lance of the finished lubricant. Esters have been used in synthetic lubricants for more than 60 years and continue to grow as the drive for efficiency make operating environments more severe. Because of the complexity involved in designing, selecting, and blending of an ester base stock, the choice of the optimum ester should be left to qualified ester engineer who can better balance the desired properties [1]. Today there is a growing concern about the future availability of petroleum based products. In addition, millions of tons of lubricants are dumped into the environment through leakage, exhaust gas and careless disposal. Some of the wastes are resistant to biodegradation and are threats to the global nature. Thus, there are two major issues confronting the lubricant industries today: the search for raw materials that are renewable and products that are biodegradable or eco-friendly for the environment [2]. Aus Wissenschaft und Forschung 12 Tribologie + Schmierungstechnik · 65. Jahrgang · 5/ 2018 1 Introduction and background Esters are a broad and diverse family of synthetic lubricant base stocks which can be custom designed to meet specific physical and performance properties. The Inherent polarity of esters improves their performance in lubrication by reducing volatility, increasing lubricity, providing cleaner operation, and making the products biodegradable. A wide range of available raw materials allow an ester designer to optimize a product over a wide range of variables in order to maximize the performance and value to the client. They may be used alone in very high temperature applications for optimum performance or blended with PAOs or other synthetic base stocks where their complementary properties improve the ba- Synthetic Complex Malonic Esters as Eco-Friendly Lubricants L. E. Mirci, L. Bogatu* Vorliegende Arbeit stellt die Ergebnisse betreffend die Synthese und Charakterisierung als bioabbaubare Schmiermittel von einigen komplexen Estern dar, ausgehend von der Malonsäure, verschiedenen Glycolen, wie Triäthylen, Diäthylen, Monoäthylen, 1,3- Propylen, 1,4-Butylen, 1,5-Pentamethylenglykol und Hexamethylenglykol, wobei die Isotridecanol iso- C 13 H 27 als Endglied oder als ein „Capping Element“ verwendet wird. Auf Grund einer regelmäßigen Alternation oder des Prinzips der sukzessiven Verteilung der polaren und nichtpolaren chemischen Funktionen, gleichmäßig verteilt auf die Länge eines genügend langen Moleküls, entstehen wertvolle synthetische bioabbaubare Schmiermittel. Diese Produkte weisen bedeutende tribologische Eigenschaften auf, wie z.B. einen hohen Viskositätskoeffizienten, hohen Flammpunkt, exzellent Pour Point und sehr gute Schmiereigenschaften. Schlüsselwörter Synthetische Schmieröle; Malonsäure; Glycole, isotridecanol, iso-C 13 H 27 The paper presents results concerning the synthesis and characterisation as base oils lubricants considered as eco-friendly products, derivatives, of some complex esters realized on the basis of malonic acid, different glycols, such as triethylene, diethylene,(mono) ethylene, 1,3 propylene, 1,4 butylene, 1,5 pentamethylene and 1,6 hexamethylene glycol, respectively, along with isotridecanol, iso-C 13 H 27 , used/ considered as an end/ final segment or a capping element. On the basis of a theoretical concept of regular alternation or successive distribution principle of the polar and non-polar chemical functions equally issued/ shared out on the length of a sufficient long molecule, valuable synthetic ester lubricants/ base oils with biodegradability potential, were performed. These products showed remarkable good tribological properties, such as adequate viscosity indices, high flash points, excellent pour points values and very good lubricity features. Keywords Synthetic ester base oils; malonic acid; glycols; isotridecanol, iso-C 13 H 27 Kurzfassung Abstract * Prof. Liviu E. Mirci University Politehnica Timisoara Faculty of Chemical Engineering,Timisoara, Romania Prof. Liana Bogatu Faculty of Petrochemistry and Petroleum Technology Universitatea de Petrol si Gaze, Ploiesti, Romania T+S_5_18.qxp_T+S_2018 28.08.18 13: 50 Seite 12 By taking in considerations these aspects the literature of the last decade can offer several representative examples. One must mention the paper of Firdovsi et al., which reports the synthesis of some esters based on oxypropylated trimethylol propanes considered as synthetic lubricants. Thus, this research stated the aim to study the effects of introducing oxypropyl segments into the trimethylol propane (TMP) esters along with lowering the linear chain length from C5-C9 to C5-C6 on the properties of base lubricants. Various amounts of oxypropylene segments were introduced into the TMP and obtained polyols subsequently esterified by pure C5-, C6-, a mixture of C5-C6aliphatic monocarboxylic acids of normal structure (SFAc mixture ). Introducing oxypropylene segments into TMP skeleton along with lowering the carboxylic acid chain length from C5-C9 to C5-C6, ester base lubricants obtained improved mechanical and wear preventive characteristics. These obtained materials have high boiling points under reduced pressure, while the synthesized compounds showed improved properties such as high viscosity at 100 °C, low pour point, high flash point, and totally excellent viscosity-temperature properties than simple TMP esters and some literature reported ester base lubricants [3]. Within the same way a paper signed by Robiah Yunus and co-workers, reports the synthesis of Palm Oil Trimethylolpropane (TMP) esters with improved pour points [4].Thus, in order to improve the low temperature properties of palm oil based TMP esters, which are well below the requirements set by the lubricants’ manufacturers, the high oleic content palm oil based TMP ester with a pour point between -10 and -32 °C was synthesized. The synthesis of palm oil polyol esters was performed by transesterification of fractionated palm oil methyl esters with TMP using sodium methoxide as a catalyst. Nearly complete conversion to palm. TMP triesters (98 % w/ w) was obtained. The palm oil methyl esters were fractionated at 150-180 °C, and 0,1 mbar prior to the synthesis to reduce the saturated fatty acid content. The fractionation and reaction took place using the same experimental setup. The effects of composition on pour points, viscosity and viscosity index of the high oleic content palm oil based TMP esters, were also evaluated. The concentration of C 16.0 methyl ester in the starting material should be below 10 % w/ w to ensure that the pour points of high oleic content palm oil based RMP esters are below -30 °C. In addition, the reaction conversion to triester must also be maintained above 90 % w/ w to produce TMP esters with excellent pour points. Operating temperature had a negligible effect on the reaction yield so long the temperature was kept above 120 °C. There were small variations in the viscosities and viscosity index values of high oleic content palm oil based TMP, in the region of 50 cSt and 199, respectively [4]. The patent literature also offers a lot of attempts in order to produce new ester lubricants with improved characteristics. Under this frame one must mention a patent which deals with the realization of a crankcase lubricating oil formulation with high oxidative stability, prepared from a base stock which comprises at least one synthetic ester selected from the group consisting of: polyol esters, synthetic esters having between 5-35 % unconverted hydroxyl groups, based on the total amount of hydroxyl groups in the polyol, and synthetic esters combined with at least one additional functional group which is capable of increasing the polarity of the functionalized synthetic ester, wherein the base stock has an oxygen , nitrogen or halogen content of at least 15 % wt.%, based on total weight of the base stock; and a lubricant package [5]. Another patent claims the discovery of a high temperature lubricant composition having improved antiwear properties and resistance to degradation. The lubricant composition comprises a synthetic ester base stock and as antiwear additive a hydrocarbon insoluble, synthetic ester soluble, aryl diphosphate ester composition containing no more than 2 wt.% triaryl phosphate. Surprisingly, although the aryl diphosphate ester composition in comparison with triaryl phosphate esters is stable at high temperature lubricating conditions, it gives poor antiwear results when used per se as a high temperature lubricant . In contrast, the aryl diphosphate ester composition when used in minor amounts in a synthetic ester basestock lubricant, provides excellent antiwear at high temperature [6]. An interesting patent reports the use as lubricants for internal combustion engines, based on synthetic esters or mixtures thereof, preferably in combination with synthetic hydrocarbon fluids. It is emphasized that such compositions, when used to lubricate an internal combustion engine, reduces the fuel consumed by such engine. Thus, the invention provides an organic fluid composition comprising a lubricating oil having from about 20 % by weight to about 40 % by weight of a hydroxylcontaining synthetic ester oil of lubricating viscosity, or mixtures thereof, and from about 60 % by weight to about 80 % by weight of a synthetic hydrocarbon lubricating oil consisting essentially of a hydrogenated oligomer of an alpha olefin having from 6 to 12 carbon atoms [7]. One must necessarily mention the remarkable team of Carolyn Duncan with a long and valuable contribution in the field of ester lubricants, with a representative Patent in which they report the realization of a biodegradable synthetic ester base stock [8]. This material comprises a blend of the following base stocks: (A) The reaction product of: (1) a branched or linear alcohol having the general formula R(OH) n , wherein R is an aliphatic or cyclo-aliphatic group having from about 2 to 20 carbon Aus Wissenschaft und Forschung 13 Tribologie + Schmierungstechnik · 65. Jahrgang · 5/ 2018 T+S_5_18.qxp_T+S_2018 28.08.18 13: 50 Seite 13 compounds. The results obtained showed that ethylhexyl 9-(octanoyloxy)-10-(behenoxy) octadecanoate with behenyl mid-chain ester exhibited the most favorable low temperature performance (PP -48 °C), while ethylhexyl 9-(octanoyloxy)-10-(octyl oxy)octadecanoate octyl midchain ester exhibited higher oxidation stability (OT 142 C) than the other synthetic ester oils [10]. Within the same global drive towards biodegradable products, the literature recorded a study which reports results concerning the lubrication properties of trimethylolpropane esters based on palm oil and palm kernel oils [11]. Thus, trimethylolpropane [2-ethyl-2-(hydroxymethyl)-1,3-propanediol] (TMP) esters based on palm and palm kernel oils were synthesized, their lubrication properties evaluated, and their potential as base stock for biodegradable lubricants assessed. Two types of TMP esters have been taken in consideration: palm kernel (PKOTE) and palm oil (PPOTE) TMP esters, derived from palm oil and palm kernel methyl esters, respectively. Under these circumstances, high Viscosity Indices (VI) ranges between 170 to 200 were recorded for these base stocks. Pour points (PP) were relatively high, between 4 to -1 °C, but were improved to at least -33 °C in high oleic palm oil TMP esters. The presence of methyl esters was found to improve wear, but hydroxyl groups in mono and diesters had negative effects at high concentrations. The effects of chemical structure and impurities on wear properties and oxidative stability were also studied. Differences in chemical structure of PKOTE and PPOTE were shown to affect friction and wear results. Both base fluids exhibit oxidative stability comparable to other high oleic base fluids [11]. Within the same direction of preoccupations, an American study was reported dealing with chemically modified vegetable oils [12]. As it is unanimously accepted, vegetable oils are recognized as rapidly biodegradable and are thus promising candidates as base fluids in environment friendly lubricants. Lubricants based on vegetable oils display excellent tribological properties, high viscosity indices, and flash points. However, in order to compete with mineral-oil-based lubricants, some of their inherent disadvantages, such as poor oxidation and lowtemperature stability must be corrected. One way to address these problems is chemical modification of vegetable oils at the sites of unsaturation. The chemically modified soybean oil derivatives having diester substitution at the sites of unsaturation have a real potential to be used in the formulation of industrial lubricants. Such products exhibit superior low temperature flow properties, improved thermo-oxidative stability, and better friction and wear properties [12]. A similar study realized by Chinese researchers is reported dealing with epoxidized rapeseed oil [13]. The application of epoxidized rapeseed oil as a biodegradable lubricant is described. The epoxidation treatment has no adverse effect on the biodegradability of the base stock. Aus Wissenschaft und Forschung 14 Tribologie + Schmierungstechnik · 65. Jahrgang · 5/ 2018 atoms and n is at least 2; and (2) mixed acids comprising about 30 to 80 molar % of a linear acid having a carbon number in the range between about C 5 to C 12 , and about 20 to 70 molar % of at least one branched acid having a carbon number in the range between about C 5 to C 10 and wherein no more than 10 % of the branched acids used to form the biodegradable synthetic ester base stock contains a quaternary carbon; wherein the ester base stocks exhibits the following properties: at least 60 % biodegradation in 28 days as measured by the Modified Sturm test, a pour point of less than -25 °C; and a viscosity of less than 7500 cps at - 25 °C; and (B) another base stock having at least 60 % biodegradation in 28 days measured by the Modified Sturm test; whereby the blended product has a biodegradation in 28 days as measured by the Modified Sturm test which is greater than either (A) or (B) alone [8]. An improved synthetic ester lubricant base stock formed by reacting at least one of trimethylolpropane and monopentaerythritol with a mixture of aliphatic monocarboxylic acids is provided [9]. The mixture of acids including straight-chain acids having from 5 to 10 carbon atoms and an iso-acid having from 6 to 10 carbon atoms, preferably iso-nonanoic acid. The base stock is mixed with a conventional ester lubricant additive package to form a lubricant having a viscosity at 210 °F, of at least 5.0 centistokes and pour point of at least as low as -65 °F. The resulting lubricants have a decreased tendency to form deposits in gas turbine engines [9]. One must emphasize again that for environmental reasons, as well as the dwindling source of petroleum, a new class of environmentally acceptable and renewable biolubricants based on plant oils is available. Even though plant oils possess excellent lubricant-related properties, there are some concerns about using it as biolubricant base oil. In an extended academic study some series of structures derived from oleic acid which can be used as synthetic biolubricant base stocks are presented [10]. In order to realize this objective, a process was stated which consists in a systematic approach to modify chemically oleic acid oil to yield a base stock capable of operating at low temperature. Preparation was based on epoxidation of acyl double bond, opening of the formed oxirane ring in an appropriate medium and acetylation of free hydroxyl group. Based on the results obtained, increasing the chain length of the mid-chain ester had a positive influence on the low temperature properties of diesters because they create a steric barrier around the individual molecules and inhibits crystallization, resulting in lower pour point (PP). But the trends for PP run counter to that of oxidation onset temperature (OT), i.e. increasing chain length is a benefit to PP, but a detriment to OT. Also it is evident that hydrogen bonding is a critical parameter influencing the low temperature properties and oxidation stability of synthetic esters. Increasing the hydrogen bond amount will lead to the increase pour point (PP) and decrease the oxidation stability of these T+S_5_18.qxp_T+S_2018 28.08.18 13: 50 Seite 14 Epoxidized rapeseed oil has superior oxidative stability compared to rapeseed oil based on the results of both oven tests and rotary oxygen bomb tests. Moreover, the oxidative stability can be dramatically promoted by the addition of a package of antioxidants. The epoxidized rapeseed oil has better friction-reducing and extreme pressure abilities according to tribological investigations. Formation of a tribopolymerization film is proposed as explanation of the tribological performance of epoxidized rapeseed oil [13]. By analyzing the most representative directions of research recorded, one can observe that there is a constant effort in order to realize biodegradable lubricants, strongly requested by the market. These offered examples also indicate that this goal is accomplished either via chemical alteration of a triglyceride molecule of a vegetable oil, or via the realization of various esters, with more or less biodegradability capability. One can also firmly remark that, almost exclusively, the long, unsaturated chain (oleic, being the most representative) is responsible for the valuable, unique characteristics of vegetable oils, when considered as biolubricants. Any chemical modification of their structure will, obviously diminish drastically (even up to extinction ) the intrinsic features of the admitted, discussed, vegetable oil. Under this situation we have considered a new route of research, that is we realized an absolutely new class of special complex (tetra)esters which contain the valuable part of a triglyceride, that is the long, unsaturated aliphatic chain, mainly of oleic type, as such, that is unaltered or without any chemical modification. The products realized in this manner were defined as ”direct series”, while the reciprocal series when the end, capping element, is a long iso alcohol (either isodecanol or isotridecanol),were denominated as “reversed series”. For better understanding our research plan the general formula of the direct series has the following structure: R - COO - A - OOC - B - COO - A - OOC - R (I) where: A = radical of (mono) ethylene, 1,3 propylene, 1,4 butylene, 1,5 pentamethylene, 1,6 hexamethylene, diethylene and triethylene glycol, respectively B = malonic acid radical R = oleic radical, [-(CH 2 ) 7 -CH=CH-(CH 2 ) 7 -CH 3 ]. By using an original principle, unreported in the literature,which means the regular alternation or the successive distribution of the chemical polar functions (in fact, ester bridges) with the non-polar ones (aliphatic segments, saturated and/ or unsaturated hydrocarbon chains) equally distributed on the length of a sufficient/ satisfactory long/ large molecule, valuable complex esters have been synthesized. In an essential, general schematic, in the main or principled representation, the situation could be described by the following graphic form: ---------O--------O--------O--------O-------where: --------represents the non polar (aliphatic chain) chemical function O represents the polar chemical function (bridge, esteric group) Under this way, by arranging in an uniformly alternating manner the polar chemical function groups with the nonpolar ones, or by assembling these chemical functions in order to be equally distributed on the length of a of a long molecule and by observing that the unsaturated long aliphatic chain obtained from natural vegetable oils (oleic rest) blocks both ends of this realized molecule, one can expect from these compounds at least valuable lubrifying properties. In a more suggestive representation, this new conceived principle could be visualized within the following graphic form shown in Figure 1, in which the position of a lubricant and its supposed mechanism of action are also imagined, that is represented. On the occasion of some Congresses, held in Germany every two years (par ) (International Colloquiums on Tribology, Stuttgart/ Ostfildern ) we have firstly present- Aus Wissenschaft und Forschung 15 Tribologie + Schmierungstechnik · 65. Jahrgang · 5/ 2018 Figure 1: The regular alternation or successive distribution principle, the “myriopod (myriapod) concept” T+S_5_18.qxp_T+S_2018 28.08.18 13: 50 Seite 15 2 Experimental The glycols used, that is (mono) ethylene, 1,3 propylene, 1,4 butylene, 1,5 pentamethylene, 1,6 hexamethylene, diethylene and triethylene glycol, respectively, were pure chemical samples supplied by Merck, as well as malonic acid, while isotridecanol was afforded by BASF. The synthesis of these special complex esters was performed in a solution esterification process, by using an aromatic solvent, which acted also as an azeotropic agent for the extraction of water (toluene, preferably ), within either in an autocatalytic system or by using a solid catalyst, via two steps, according to a specific method described elsewhere [ 20,21 ]. The adequate purified products were characterized by chemical and physical indices specific to this class, while the rheological characteristic tribological features were determined by using standardized techniques. Thus, dynamic viscosity was measured by means of a rotation viscometer (Rheotest Type RV, VEB Prufgerate-Werk Medingen/ Dresden, Germany ), at 20 °C, measuring device S1, shear rate within the interval 1.6- 1310/ s. The four ball test was accomplished on a SETA machine (SETA-Shell Four Ball Lubricants Tester, Stanhope Seta, England), according to ASTM 2783-03 . Kinematic viscosity was determined with an Ubbelohde viscometer (Schott-Geräte GmbH, Hofheim, Germany) according to ASTM D 445-06, while the viscosity index, VI, was calculated from the data, conformably to ASTM 2770. The pour point was measured according to ASTM D 97- 06, and the flash point according to ASTM D 92-05. Note that in order to facilitate the reading of tables and make easier the identification of products, a coding system was used involving an abbreviation principle by taking into account the glycol used which represents in fact the only variant factor of the chemical structures of these derivatives, and also by mentioning the abridged forms MAL for malonic acid and ISOTRI (defining the isotridecanol), and “tri” for triethylene glycol, “di” for diethylene glycol, “mono” for monoethylene glycol, while the other glycols are abbreviated according to their formula, respectively. Consequently, we have named these products as follows: MAL-TRI-ISOTRI, MAL-DI-ISOTRI, MAL-MONO- ISOTRI, MAL-1,3-PROP-ISOTRI, MAL-1,4-BUT- ISOTRI, MAL-1,5-PENTA-ISOTRI and MAL-1,6-HE- XA-ISOTRI, respectively . Aus Wissenschaft und Forschung 16 Tribologie + Schmierungstechnik · 65. Jahrgang · 5/ 2018 ed this elaborated representation, defined consequently as the “myriopod (myriapod) concept“ By using the principle mentioned above, we have realized some special complex synthetic ester lubricants of an elaborated tetraester type on the basis of malonic acid, isotridecanol, considered as an end segment or a capping element and different glycols, respectively with biodegradability potential. These products are defined by the general formula (II): R - OOC - B - COO - A - OOC - B - COO - R (II) where: A = radical of (mono) ethylene, 1,3 propylene, 1,4 butylene, 1,5 pentamethylene, 1,6 hexamethylene, diethylene and triethylene glycol respectively B = malonic acid radical. -CH 2 - R = isotridecil, radical, iso C 13 H 27 -, For sure we must underline that the use of isotridecil radical as an end or a capping element was not fortuitous, and this reason was firmly grounded on the opinion that this part is a replicate much more close to the structure of the oleic part (used by us in the realization of so called ”direct series”) in vegetable oils and this similar structure could confer some valuable lubricant properties. On the basis of this program, and by evaluating these new created lubricant models, it becomes possible to quantify the influence of different chemical functions that are present in each considered molecule on overall properties, and we also could investigate the variation of the representative tribology properties as a function of the general chemical structure, that is of the variation in length/ structure brought in by the chosen glycol. The synthesized products showed some excellent tribological properties, such as reasonable good viscosity indices, good, that is high flash points, excellent pour points and remarkable lubricity properties. The results of some of our previous attempts were firstly presented, for instance, in an International Congress in Singapore [14], when the acid “B” was adipic acid, while the specific structure of these complex malonic derivatives, as well as the synthesis procedure, were protected by a patent [ 15]. We must underline that the results of our researches were reported some years ago accordingly, that is in the case of considered series of adipic and sebacic acids, respectively [16-21], while for this series some of the first results were presented in International Congresses [ 22, 23]. T+S_5_18.qxp_T+S_2018 28.08.18 13: 50 Seite 16 3 Results and Discussion The main chemical and physical values of this series are presented in Table 1. From the data recorded in this table one can observe the following: (1) The molecular mass presents values between 598 and 686 mass units, which falls in the usual domain of synthetic oils. (2) The density shows a remarkable smooth variation, being a function of the long aliphatic chain brought in by the glycol. However, the high content in isotridecanol radical, long aliphatic chain, sets the fashion of the very clos e value s recorded, and that is in good agreement with theoretical presumptions. In the same time this smooth variation emphasize the high purity level of these complex synthetic esters. (3) The refractive index follows a similar behavior being not able to record, discern, a logical variation. This fact is also explainable, in general, by the high molecular mass of these derivatives and by observing that the variation is due to the content of glycol rest, which has a small weight contribution to the global mass. Refractive index underlines, again, the high level of purity of these products. (4) The dynamic viscosity follows a logical rule which means that it presents progressive increasing values as the length of the glycol used (that is implicitly the aliphatic content) increases. Generally, the values recorded are reasonable small. The values of the physical and rheological characteristics that are important with respect to the tribological properties, are included in Table 2. First of all, one can easily remark the reasonable level recorded for the viscosity index VI, with values ranging from 52 up to 103 .This behavior means a very good de- Aus Wissenschaft und Forschung 17 Tribologie + Schmierungstechnik · 65. Jahrgang · 5/ 2018 Table 1: Values of the representative physical and chemical characteristics Table 2: Representative tribologic parameters Table 3: Four ball test T+S_5_18.qxp_T+S_2018 28.08.18 13: 50 Seite 17 lubricating characteristics, as proved by the four-ball test. By taking into consideration the overall features described above of these special conceptualized absolutely new complex synthetic esters, considered as base oils with biodegradability potential, one can consider that the theoretical premises which have been a priori considered, or the fundamental concepts or principles that grounded the whole program, were fully certified, validated, by the remarkable good level of general properties of these compounds. Acknowledgements Special thanks must be addressed to our former students which graduated from Politehnica Timisoara, Faculty of Chemical Engineering, Prof. Dr.-Eng Waltraut Brandl, Prorector at Gelsenkirchen University, Germany, and to Dr.-Eng Livius Cotarca, Scientific Director, Head of R&D Zambon Group, Italy, respectively, for their valuable support in order to acquire the raw materials used in this work, as well as to Dipl.-Eng Victor Boiangiu Head of Analytic Department at ICERP Institute Ploiesti, Romania, for performing the specific tribological tests. References [1] Schaefer T.G., Esters in Synthetic Lubricants, Forums, “Bob is the Oil Guy”, Science and Technology of Oils and Lubrication Additives, Technical and White Papers, 2017, 01.24, 13 pp. [2] Cavalcanti da Silva J.A. Biodegradable Lubricants and their Production via Chemical Catalysis, Tribology-Lubricants and Lubrication, 2011, October, pp 185-200. [3] Firdovsi Tataroglu Sejidov and Yagoub Mansoori, Esters of oxypropylated trymethylol propanes as synthetic lubricants, Industrial Lubrication and Tribology 2007, 59(1), 12-17; doi: 10.1108/ 00368790710723098 [4] Robiah Yunus et al., Synthesis of Palm Oil Based Trimethylolpropane Esters with Improved Pour Points, Industrial & Engineering Chemistry Research (ACS Publications), 2005, 44 (22), 8178-8183. [5] Schlosberg R.H. et al., Synthetic ester base stocks for low emission lubricants, US Patent, 1997, 5.674.822, October 7. [6] Sundeep G. Shankwalkar, and Douglas G. Placek, Synthetic ester lubricant having improved antiwear properties,US Patent 1996, 5.560.849,October 1. [7] Schick, J.W., and Kaminski, J. M., Synthetic ester and hydrogenated olefin oligomer lubricant and method of reducing fuel consumption therewith, US Patent, 1979, 4.175.047, November 20. [8] Duncan C.B, and Leah K.M., Biodegradable branched synthetic ester base stocks and lubricants formed thereof, US Patent, 1997, 5.681.800, October 28. Aus Wissenschaft und Forschung 18 Tribologie + Schmierungstechnik · 65. Jahrgang · 5/ 2018 pendence, relationship, of the viscosity versus temperature, which generally signifies that temperature has a little influence on the viscosity, and this fact is a basis criterion as regards the choice of a lubricant which has to prove its application versatility. The values recorded for the flash point are also very good, the maximum value registered being 184o C. As for the pour point, the level of this parameter is really excellent, the values are ranging from -52 °C to -58 °C .The complex structure of these derivatives has a substantial contribution for this behavior. To check the lubricity properties of these complex synthetic esters, some four-ball tests were performed, and the results of these measurements are recorded in Table 3. As one can see from this table, when these compounds are evaluated as (simply) base oils, that is without any anti-wear additive, they perform very well, by observing also that the values recorded fall in a homogeneous interval. When additivated, some of the terms show improved values, to a certain extent. One can also remark that they show a good compatibility with the additive system used. 4 Conclusions On the basis of the regular alternation or successive distribution principle of the polar and non-polar chemical functions, equally distributed on the length of a sufficient/ satisfactory long/ large molecule, principle that could be integrated in a so-called myriopod (myriapod) concept, some complex synthetic esters, considered as synthetic base oils with biodegradability potential, built on the basis of malonic acid, isotridecanol, which is considered/ used as an end/ final segment or a capping element, and by using different glycols such as (mono) ethylene, 1,3 propylene, 1,4 butylene,1,5 pentamethylene, 1,6 hexamethylene, diethylene and triethylene glycol, respectively, were synthesized and evaluated as tribological fluids. These absolutely new compounds showed good values for the viscosity index, VI, with values which are ranged from 52 up to 103 units. They also showed good, fair high, values for the flash point, the best value being 184 °C. On the other hand the pour point presents excellent values, all products having pour points around -52 °C, up to -58 °C. On the other hand, this elaborated structure of these complex ensured the capacity to reach a very good level of T+S_5_18.qxp_T+S_2018 28.08.18 13: 50 Seite 18 [9] Carr D.D. and DeGeorge N., Synthetic lubricant base stock of monopentaerythritol and trimethylolpropane esters, US Patent, 1989, 4.826.633, May 2, [10] Jumat Salimon, Nadia Salih and Emad Yousif, Improvement of pour point and oxidative stability of synthetic ester basestocks for biolubricant applications, Arabian Journal of Chemistry, 2012, Vol.5, Issue 2, pp 193-200. [11] Robiah Yunus, Ahmadun Fakhru’l-Razi, Tian Lye Ooi, Sunny E.Yuke and Joseph M.Perez, Lubrication properties of trimethylolpropane esters based on palm oil and palm kernel oils, European Journal of Lipid Science and Technology, 2004, vol 106, issue 1, pp 52-60.; doi.org/ 10.1002/ ejlt.200300862. [12] Sevim Z.Erhan, Brajendra K.Sharma, Zengshe Liu and Atanu Adhvaryu, Lubricant base stock potential of chemically modified vegetable oils, Journal of Agricultural and Food Chemistry (ACS Publications), 2008, vol 56, issue 19, pp 8919-8925, September 11. [13] Xuedong Wu et al, The study of epoxidized rapeseed oil used as a potential biodegradable lubricant, Journal of the American Oil Chemical Society, 2000, Vol 77, issue 5, pp 561-563, May. [14] Mirci L.E., Synthetic complex esters as tribological fluids with biodegradability potential, 2 nd International Conference on Advanced Tribology (iCAT),3-5 December, 2008, Singapore, National University of Singapore, Extended Abstracts, 490-492 [15] Mirci L. E., Synthetic Malonic Biodegradable Lubricants and Method of Obtaining Thereof, RO Patent 2017, 131044, 29.12.2017 [16] Mirci L.E. and Patrut A., Synthetic Adipic Complex Tetraesters as Eco-Friendly Lubricants, Lubrication Science/ Synthetic Lubrication, (John Wiley), (ISI ), 2013, Vol 25, Isue.5,August, p 330-350, DOI Number 10.1002/ ls.1226 [17] Mirci L.E., Patrut A. And Resiga D., New Sebacic Complex Ester Base Oils Lubricants with Biodegradability Potential, Tribologie und Schmierungstechnik, Expertverlag, 2014, ISI, 61 Jahrgang, Heft 2, 2014, pp.. 33-46 [18] Mirci L.E. and Patrut A., Synthetic Adipic Complex Tetra- Esters Base Oils, Tribologie und Schmierungstechnik, Expertverlag, 2014, ISI, 61 Jahrgang, Heft 3, 2014, pag 21-27 [19] Mirci L.E. and Patrut A., Synthetic Complex Sebacic Tetraesters Base Oils Lubricants, Tribologie und Schmierungstechnik, Expertverlag, 2014, ISI, 61 Jahrgang, Heft 4, 2014, pag 12-20 [20] Mirci L.E., Synthetic Biodegradable Ester Lubricant and Method of Obtaining Thereof, RO Patent, 2010, 125100, 20.10.2010. [21] Mirci L.E., Synthetic Sebacic Lubricants and Method of Obtaining Thereof, RO Patent, 129562, 2015, 29.05. 2015 [22] Mirci L.E. and Tamas A., Synthetic Complex Malonic Esters as Eco-Friendly Base Oils, The 20 th International Colloquium Tribology, 2016, (ISI ), Technische Akademie Esslingen, TAE, Stuttgart/ Ostfildern,12-14 January 2016, Poster Session (Synthetic Base Oils), 10 pp CDROM, Abstracts p.207 [23] Mirci L.E. and Bogatu L., Synthetic Complex Malonic Esters as Eco-Friendly Lubricants, 21st International Colloquium Tribology, January 9-11, 2018 (ISI) Technische Akademie Esslingen, TAE, Germania, Suttgart/ Ostfildern, Session Axle Fluids and Hydraulic, 11 January 2018, Room G2, 15,30-16,00, Extended Abstract pg 323 Aus Wissenschaft und Forschung 19 Tribologie + Schmierungstechnik · 65. Jahrgang · 5/ 2018 Hier könnte auch IHRE Firmen-Information zu finden sein! 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