented here.

■ EXPERIMENTAL SECTIONMaterials. Details of the materials used and their

specification are tabulated in Table 1.

Esterification. Esterification of acrylic acid with isodecylalcohol and 2-ethylhexanol (isooctanol) to prepare isodecylacrylate (IDA) and isooctyl acrylate (IOA), respectively, wascarried out in toluene taking H2SO4 as a catalyst andhydroquinone as polymerization inhibitor and following theprocess as reported earlier.12

Purification of Prepared Esters. All of the prepared esterswere purified by the process as reported earlier.12

Preparation of Copolymer and Homopolymer. Homo-polymer of IDA and IOA (HIDA and HIOA, respectively) wereprepared and in the preparation of IDA + 1-decene and IOA +1-decene copolymers, different mole fractions of 1-decene wereused (Table 2). The polymerization was carried out in toluenesolvent using BZP as initiator and by following the method asreported elsewhere.12

■ MEASUREMENTSSpectroscopic Measurements. Shimadzu FT-IR 8300

spectrophotometer was used to record the IR spectra of thesamples using KBr cells (0.1 mm) at room temperature. 1H and13C NMR spectra were recorded in CDCl3 in a 300 MHzBruker Avance FT-NMR spectrometer using 5 mm BBO probe.Tetramethylsilane (TMS) was used as reference material.

Viscometric Measurements. For the determination ofviscometric properties of the polymers in toluene solution, theexperiment was carried out at 313 K, using an Ubbelohde OBviscometer. Time flow of eight different concentrated solutionsof each of the polymer samples was taken. A chronometer wasused for manual determination of the time flow of the solution.In the single point determination method, the lowest solutionconcentration value was chosen for calculation. For thedetermination of viscosity-average molecular weight (M), theMark−Houwink constants K = 0.00387 dL·g−1 and a = 0.725were employed.13

The data obtained from viscometric measurements werecompared in reference to known solutions and the uncertaintywas found to be about 0.17 %. During the measurementsadequate precautions were taken regarding the loss due tosolvent evaporation.

Thermogravimetric Analysis (TGA). TGA was carried outon a mettler TA-3000 system in air at a heating rate of 10K·min−1. During the experiment, the temperature varied withinthe range ± 10 K and the uncertainty in determining PWL waswithin the range ± 1.3 %.

Evaluation of PP of the Additives in Lube Oil. The PPof the prepared polymers in two base oils (BO1 and BO2) wastested according to the ASTM D97-09 method on a Cloud andPour Point Tester model WIL-471(India). Different massfractions ranging from 0.010 to 0.030 were used to check howthe PP of lube oils varies with additive concentration. Anaverage of three experimental data taken under identicalcondition was recorded. During the experiment, the temper-ature varied within the range ± 0.1°.

Evaluation of Viscosity Index of the PreparedAdditives in Lube Oil. The viscosity index of the preparedpolymers was evaluated in two base oils according to the ASTMD2270 method and by following the equations as reportedelsewhere.14 Polymer solutions of different mass fractionsranging from 0.010 to 0.060 were prepared to investigate theviscosity modifier properties of the polymers with the change inits concentration. The dynamic viscosity of the polymer

Table 1. Specification of Chemicals

chemical name sourcemole fraction

puritypurificationmethod

toluene Merck Specialties Pvt.Ltd.

0.995 distillation

hydroquinone Merck Specialties Pvt.Ltd.

0.990 recrystallization

H2SO4a Merck Specialties Pvt.

Ltd.acrylic acid SRL Pvt. Ltd. 0.990 distillationisodecanol SRL Pvt. Ltd. 0.980 distillationhexane S. D. Fine-Chem Ltd. 0.995 distillation1-decene Across Organics. 0.950 distillationmethanol Thomas Baker Pvt.

Ltd.0.980 distillation

benzoylperoxide

LOBA chemicals 0.980 recrystallization

2-ethylhexanol LOBA chemicals 0.990 distillationaH2SO4 was used as received.

Table 2. Specification of Prepared Polymer Samplesa

x2b

sample by NMR method by IR method purification method

P-1 0.0000 0.0000 reprecipitationP-2 0.0144 0.0147 reprecipitationP-3 0.0427 0.0435 reprecipitationP-4 0.0686 0.0698 reprecipitationP-5 0.0000 0.0000 reprecipitationP-6 0.0116 0.0121 reprecipitationP-7 0.0364 0.0372 reprecipitationP-8 0.0613 0.0622 reprecipitation

aP-1: homopolymer of isodecyl acrylate (HIDA), P-2 to P-4:copolymer of IDA + different mole fractions of 1-decene, P-5:homopolymer of isooctyl acrylate (HIOA), P-6 to P-8: copolymer ofIOA + different mole fractions of 1-decene. bx2 is the mole fraction of1-decene in the copolymers.

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samples was measured at 313 K and 373 K. Each measurementwas repeated thrice and the uncertainty was found to be about0.17 %.Properties of Base Oils. Physical properties of the base oils

were tabulated in Table 4.

■ RESULTS AND DISCUSSIONSpectroscopic Data. In its IR spectrum the homopolymer

of isodecyl acrylate (HIDA) exhibited absorption band at 1732cm−1 for the ester carbonyl stretching vibration along withother peaks at (1456.2, 1379, 1260, and 1166.9) cm−1 (COstretching vibration) and at 750 cm−1 and 710 cm−1 (bendingof C−H bond). In its 1H NMR spectra, poly(isodecylacrylate)showed a broad singlet centered at 4.02 ppm due to the protonof the −OCH2 group; another broad singlet centered at 0.86ppm was due to methyls of isodecyl chain. The protondecoupled 13C NMR of the above sample was in completeagreement with the homopolymer which shows the presence ofester carbonyl group at 174 ppm and absence of any sp2 carbonin the range 130 ppm to 150 ppm.The formation of the copolymer was confirmed by

spectroscopic data. In its FT-IR spectra, the copolymer showeda broad peak ranging from 1732 cm−1 to 1737 cm−1 for estercarbonyl along with other peaks at 2928.7 cm−1, 2871.8 cm−1,1462.9 cm−1 and a band at 1164 cm−1 for stretching andbending vibration of −CH2 groups. In the 1H NMR spectra ofthe copolymer, a broad singlet at 4.05 ppm was due to theprotons of −OCH2 group. Methyls of the isodecyl chainappeared between 0.81 ppm to 0.86 ppm and the absence ofsinglets between 5 ppm and 6 ppm indicated the absence of anysp2 proton in the prepared copolymer. In its 13C NMRspectrum, a peak at 174 ppm showed the presence of carbonylcarbon and the absence of peak between 130 ppm and 150 ppmindicated the absence of any sp2 carbon.

IR spectrum of the poly(isooctylacrylate) exhibited absorp-tion at 1731 cm−1 for the stretching vibration of ester carbonyl.Peaks at 1260 cm−1 and at 1164.9 cm−1 were due to the C−O(ester bond) stretching vibration and the absorption peaks at(961, 775 and 720) cm−1 were due to the bending vibration ofC−H bond. A broad peak ranging from (2929 to 2950) cm−1

indicated the presence of C−H stretching vibration. 1H and 13CNMR was also in complete agreement with the homopolymer.In its 1H NMR spectra, the homopolymer of IOA showed a

broad singlet centered at 4.01 ppm for the protons of the−OCH2 group; a broad singlet at 0.89 ppm was for the methylgroups of isooctyl chain. The proton decoupled 13C NMR ofthe above sample shows no peak between 130 and 150 ppmwhich indicated the absence of any sp2 carbon. The presence ofthe ester carbonyl group was indicated by the peak at 170 ppm.The formation of the copolymer of IOA and 1-decene was

indicated by the absence of a peak between 5 ppm and 6 ppmdue to sp2 hydrogen and that between 130 ppm and 150) ppmdue to sp2 carbon in its 1H and 13C NMR, respectively.The extent of incorporation of 1-decene in the copolymer

composition, as determined from IR and FT-NMR methods,12

increases with increasing 1-decene concentration in the feed.Thermogravimetric Analysis. The analysis reveals that

the IOA polymers are thermally more stable than the IDApolymers. Again, Figure 1 indicates, among all the polymers of

IDA, the copolymer with maximum of 1-decene (P-4) contentis the most stable while Figure 2 shows that the homopolymerof IOA (P-5) is the most stable among the IOA polymers.

Viscometric Analysis. By using the above-mentioned sixequations, viscometric data (ηr = relative viscosity, ηsp = specificviscosity, [η] = intrinsic viscosity, etc.) were obtained. Plot oflog ηsp versus log C[η], for all samples (Figure 3), showslinearity in all cases which indicates that while the experimentswere performed Newtonian flow was there in the solution.9,10

In Table 3, the intrinsic viscosities ([η]) of all samplesdetermined by using the above-mentioned equations areshown. In both single point determination and the graphicextrapolation method, the SB equation is applied.13 For manypolymer−solvent systems, ksb, used in SB equation is found tobe very close to 0.28 and so the same value is used for the SBsingle point determination method. Comparison among all the

Table 3. Intrinsic Viscosity [η] Values for All PreparedPolymer Samples Calculated by Using Different Equationsa

sample [η]hb [η]k

b [η]mb [η]sb

b [η]sbc [η]sc

c [η]dcc

P-1 3.77 3.85 3.88 3.95 4.02 3.98 4.12P-2 3.70 3.81 3.82 3.90 4.00 3.96 4.10P-3 3.64 3.76 3.77 3.86 3.93 3.90 4.02P-4 3.54 3.60 3.62 3.69 3.70 3.66 3.79P-5 6.37 6.50 6.77 7.08 6.63 6.62 6.99P-6 7.29 7.31 7.77 8.13 7.38 7.39 7.85P-7 7.58 7.68 8.17 8.60 7.82 7.84 8.44P-8 7.75 8.13 8.61 9.19 8.30 8.36 8.94

aSubscripts h, k, m, sb, sc, and dc refer to Huggins, Kraemer, Martin,Schulz−Blaschke, Solomon-Ciuta and Deb-Chatterjee equations,respectively. bExtrapolation of graph. c-Single point determination(ksb = 0.28). [η] is measured in dL·g−1. The uncertainty in determining[η] is within the range ± 0.14 %.

Table 4. Base Oil Properties

base oils

properties BO1 BO2

density (kg·m−3) at 313 K 836.98 868.03viscosity at 313 K in Pa·s 5.97 × 10−3 20.31 × 10−3

viscosity at 373 K in Pa·s 1.48 × 10−3 3.25 × 10−3

cloud point/°C −10 −8PP/°C −3 −6

Figure 1. Plot of PWL vs T for the polymers of isodecyl acrylate,where PWL is the percent weight loss of the polymer and T istemperature in Kelvin: ○, P-1; □, P-2; Δ, P-3; ■, P-4.

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polymers of IDA indicated that, the homopolymer (HIDA, P-1) has greater intrinsic viscosity ([η]) values (corresponding toall the six equations mentioned) than the copolymers with 1-decene and for the copolymers, the [η] values decrease withincreasing concentration of 1-decene in the feed. This indicateshomopolymer chains are more extended in the solution thanthe copolymers. For the polymers of IOA, the [η] values for thehomopolymer are lower than the copolymers and comparisonamong the [η] values of the copolymers showed that the [η]

values increase with increasing concentration of 1-decene in thefeed. So, there is a less extended conformation of thehomopolymer chain compared to the copolymers and in thecase of copolymers, stretching of the chain is more and morewith increasing percentage of 1-decene in the feed. Also, thecomparison among the [η] values of IOA and IDA polymersshows that the values of IOA polymers are greater than that ofIDA polymers which indicates more solute−solvent interactionfor IOA polymers than IDA polymers in toluene solution.From the viscometric constant values (kh, kk, km, and ksb) as

obtained from the four equations (Huggins, Kraemer, Martin,and Schulz-Blaschke, respectively) of the graphic extrapolationmethod, it may be concluded that there exists good solvation ofthe polymer in toluene and thus the extended chain orientationmay also be predicted for all the polymer solutions.15 The kh +kk values also point toward the same conclusion.15 Percentualdifference (Δη %) of [η] values of all the polymers takingHuggins equation as reference and determined through all theequations shows that the range for IDA polymers was narrowcompared to the range for IOA polymers.The viscometric molecular weight (M) values for all the

polymers were calculated by measuring the [η] values followingthe Mark−Houwink equation. For the IDA polymers, thehomopolymer has greater molecular weight value than thecopolymers and comparison among the copolymers indicatethat with increasing 1-decene concentration M value decreases,whereas the trend is reversed for the IOA polymers; that is, thehomopolymer of IOA has lower molecular weight value thanthe copolymers and with increasing concentration of 1-decenecontent in the copolymer, molecular weight increases. Also, theIOA polymers have greater molecular weight values than theIDA polymers.The percentual difference (ΔM %) of molecular weight (M)

values taking that determined by Huggins equation as areference shows smallest ΔM % differences for the Kraemerequation.

Performance Evaluation of the Prepared Additives asPPD. PP of polymer solutions of different mass fractionsranging from 0.010 to 0.030 was tested and the results aretabulated in Table 5 (in base oil BO1) and Table 6 (in base oilBO2), which indicates that the prepared compounds have a lowPP and they can be effectively used as a PPD. In most of thecases, the efficiency increases with decreasing concentration ofadditive-doped solution and the trend is opposite in some cases(P-5 and P-6 in Table 6). The reason for the former is thesolvation power of the oil. With decreasing temperature, anysolvent gradually becomes less efficient in solvation and whenthe molecular weight of the solute and its concentrationincreases, solvation becomes even lesser. Again, hydrodynamicvolume of the polymer doped in oil may be considered toexplain the increasing PPD properties with the increase inadditive concentration. With increase in the concentration of

Figure 2. Plot of PWL vs T for the polymers of isooctyl acrylate,where PWL is the percent weight loss of the polymer and T istemperature in Kelvin: ◇, P-5; ▼, P-6; +, P-7; ●, P-8.

Figure 3. Plot of log ηsp versus log C[η], where ηsp is the specificviscosity of the polymer solution in toluene, C is the mass fraction ofthe polymer in toluene solution, and [η] is the intrinsic viscosity of thepolymer solution in toluene obtained by using the Huggins equation:○, P-1; □, P-2; Δ, P-3; ■, P-4; ◇, P-5; ▼, P-6; +, P-7; ●, P-8.

Table 5. Pour Point (PP) of the Additives Doped in Base Oil (BO1)a

PP/°C in the presence of

x2b P-1 P-2 P-3 P-4 P-5 P-6 P-7 P-8

0.000 −3.0 −3.0 −3.0 −3.0 −3.0 −3.0 −3.0 −3.00.010 −6.2 −9.9 −11.0 −11.6 −15.2 −12.4 −12.9 −13.60.020 −6.0 −9.7 −10.6 −11.2 −15.0 −11.6 −12.2 −13.40.030 −6.1 −9.5 −10.2 −11.0 −14.6 −9.4 −11.1 −11.9

aThe uncertainty in determining the PP temperature is within the range ± 0.1°. bMass fraction of the additive.

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the polymer doped in oil, the polymer−oil interaction as well asthe hydrodynamic volume of the polymer increases. Also, bothhomopolymer and copolymers of IOA act as better PPD thanthe polymers of IDA.Performance Evaluation of the Prepared Additives as

VII. The dynamic viscosity and VI values, of the preparedpolymers in base oil (BO1) are tabulated in Table 7 and Table8, respectively. The same data of all the polymers in BO2 are

recorded in Table 9 and Table 10, respectively. In general,dynamic viscosity of the prepared solutions increases with theincreasing concentration of the additives irrespective of thenature of the base oils. A similar trend is also observed in thecase of calculated VI values of the respective additive-dopedbase oils.Effect of Monomers on VI. The data shows that the VI for

any IDA + 1-decene copolymer is lower than that for the

respective IOA + 1-decene copolymer. Also, HIDA is of lowerVI than HIOA; that is, longer chain length and short branchingof the alcohol contribute less toward VI values than do shortchain and longer branching. This result was ascribed to thelower molecular weight of the IDA polymers compared to theIOA polymers because polymerizability of IOA is greater thanthe polymerizability of IDA.

Effect of 1-Decene Concentration in the Feed on VI.The data of VI values indicate that, for IDA + 1-decenecopolymers, the values decrease with increasing content of 1-decene for the same concentration of the polymer solution inboth the base oils. But, for IOA + 1-decene copolymers, thetrend is reversed. This may be because of the reason relating tomolecular weight.

Effect of Additive Concentration on VI. The data ofTable 8 and Table 10 indicates that with increasingconcentration of the prepared polymers in solution, VIincreases. The reason for this may be, while the viscosity ofthe lube oil gets decreased at higher temperature, the polymermolecules may effectively thicken the oil by changing its shapefrom tight coil to expanded ones due to increased polymer−solvent interaction. Increase in viscosity due to the thickeningeffect of the polymer molecule cancels out viscosity reductiondue to a higher temperature. Again, a higher polymerconcentration will show a higher viscosity index compared toa lower one as an increase of polymer concentration increasestotal volume of polymer micelles in the solution.1,12

A number of additives are available now-a-days but most ofthem are used either as PPDs2,16−18 or as VIIs.1,19,20 Thepresent investigation showed multifunctional additive perform-ance (PPD as well as VII), and thus these additives are

Table 6. Pour Point (PP) of the Additives Doped in Base Oil (BO2)a

PP/°C in the presence of

x2b P-1 P-2 P-3 P-4 P-5 P-6 P-7 P-8

0.000 −6.0 −6.0 −6.0 −6.0 −6.0 −6.0 −6.0 −6.00.010 −9.6 −11.3 −11.8 −12.0 −16.4 −18.5 −17.9 −15.40.020 −9.0 −10.9 −11.4 −11.8 −17.0 −19.4 −17.2 −14.80.030 −8.7 −10.1 −11.2 −11.4 −17.7 −20.0 −16.1 −14.0

aThe uncertainty in determining the PP temperature is within the range ± 0.1°. bMass fraction of the additive.

Table 7. Dynamic Viscosity Values of the Additives Doped in Base Oil (BO1)a.

dynamic viscosity (·103/Pa·s) in the presence of

x2b T/K P-1 P-2 P-3 P-4 P-5 P-6 P-7 P-8

0.000 313 5.97 5.97 5.97 5.97 5.97 5.97 5.97 5.97373 1.48 1.48 1.48 1.48 1.48 1.48 1.48 1.48

0.010 313 6.15 6.13 6.07 6.06 6.11 6.04 6.02 6.11373 1.52 1.52 1.51 1.50 1.51 1.49 1.49 1.53

0.020 313 6.21 6.20 6.13 6.18 6.25 6.10 6.08 6.18373 1.54 1.53 1.52 1.53 1.57 1.51 1.51 1.55

0.030 313 6.29 6.28 6.22 6.25 6.36 6.17 6.17 6.27373 1.55 1.54 1.54 1.54 1.63 1.52 1.54 1.58

0.040 313 6.39 6.37 6.29 6.35 6.46 6.24 6.26 6.32373 1.58 1.58 1.56 1.57 1.68 1.54 1.57 1.60

0.050 313 6.44 6.46 6.38 6.42 6.57 6.31 6.32 6.39373 1.60 1.60 1.58 1.58 1.72 1.56 1.59 1.63

0.060 313 6.52 6.56 6.44 6.51 6.65 6.39 6.40 6.50373 1.62 1.62 1.60 1.60 1.77 1.59 1.62 1.66

aT is the temperature in Kelvin. The uncertainty in determining dynamic viscosity is within the range ± 0.33 %. bMass fraction of the additive.

Table 8. VI Values of the Additives Doped in Base Oil(BO1)a

VI in the presence of

x2b P-1 P-2 P-3 P-4 P-5 P-6 P-7 P-8

0.000 85 85 85 85 85 85 85 850.010 92 91 90 88 91 86 89 980.020 94 93 92 91 103 87 93 1020.030 95 94 93 93 119 89 97 1080.040 100 99 97 96 125 91 103 1110.050 102 100 99 97 130 97 107 1140.060 105 103 101 100 136 103 112 120

aT is the temperature in Kelvin. The uncertainty in determining VI iswithin the range ± 0.53 %. bMass fraction of the additive.

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considered as being more useful in field applications comparedto the existing additives.

■ CONCLUSIONThe homopolymer and copolymers of isooctyl acrylate arebetter in thermal stability, have greater intrinsic viscosity andmolecular weight in toluene solvent, and also of have better VIIor viscosity modifier and PPD properties compared to thehomopolymer and copolymers of isodecyl acrylate. Thus it canbe concluded that, polymers of isooctyl acrylate perform asbetter multifunctional lube oil additives than those of isodecylacrylate.

■ ASSOCIATED CONTENT*S Supporting InformationExperimental calculations and additional data; times of flow; IRand NMR spectra. This material is available free of charge viathe Internet at http://pubs.acs.org.

■ AUTHOR INFORMATIONCorresponding Author*E-mail: pizy12@yahoo.com. Tel.: 9474441468.FundingThe authors are thankful to UGC, New Delhi, for financialsupport.NotesThe authors declare no competing financial interest.

■ REFERENCES(1) Nassar, A. M. The Behavior of Polymers as Viscosity IndexImprovers. Petrol. Sci. Technol. 2008, 26, 514−522.(2) Khidr, T. T. Synthesis and Evaluation of Copolymers as PourPoint Depressants. Petrol. Sci. Technol. 2007, 25, 671−681.(3) Ahmed, N. S.; Nassar, A. M.; Nasser, R. M.; Khattab, A. F.;Abdel-Azim, A. A. A. Synthesis and Evaluation of Some PolymericCompounds as Pour Point Depressants and Viscosity Index Improversfor Lube Oil. Petrol. Sci. Technol. 2008, 26, 1390−1402.(4) El-Gamal, I. M.; El-Batanoney, M. H.; Ghuiba, F. M. Synthesisand Evaluation of Some Acrylate Polymers as Pour Point Depressantsfor Waxy Crude Oils. Proc. Al-Azhar Eng. Int. Conf. 1993,No. December 18−21, 93.(5) Andre, L. C. M.; Elizabete, F. L. Influence of Ethylene Co-vinylAcetate Copolymers on the Flow Properties of Wax Synthetic Systems.J. Appl. Polym. Sci. 2002, 85, 1337−1348.(6) Anwar, M.; Khan, H.; Nautiyal, S.; Agrawal, K.; Rawat, B.Solubilised Waxes and Their Influence on the Flow Properties of LubeOil Base Stocks. Petrol. Sci. Technol. 1999, 17, 491−501.(7) Delpech, M. C.; Coutinho, F. M. B.; Habibe, M. E. S. ViscometryStudy of Ethylene−Cyclic Olefin Copolymers. Polym. Test. 2002, 21,411−415.(8) Mohamed, M. M.; Naga, H. H. A. E. L.; Meneir, M. F. E. L.Multifunctional Viscosity Index Improvers. J. Chem. Technol.Biotechnol. 1994, 60, 283−289.(9) Mello, I. L.; Delpech, M. C.; Coutinho, F. M. B. Albino, F. F. M.Viscometric Study of High-Cispolybutadiene in Toluene Solution. J.Braz. Chem. Soc. 2006, 17 (1), 194−199.(10) Ghosh, P.; Das, T.; Nandi, D. Synthesis of Copolymers andHomopolymers of Methyl Methacrylate and Styrene and Studies ontheir Viscometric Properties in Three Different Solvents. Res. J. Chem.Environ. 2009, 13 (1), 17−25.(11) Oliveira, C. M. F.; Andrade, C. T.; Delpech, M. C. Properties ofPoly(methylmethacrylate-g-propylene oxide) in Solution. Polym. Bull.1991, 26, 657−664.(12) Ghosh, P.; Das, M.; Upadhyay, M.; Das, T.; Mandal, A.Synthesis and Evaluation of Acrylate Polymers in Lubricating Oil. J.Chem. Eng. Data 2011, 56, 3752−3758.(13) Ghosh, P.; Das, T.; Nandi, D. Synthesis Characterization andViscosity Studies of Homopolymer of Methyl Methacrylate andCopolymer of Methyl Methacrylate and Styrene. J. Solution Chem.2011, 40, 67−78.(14) Tanveer, S.; Prasad, R. Enhancement of Viscosity Index ofMineral Base Oils. Ind. J. Chem. Technol. 2006, 13, 398−403.(15) Delpech, M. C.; Oliveira, C. M. F. Viscometric Study ofPoly(methyl methacrylate-g-propylene oxide) and Respective Homo-polymers. Polym. Test. 2005, 24, 381−386.

Table 9. Dynamic Viscosity Values of the Additives Doped in Base Oil (BO2)a

dynamic viscosity (·103/Pa·s) in the presence of

x2b T/K P-1 P-2 P-3 P-4 P-5 P-6 P-7 P-8

0.000 313 20.31 20.31 20.31 20.31 20.31 20.31 20.31 20.31373 3.25 3.25 3.25 3.25 3.25 3.25 3.25 3.25

0.010 313 21.34 21.42 21.38 21.30 21.78 21.65 21.84 21.84373 3.42 3.42 3.41 3.40 3.50 3.45 3.54 3.60

0.020 313 21.45 21.49 21.50 21.40 21.95 21.79 21.98 21.97373 3.45 3.45 3.44 3.42 3.55 3.49 3.61 3.64

0.030 313 21.54 21.56 21.60 21.48 21.89 21.92 22.08 22.09373 3.47 3.47 3.46 3.44 3.59 3.53 3.64 3.68

0.040 313 21.66 21.70 21.73 21.61 22.01 22.02 22.19 22.19373 3.51 3.50 3.51 3.49 3.63 3.58 3.68 3.71

0.050 313 21.80 21.79 21.84 21.74 22.31 22.12 22.30 22.34373 3.58 3.56 3.56 3.54 3.84 3.61 3.73 3.77

0.060 313 21.92 21.90 21.94 21.86 22.55 22.23 22.40 22.49373 3.63 3.61 3.60 3.57 4.11 3.66 3.78 3.86

aT is the temperature in Kelvin. The uncertainty in determining kinematic viscosity is within the range ± 0.14 %. bMass fraction of the additive.

Table 10. VI Values of the Additive Doped in Base Oil(BO2)a

VI in the presence of

x2b P-1 P-2 P-3 P-4 P-5 P-6 P-7 P-8

0.000 80 80 80 80 80 80 80 800.010 87 87 86 86 90 87 93 980.020 89 89 88 87 94 89 98 1000.030 90 89 88 88 97 92 100 1020.040 93 92 92 91 100 95 101 1030.050 97 96 95 94 112 97 104 1060.060 100 99 98 96 124 100 106 111

aT is the temperature in Kelvin. The uncertainty in determining VI iswithin the range ± 0.53 %. bMass fraction of the additive.

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(16) Jung, K. M.; Chun, B. H.; Park, S. H.; Lee, C. H.; Kim, S. H.Synthesis of Methacrylate Copolymers and Their Effects as Pour PointDepressants for Lubricant Oil. J. Appl. Polym. Sci. 2011, 120, 2579−2586.(17) Ghosh, P.; Das, T.; Nandi, D.; Karmakar, G.; Mandal, A.Synthesis and Characterization of Biodegradable PolymerUsed as aPour Point Depressant for Lubricating Oil. Int. J. Polym. Mater. 2010,59, 1008−1017.(18) Du, T.; Wang, S.; Liu, H.; Song, C.; Nie, Y. The Synthesis andCharacterization of Methacrylic Acid Ester-Maleic Anhydride Copoly-mer as a Lube Oil Pour Point Depressant. Petrol. Sci. Technol. 2012, 30,212−221.(19) Ghosh, P.; Das, T.; Karmakar, G.; Das, M. Evaluation ofAcrylate-Sunflower Oil Copolymer as Viscosity Index Improvers forLube Oils. J. Chem. Pharm. Res. 2011, 3 (3), 547−556.(20) Ghosh, P.; Das, T.; Das, M. Evaluation of Poly(acrylates) andTheir Copolymer as Viscosity Modifiers. Res. J. Chem. Sci. 2011, 1 (3),18−25.

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