Synthesis And Characterization Of Copolymers As Pour Point Depressants And Viscosity Index Improvers For Lubricating Oil

(1-hexene-co-ditetradecyl maleate)


Introduction
Lubrication oil was used to reduce friction resulting from the movement of one surface over another, or from the surfaces of overlapping moving parts, which reduces energy loss due to friction.It also reduces the wear of moving parts, and reduces the heat generated during operation.The materials used for this purpose are called lubricating oils.Lubricants are usually gases, liquids, Semi-liquids, solids, or a mixture of liquid, solid and gases.Lubricants contain at least one additive, and sometimes oils contain several different additives to lubricating oils varies, often up to 30% or more [1].Oils often consist of linear or branched alkanes or isoparaffins, cycloparaffins, aromatic rings, and very small amounts of heterocyclic Compounds [2].Mineral oils have a major problem during low temperatures due to the presence of waxy hydrocarbons whose solubility decreases with decreasing temperature.It crystallizes and separates from the oil, forming a solid three-dimensional crystal network that traps the oil inside and prevents it from flowing or spillings, it expressed as the pour point (PP), which is the lowest temperature at which the oil spills [3].Viscosity is one of the important Factors that must be taken into account when choosing lubricating oils.When the Viscosity of the oil is very low at the operating temperature, the oil film is not sufficient and therefore corrosion or burning Occurs.If the viscosity is too high, the resistance becomes large loss in Energy and temperature rise between movingparts [4].Various types of additives are used to lubricating oils to improve some of the existing properties or add new properties to the oil.These additives include corrosion inhibitors, anti-wear, anti-oxidants , anti-friction, pour point depressants (PPP), and viscosity index improver (VI) [5].Pour point depressants (PPD S ) and viscosity index improvers (VIs), sometimes called viscosity modifiers, are among the most important additives to add to lubricants.When the Temperature drops, the polymeric chains shrink and do not affect the viscosity of the oil, while at high temperatures the Polymeric chains relax and expand in the oil, so an increase in viscosity occurs [6].pour point depressants (PPDs), they are substances added to lubricating oils whose purpose is to effectively improve the fluidity of the oil at low temperatures because the hydrocarbon compounds in the oil crystallize and separate as a result of their low solubility at low temperatures [7].

Instruments
Infrared spectra of as prepared copolymers were recorded using KBr and SHIMADZU FTIR 8400 spectrometer.the structures of the prepared copolymers were also monitored by 1 HNMR spectra using Bruker Avance 500 MHZ spectrometer, a solvent (DM SO-d 6 ) and a reference Material (TMS).molecular weights of the prepared polymers are determined by Gel permeation Chromatography (GPC), by use of tetrahydrofuran as a solvent.thermal analysis were recorded using a TGA Q500 V6.7 device in the presence of argon, with a flow rate of 50 ml/min , heating rate of 10/ min C 0 , and a temperature of (20-900)C 0 .

Polymerization and esterification reactions
(1-hexen-co-maleic anhydride) and (methyl methacrylate-co-maleic anhydride) copolymers were prepared by free radical polymerization according to The prepared copolymers was isolated from the reaction mixture by precipitation with diethyl ether, washed with benzene and dried at 50C 0 .the prepared Poly ( 1-hexene -comaleic anhydride) was esterified with two type of alcohol (1-tetradecand) and (1hexadecanol) with ratio of 1:1 and P-TSA 1% (w/w) as initiator at 100C 0 , for three hours, while the poly(methyl methacrylate-co-maleic anhydride) was reacted with (1-tetrade canol) in the same condition the reaction was contained until the theoretical amount of water was collected.Scheme1 Show the reaction mechanism to prepared the Copolymers and it esterification.

Evaluation of prepared Polymers as pour point depressants (PPDs) and viscosity index improvers (Vlls)
Copolymers were evaluated as viscosity index improvers in three types of base oils by determining the kinematic viscosity (KV) of oils containing Copolymers at 40C 0 and 100 C 0 , using different concentrations (1000-5000) ppm according to ASTM D 2270 method [8].while for pour point depressants according to ASTM D 97 method [9].

FTIR
Figure (1) show the FTIR spectra of the Poly(1-hexene -CO-maleic anhydride).from the figure, the two peaks at 1778 cm -1 and 1859 cm -1 correspond to the absorption of C=O bond of the maleic anhydride while the peak at 1064cm -1 assigned to the C-O bond in the maleic anhydride, two peaks appeared at 2935 cm -1 and 2870 cm -1 assigned for the methyl and methylene groups respectively.Figure (2) shows the esterification of maleic anhydride groups with 1-tetradecanol the peak at 1724 cm -1 representing the ester group, with the disappearance of the C=O peak which characterized for maleic anhydride.the appearance of ester peak at 1165 cm -1 .Figure (3) shows the FTIR spectra esterification of maleic anhydride with 1-hexadecanol, the Peak appearance 1728 cm -1 was attributed for the ester group and the peak at 1165 cm -1 for C-O ester bond with the disappearance of the C=O peak maleic anhydride.Figure ( 4) represent the FTIR spectra of poly(methyl methacrylate-CO-maleic anhydride) from the figure two peak appear at 1782 cm -1 and 1855 cm -1 for the C=O group of maleic anhydride, with peak at 1065 cm -1 representing the C-O bond. the two peaks at 1728cm -1 and 1149 cm -1 was attributed to the C=O and C-O of the acrylate, while the peak at 2955 cm -1 was asserted for the methyl group.the esterification of poly(methyl methacrylate -CO-maleic anhydride) by 1-tetradecanol was Shows. Figure (5) appears two peaks at 2924 cm -1 and 2854 cm -1 which assigned to the methyl and methylene groups respectively.also a peak at 1165 cm -1 assigned to C-O bond of the ester [10].with the peaks disappearance of the maleic anhydride while the signal appears.at 2.9 ppm represent the Proton (c) near the carbonyl group .the signal appear at 3.6ppm was signed for the Protons of methyl group (d) [11].Figure (10) shown the 1 HNMR spectra for the esterification of poly(methyl methacrylate-co-maleic anhydride).the same signals appears for the poly(methyl methacrylate-co-maleic anhydride), only two new signals appears at 3.8 ppm and 4.2 ppm for protons (g) and (f) respectively resulting from ring opening of the maleic anhydride.The appearance of weak signal in the region 7.3 ppm to 7.7 ppm represents the protons of the decomposition of the initiator (benzoyl peroxide) [12].  .

Table (3) the mean molecular weight of prepared polymer
Performance of the prepared polymers as pour point different concentrations (1000-5000) ppm of the prepared polymers were added to the three types of base oils.the experimental results was shown in table (3) that the pour point was decreased for all three types of base oil until the (5000) ppm of the concentration of the prepared copolymer and decreased with increasing the concentration of the polymer to 4000 ppm.this was attributed to the solubility of the base oil the prepared polymer because the solubility ability of the materials decreased with decreasing the temperature [13].polymer (A) with molecular weight (12030 g /mol) was more effective than polymer (C) with molecular weight (16068 g/mol), and polymer (B) with molecular weight (44194 g/mol) was the less effective in decreasing the pour Point.

Performance of the prepared polymers as viscosity index improvers
Tables (4,5,6) shows that all the prepared copolymers are effective as viscosity index improvers, but copolymer (B) is more effective than copolymers (A,C), and this can be explained by the increase in the molecular weight of the copolymers, (molecular weight 44194 g/mol).Most of the viscosity index improvers are Long-chain copolymers with high molecular weight, whose effect is weak at low temperatures because they are in the form of coiled micelles, and at higher temperatures the strength of the solvent increases, which facilitates the expansion of coiled micelles and compensates for the low viscosity of the oil [14].the viscosity index of the three base oils increases with increasing the concentration of the Polymers because the long chains of the copolymer in the form of coils in the oil and when the temperature rise, these chains become more relaxed and tend to expand completely.So the interaction between the polymer chains and the oil increases, so increases in the volume and as result increase the viscosity of the base oil at higher temperature [15].as shown in figure 17.

Conclusions
From the results obtained in this research, the following conclusions can be written: 1.All prepared compounds dissolve in base oils.2.All prepared compounds are effective as pour point depressants and viscosity index improvers.
3. With an increase in the concentration of additives, increase viscosity index (VI).4. As the concentration of additives increases, the effectiveness of polymers as pour point depressants decreases.5.The efficiency of the prepared compounds as pour point depressants increases with the increase in the alkyl chain length of the alcohol used.

Fig. 14 Fig. 16
Fig.14 Variation of pour point of the three base oils where adding different Concentrations of polymer A Fig.17 Expansion and contraction of the polymeric coils [ 16 ] .

Fig. 20
Fig. 20 Variation of Viscosity index (VI) of the three oils when adding different concentration of polymer (C)