14 Tribologie + Schmierungstechnik 65. Jahrgang 1/ 2018 Aus Wissenschaft und Forschung * Tech licentiate & MSc.Mehdi Fathi-Najafi MSc. Linda Malm Dr. Jinxia Li Nynas AB, Technical Development & Market Support SE-149 82 Nynäshamn Sweden Replacement of Group I; A way forward for the Grease manufacturers M. Fathi-Najafi, L. Malm, J. Li* Eingereicht: 25. 3. 2017 Nach Begutachtung angenommen: 27. 5. 2017 Ersatz von Gruppe I Grundölen; Die Zukunft für Schmierfette Schätzungen zufolge wird die Gesamtproduktion der paraffinischen Gruppe I Grundöle bis zum Jahr 2020 auf etwa 40 % der gesamten Grundölproduktion sinken, und einige schätzen sie sogar auf weniger als 30 % ein. Ungeachtet der Höhe des Rückgangs ist ein ernstzunehmender Effekt dieser Entwicklung, dass das Angebot der Grundölindustrie nicht mehr für die Anforderungen der industriellen Schmiermittel- und Fettindustrie optimiert ist. Die Defizite in der Löslichkeit und Viskosität können nicht einfach durch die hochraffinierten paraffinischen Gruppe II und III Grundöle ersetzt werden. Höhere Polarität und ausreichendes Lösevermögen sind neben den Viskositäten die wichtigsten Parameter für Prozessöle, Metallbearbeitungsflüssigkeiten, Hydrauliköle und Fette. Im Rahmen dieser Arbeit wurde durch präzises Blenden von naphthenischen und paraffinischen Grundölen eine neue Range (NR) von Base Stocks entwickelt, die der paraffinischen Gruppe I Grundölen sehr ähnlich ist. Die Parameter dieser neu entstandenen Grundöle decken sich mit denen zahlreicher etablierter Gruppe I Grundöle, beginnend beim Solvent Neutral 60 bis hin zum Solvent Neutral 600, mit vergleichbarem Anilinpunkt und kinematischer Viskosität sowie verbessertem Stockpunkt. Zur Bestätigung einiger Eigenschaften der neuen Grundöle, wurden verschiedene Vergleichsstudien zur Herstellung herkömmlicher Lithiumfette durchgeführt. Die Wahl fiel auf Lithiumfette, da diese einen Anteil von ca. 55 Prozent aller Schmierfette ausmachen. Die Vergangenheit zeigt, dass diese neuen Grundöle die herkömmliche paraffinische Gruppe I Grundöle in vielen industriellen Anwendungen ersetzen können. Die aktuellen Studien belegen nun, dass auch Schmierfette erfolgreich mit den neuen Grundölen hergestellt werden können. Schlüsselwörter Grundöle, Paraffinöl, Naphthenöl, Schmierfett, Rheologie, Tieftemperatur The total production of paraffinic Group I is estimated to fall to about 40 percent of the total base oil production by the year 2020 and some estimate it down to less than 30 percent. Regardless the degree of the fall, a serious consequence of these changes is that the offering of the base oil industry is no longer optimized for the industrial lubricant and grease industry requirements. The deficits in solvency and viscosity might not be readily substituted by the highly refined paraffinic Group II and Group III base oils. Higher polarity, aromaticity and sufficient solvency power constitutes, beside the viscosities, the most essential parameters for process oils, metal working fluids, hydraulic oils and greases. Within the frame of this work, a new range (NR) of base stocks, very similar to paraffinic Group I, have been developed by carefully blending naphthenic and paraffinic base oils. This new range of base oil is closely matching a broad selection of paraffinic Group I base oils, from Solvent Neutral 60 to Solvent Neutral 600 with retained kinematic viscosity and aniline point, and with improved pour point. In order to verify some of the characteristics of these new base oils some comparative studies have been conducted by making conventional lithium greases. The reason for choosing lithium grease was due to high degree of the representation with the lubricating greases which is around 55 percent. Previous findings emphasized that this new range of base oils may replace conventional paraffinic Group I in various industrial application, and based on this study, the lubricating greases could be added to the list of successful applications. Keywords Base oils, Paraffinic oil, Naphthenic oil, Lubricating grease, Rheology, Low temperature Kurzfassung Abstract T+S_1_18 06.12.17 12: 19 Seite 14 Tribologie + Schmierungstechnik 65. Jahrgang 1/ 2018 1 Introduction The global ongoing rationalization of paraffinic Group I production and its potential impact on the future availability of paraffinic Group I has led several lubricant formulators to start evaluating alternative products. Almost 2 million metric tons of paraffinic Group I capacity disappeared during the last year. The rapid changes in the base oil market, driven mainly by the technical demand from high performance automotive engine oil applications, are impacting all lubricant applications. The viscosity range covered in paraffinic Group I is wider, providing much needed high viscosity to industrial gear oils, greases and engine oils. The solvency offered by paraffinic Group II and Group III, with rapidly increasing aniline points, and lower aromatic carbon type content, is far lower than that of Group I base oils. Thus, some negative effect on the blending of industrial lubricants based on Group II or Group III base oils with existing Group I based industrial product can be foreseen, and have indeed been reported from the field. The worst-case scenario could be a massive reformulation process based on trial errors which of course will be a costly and time-consuming process. Hence, the questions are: Can we escape this reformulation process in the future? Can we hope that we are going to see a new shift back to a rebuilding of paraffinic Group I refineries? The most probable answer to both questions, is NO! Hence, what to do? What is the most cost-efficient way out of this dilemma? We at Nynas believe that due to the long-term availability of paraffinic Group II, Group III and naphthenic oils, it is most probably that a mixture of naphthenic oil with paraffinic Group II and Group III is a realistic, cost effective and fast solution for substitution of paraffinic Group I in various industrial applications. A previous publication [ref] covered some interesting areas such as: - Response of Pour Point Depressant (PPD) - Elastomer compatibility with respect to Nitrile Butadiene Rubber (NBR). - Formulation and characterization of a model hydraulic fluid This paper suggests alternatives, here called NR, that could be used as a replacement to paraffinic Group I grease lubricated applications. More precisely, the behavior of two NR grades (500 & 600) in the conventional lithium grease compared to a paraffinic oil Group I (SN 500) have been studied. Experimental work It is well known that Solvent Neutral 500 (SN 500) is traditionally used for preparation of conventional lithium 15 Aus Wissenschaft und Forschung 3 Characteristics Unit Test method ASTM SN 500 NR 500 NR 600 Appearance Clear & Bright Clear & Bright Clear & Bright Density, 15°C g/ dm 3 D 4052 889.6 889.0 876.0 Viscosity, 40°C mm 2 / s D 445 101 100 120 Viscosity, 100°C mm 2 / s D 445 10.9 10.2 12.6 Viscosity Index mm 2 / s D 2270 91 79 98 Flash Point, PM °C 232 226 250 Refractive Index, 20 °C D 1747 1,488 1.487 1.481 Aniline Point °C D 611 104.3 111 123 Carbon Composition D 2140 C A % 3.8 3 1 C P % 66.7 61 69 C N % 29.5 36 30 IR, C A % 7.8 6 2 Viscosity-Gravity- Constant D 2501 0.821 0.821 0.800 Pour point °C D 97 -12 -21 -15 Sulphur % D 2622 0.944 0.03 0.02 Color rating D 1500 1.7 0.5 1 Copper strip, 100°C/ 3h rating D 130 1 1 1 Total Acid Number mg KOH/ g D 974 <0.01 <0.01 <0.01 As it can be seen in Table 1, NR 500 and 600, in comparison to SN 500, have significantly lower Sulphur content, lower pour point and lighter in color! Thus, it is foreseen that theses improved properties will, in many cases, improve the performance and quality of the fully formulated greases. The grease samples have been prepared in an atmospheric condition in which the base oils described in Table 1 were used. The target consistency for these samples was NLGI grade 2. Notable is that the greases used in this study contain only antioxidant. Table 2. Some properties of the lithium based greases. Based on the measured properties of the greases, shown in Table 2, it can be concluded that all three grease samples show good shear stability despite having different thickener content; sample C (based on NR 600) Table 1: The characteristics of the base oils T+S_1_18 06.12.17 12: 19 Seite 15 16 Tribologie + Schmierungstechnik 65. Jahrgang 1/ 2018 grease which stands for almost 55 percent of the global grease production. Hence, this fluid is used as a reference in comparison with NR 500 and NR 600. The characteristics of these base oils can be seen in Table 1. As it can be seen in Table 1, NR 500 and 600, in comparison to SN 500, have significantly lower Sulphur content, lower pour point and lighter in color! Thus, it is foreseen that theses improved properties will, in many cases, improve the performance and quality of the fully formulated greases. The grease samples have been prepared in an atmospheric condition in which the base oils described in Table 1 were used. The target consistency for these samples was NLGI grade 2. Notable is that the greases used in this study contain only antioxidant. Based on the measured properties of the greases, shown in Table 2, it can be concluded that all three grease samples show good shear stability despite having different thickener content; sample C (based on NR 600) highest and sample B (based on NR 500) the lowest. The oxidation stability test results indicate slightly better performance for Grease A which may be referred to higher Sulphur content of SN 500 that can act as a secondary antioxidant. However, all three products are performing well in this test. The typical criteria for a conventional lithium grease is 5 psi or lower. The most interesting part of this evaluation was to study the impact of significantly better pour point in NR 500 and 600 on the mobility of the greases compared with SN 500 based which has been investigated by measuring both the flow pressure and rheological properties at low temperature. Flow pressure of the lubricating grease, measured according to DIN 51805, is widely recognized method as a relevant way to simulate mobility of the grease in the laboratory. Hence, the flow pressure for the grease samples at various temperatures have been measured, the required pressure for each sample at six different temperatures are shown in Figure 1. The outcome emphasizes excellent performances for the two NR based greases. In fact, Solvent Neutral 500 based grease requires almost three times higher pressure than NR 500 to be mobile. Rheological measurements It is well known that lubricating grease is a viscoelastic material, in other words a material with a viscous part (the base oil) and an elastic part (e. g. the thickener). Pa- Aus Wissenschaft und Forschung 3 500 600 Table 1. The characteristics of the base oils. As it can be seen in Table 1, NR 500 and 600, in comparison to SN 500, have significantly lower Sulphur content, lower pour point and lighter in color! Thus, it is foreseen that theses improved properties will, in many cases, improve the performance and quality of the fully formulated greases. The grease samples have been prepared in an atmospheric condition in which the base oils described in Table 1 were used. The target consistency for these samples was NLGI grade 2. Notable is that the greases used in this study contain only antioxidant. Characteristics Unit Test Method Grease A Grease B Grease C Base oil SN 500 NR 500 NR 600 Thickener content wt.% 7.98 7.48 9.39 Penetration unworked mm -1 ASTM D 217 285 282 278 Penetration (after 60 strokes) mm -1 ASTM D 217 279 279 280 Penetration (after 10 5 strokes) mm -1 ASTM D 217 300 309 305 Dropping point °C IP 396-02 199 200 198 Cu-corrosion rating ASTM D 4048 1b 1a 1a Oxidation stability (Pressure drop) psi ASTM D 942 2 3 3 samples show good shear stability despite having different thickener content; sample C (based on NR 600) Table 2: Some properties of the lithium based greases 4 highest and sample B (based on NR 500) the lowest. The oxidation stability test results indicate slightly better performance for Grease A which may be referred to higher Sulphur content of SN 500 that can act as a secondary antioxidant. However, all three products are performing well in this test. The typical criteria for a conventional lithium grease is 5 psi or lower. The most interesting part of this evaluation was to study the impact of significantly better pour point in NR 500 and 600 on the mobility of the greases compared with SN 500 based which has been investigated by measuring both the flow pressure and rheological properties at low temperature. Flow pressure of the lubricating grease, measured according to DIN 51805, is widely recognized method as a relevant way to simulate mobility of the grease in the laboratory. Hence, the flow pressure for the grease samples at various temperatures have been measured, the required pressure for each sample at six different temperatures are shown in Figure 1. Figure 1. The required flow pressure (mbar) as a function of temperature. The outcome emphasizes excellent performances for the two NR based greases. In fact, Solvent Neutral 500 based grease requires almost three times higher pressure than NR 500 to be mobile. Rheological measurements It is well known that lubricating grease is a viscoelastic material, in other words a material with a viscous part (the base oil) and an elastic part (e.g. the thickener). Parameters such as temperature and shear stress affect the oil and the thickener differently. Hence, mobility of the grease sample under controlled conditions can generate valuable information. For example, storage modulus (G´) or complex modulus (G*) of the grease can be interpreted as the real consistency of the grease, at the applied condition. In an attempt to study the thermal behaviour of the greases the oscillatory program of a rotational rheometer has been used. The first step in the characterisation was to find out the so-called linear viscoelastic region (LVER) by applying a strain sweep program in which the frequency and the temperature were kept constant (10 Hz and 25 °C respectively), and then the strain was increased logarithmically from 0.01 to 1000%, see Figure 2. 1070 1145 370 395 495 645 0 200 400 600 800 1000 1200 1400 1600 -40 -35 -30 -25 -20 -15 -10 -5 0 Flow pressure (mbar) Temprature (°C) Grease A Grease B Grease C rameters such as temperature and shear stress affect the oil and the thickener differently. Hence, mobility of the grease sample under controlled conditions can generate valuable information. For example, storage modulus (G´) or complex modulus (G*) of the grease can be interpreted as the real consistency of the grease, at the applied condition. In an attempt to study the thermal behaviour of the greases the oscillatory pro- Figure 1: The required flow pressure (mbar) as a function of temperature T+S_1_18 06.12.17 12: 19 Seite 16 Tribologie + Schmierungstechnik 65. Jahrgang 1/ 2018 gram of a rotational rheometer has been used. The first step in the characterisation was to find out the so-called linear viscoelastic region (LVER) by applying a strain sweep program in which the frequency and the temperature were kept constant (10 Hz and 25 °C respectively), and then the strain was increased logarithmically from 0.01 to 1000 %, see Figure 2. Figure 2 indicates that grease A (SN 500 based) is slightly thinner (lower G´) and has shorter LVER than Grease B (NR 500 based) and C (NR 600 based) despite of the fact that all three greases have the same NLGI grade. However, the next step in this part of the study was to measure the change of the complex modulus (G*), which is a sum of storage modulus and viscous modulus, over a wide range of temperature while the shear stress (10 Pa) and the frequency (10 Hz) have been kept constant. To conduct this evaluation more accurate it was decided to divide it in two steps; Step 1) the low temperature (from +25 down to -25 °C) and Step 2) the high temperature (from +25 to +120 °C). Step 1): The low temperature behaviour: This type of measurement reveals the degree of stiffness of a grease when the temperature is reduced. Thermal weep program was run from +25 to -25 °C. The obtained data is shown in Figure 3. Figure 4 above reveals preferably information such as: a) Grease A (SN 500 based) shows a faster degree of increased complex viscosity than the others. This increase is accelerating as applied temperature approaches the pour point of the base oil which in turn confirms the poor results from Flow pressure measurements, discussed earlier in this paper. b) Grease B and Grease C show same degree of the thickening effect within the applied temperature range and significantly better performance than Grease A. Step 2: The high temperature behaviour: This type of measurement is targeting the degree of softening of a grease when the temperature is increased. Thermal sweep program was run from +25 to +120 °C. The obtained data, shown in Figure 4, indicates that Grease C (NR 600 based) softens less than the other two greases, most probably due to the higher thickener content. Differential Scanning Calorimetry (DSC) has also been used to investigate the wax formation within the base oils which lightens the reason behind the excellent low temperature mobility of e. g. NR 600 in comparison to SN 500 despite of the fact that they have almost same pour point (-15 °C vs -12 °C). Notable that reproducibility of test method is ±6 °C. The base oils were analyzed with the DSC using the following conditions: 17 Aus Wissenschaft und Forschung Figure 2: Storage modulus (G´) and Viscosity modulus (G´´) vs. Strain for the three grease samples at 25 °C 5 Figure 2. Storage modulus (G´) and Viscosity modulus (G´´) vs. Strain for the three grease samples at 25 °C Figure 2 indicates that grease A (SN 500 based) is slightly thinner (lower G´) and has shorter LVER than Grease B (NR 500 based) and C (NR 600 based) despite of the fact that all three greases have the same NLGI grade. However, the next step in this part of the study was to measure the change of the complex modulus (G*), which is a sum of storage modulus and viscous modulus, over a wide range of temperature while the shear stress (10 Pa) and the frequency (10 Hz) have been kept constant. To conduct this evaluation more accurate it was decided to divide it in two steps; Step 1) the low temperature (from +25 down to -25 °C) and Step 2) the high temperature (from +25 to +120 °C). Step 1) The low temperature behaviour: This type of measurement reveals the degree of stiffness of a grease when the temperature is reduced. Thermal weep program was run from +25 to -25 °C. The obtained data is shown in Figure 3. a) Grease A (SN 500 based) shows a faster degree of increased complex viscosity than the others. 0 100·10 3 200·10 3 300·10 3 400·10 3 500·10 3 600·10 3 700·10 3 Pa G' -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 °C Temperature T Grease A Grease B Grease C Figure 3: Complex modulus vs. temperature at constant shear stress T+S_1_18 06.12.17 12: 19 Seite 17 18 Tribologie + Schmierungstechnik 65. Jahrgang 1/ 2018 Equilibrate at 50 °C; Isothermal at 50 °C for 5 min; Ramp 10 °C/ min down to -120 °C and keeping the sample in isothermal condition at -120 °C for 5 min. The measured cooling profiles for the base oils that can be seen in Figure 5 reveals one possible reason behind the better mobility of the greases based on NR grades compared with SN 500. Figure 5 suggests that the all three base oils contain wax which has been marked with the blue colored box, however, SN 500 shows not only highest wax contain (integral of the curvature part), but also it starts to crystalize at lowest temperature (T onset) in comparison to NR 600 and NR 500. The differences between NR 500 and NR 600 in both pour point and T onset should be addressed to the higher dosage of wax free naphthenic oil in NR 500. Further, it is believed that higher degree of the solvency of the naphthenic oils involved in NR grades also suppress the crystallization temperature. Notable that in number of publications, it has been stated that the pour point of a mineral oil doesn’t reflect the low temperature mobility of an oil or/ and the grease based upon, simply because an oil doesn’t inform “why” the oil stops to flow with the limited of time (5 sec). The lowest flowability of an oil can depend on the wax formation, high viscosity or/ and a combination of both. For example, a wax free oil naphthenic oil will reach its pour point due to an increased viscosity (low Viscosity index) while a paraffinic oil (regardless the group designation) may reach its pour point due to a combination of an increased viscosity and crystallization of the wax in the oil. The first one, naphthenic oil, still behaves as a Newtonian fluid, while the paraffinic one as a non-Newtonian fluid which in turn contributes to high degree of the elasticity to the grease based upon. What above described is quite useful if manufacturers of the lubricating greases looking for reducing the number of the base oils that they usually use. Let’s see how? It’s well known that one of the reasons for using two oils; naphthenic oil and paraffinic oil, in the preparation of a lubricating grease is to improve the low temperature mobility of the finished product but then it requires two different storage capacities and also risk for contamination Aus Wissenschaft und Forschung 6 This increase is accelerating as applied temperature approaches the pour point of the base oil which in turn confirms the poor results from Flow pressure measurements, discussed earlier in this paper. b) Grease B and Grease C show same degree of the thickening effect within the applied temperature range and significantly better performance than Grease A. Step 2: The high temperature behaviour: This type of measurement is targeting the degree of softening of a grease when the temperature is increased. Thermal sweep program was run from +25 to +120 °C. The obtained data, shown in Figure 4, indicates that Grease C (NR 600 based) softens less than the other two greases, most probably due to the higher thickener content. Figure 4. Complex modulus vs. temperature at constant shear stress. Differential Scanning Calorimetry (DSC) has also been used to investigate the wax formation within the base oils which lightens the reason behind the excellent low temperature mobility of e.g. NR 600 in comparison to SN 500 despite of the fact that they have almost same pour point (-15 °C vs -12 °C). Notable that reproducibility of test method is ±6 °C. The base oils were analyzed with the DSC using the following conditions: Equilibrate at 50 °C; Isothermal at 50 °C for 5 min; Ramp 10 °C/ min down to -120 °C and keeping the sample in isothermal condition at -120 °C for 5 min. The measured cooling profiles for the base oils that can be seen in Figure 5 reveals one possible reason behind the better mobility of the greases based on NR grades compared with SN 500. 6 000,0 8 000,0 10 000,0 12 000,0 14 000,0 16 000,0 18 000,0 20 000,0 22 000,0 26 000,0 Pa |G*| 20 30 40 50 60 70 80 90 100 110 120 130 °C Temperature T Grease A Grease B Grease C Figure 4: Complex modulus vs. temperature at constant shear stress 7 however, SN 500 shows not only highest wax contain (integral of the curvature part), but also it starts to crystalize at lowest temperature (T onset ) in comparison to NR 600 and NR 500. Table 3 Pour point and the onset temperature at wax crystallization. The differences between NR 500 and NR 600 in both pour point and T onset should be addressed to the higher dosage of wax free naphthenic oil in NR 500. Further, it is believed that higher degree of the solvency of the naphthenic oils involved in NR grades also suppress the crystallization temperature. Notable that in number of publications, it has been stated that the pour point of a mineral oil doesn’t reflect the low temperature mobility of an oil or/ and the grease based upon, simply because an oil doesn’t inform “why” the oil stops to flow with the limited of time (5 sec). The lowest flowability of an oil can depend on the wax formation, high viscosity or/ and a combination of both. For example, a wax free oil naphthenic oil will reach its pour point due to an increased viscosity (low Viscosity index) while a paraffinic oil (regardless the group designation) may reach its pour point due to a combination of an increased viscosity and crystallization of the wax in the oil. The first one, naphthenic oil, still behaves as a Newtonian fluid, while the paraffinic one as a non-Newtonian fluid which in turn contributes to high degree of the elasticity to the grease based upon. What above described is quite useful if manufacturers of the lubricating greases looking for reducing the number of the base oils that they usually use. Let’s see how? It’s well known that one of the reasons for using two oils; naphthenic oil and paraffinic oil, in the preparation of a lubricating grease is to improve the low temperature mobility of the finished product but then it requires two different storage capacities and also risk for contamination or/ and misunderstanding when a certain amount of one or the other oil has to be charged into the vessel. Hence, by using e.g. NR 500 the identified issues that mentioned above, will be removed, and subsequently a reduction of the cost employment of the base oils will be achieved. Figure 5: The change of the heat flow (W/ g) as a function of temperature (°C) for the base oils 7 Figure 5. The change of the heat flow (W/ g) as a function of temperature (°C) for the base oils Figure 5 suggests that the all three base oils contain wax which has been marked with the blue colored box, however, SN 500 shows not only highest wax contain (integral of the curvature part), but also it starts to crystalize at lowest temperature (T onset ) in comparison to NR 600 and NR 500. Property SN 500 NR 600 NR 500 Pour point (°C) -12 -15 -21 T onset (°C) -14.60 -19.90 -35.49 . The differences between NR 500 and NR 600 in both pour point and T onset should be addressed to the higher dosage of wax free naphthenic oil in NR 500. Further, it is believed that higher degree of the solvency of the naphthenic oils involved in NR grades also suppress the crystallization temperature. Notable that in number of publications, it has been stated that the pour point of a mineral oil doesn’t reflect the low temperature mobility of an oil or/ and the grease based upon, simply because an oil doesn’t inform “why” the oil stops to flow with the limited of time (5 sec). The lowest flowability of an oil can depend on the wax formation, high viscosity or/ and a combination of both. For example, a wax free oil naphthenic oil will reach its pour point due to an increased viscosity (low Viscosity index) while a paraffinic oil (regardless the group designation) may reach its pour point due to a combination of an increased viscosity and crystallization of the wax in the oil. The first one, naphthenic oil, still behaves as a Newtonian fluid, while the paraffinic one as a non-Newtonian fluid which in turn contributes to high degree of the elasticity to the grease based upon. What above described is quite useful if manufacturers of the lubricating greases looking for reducing the number of the base oils that they usually use. Let’s see how? It’s well known that one of the reasons for using two oils; naphthenic oil and paraffinic oil, in the preparation of a lubricating grease is to improve the low temperature mobility of the finished product but then it requires two different storage capacities and also risk for contamination or/ and misunderstanding when a certain amount of one or the other oil has to be charged into the vessel. Hence, by using e.g. NR 500 the identified issues that mentioned above, will be removed, and subsequently a reduction of the cost employment of the base oils will be achieved. Table 3: Pour point and the onset temperature at wax crystallization T+S_1_18 06.12.17 12: 19 Seite 18 Tribologie + Schmierungstechnik 65. Jahrgang 1/ 2018 or/ and misunderstanding when a certain amount of one or the other oil has to be charged into the vessel. Hence, by using e. g. NR 500 the identified issues that mentioned above, will be removed, and subsequently a reduction of the cost employment of the base oils will be achieved. Summary The results suggest that it is indeed possible to reproduce the key features of Group I base oils, and to formulate lubricating greases and other industrial related formulations based on these. The new range of Group I replacement fluids thus offers, besides the significant low temperature mobility, a convenient way around compatibility, solubility and extensive re-formulation issues that industrial lubricant blenders otherwise must conquer when formulating in base oils other than Group I, which will gradually be less readily available in a changing base oil market. By using NR grade for the preparation of lubricating greases, from a supply and capital employment points of view, a leaner manufacturing process will be gained. Reference [1] T. Norrby et.al; Group I Replacement fluids; Tribologie + Schmierungstechnik 64. Jargang.1/ 2017 [2] M. Fathi-Najafi et.al; Low temperature tribology; Eurogrease 201204 [3] www.nynas.com 19 Aus Wissenschaft und Forschung Bestellcoupon Tribologie und Schmierungstechnik „Richtungsweisende Informationen aus Forschung und Entwicklung“ Getriebeschmierung - Motorenschmierung - Schmierfette und Schmierstoffe - Kühlschmierstoffe - Schmierung in der Umformtechnik - Tribologisches Verhalten von Werkstoffen - Minimalmengenschmierung - Gebrauchtölanalyse - Mikro- und Nanotribologie - Ökologische Aspekte der Schmierstoffe - Tribologische Prüfverfahren Bestellcoupon Ich möchte Tribologie und Schmierungstechnik näher kennen lernen. Bitte liefern Sie mir ein Probeabonnement (2 Ausgaben), zum Vorzugspreis von 7 39,-. So kann ich die Zeitschrift in Ruhe prüfen. Wenn Sie dann nichts von mir hören, möchte ich Tribologie und Schmierungstechnik weiter beziehen. Zum jährlichen Abo-Preis von 7 189,- Inland bzw. 7 198,- Ausland. Die Rechnungsstellung erfolgt dann jährlich. Das Jahresabonnement ist für ein Jahr gültig; die Kündigungsfrist beträgt sechs Wochen zum Jahresende. Firma, Abteilung Straße, Nr. Name, Vorname PLZ, Ort Ort/ Datum, Unterschrift: (ggf. Firmenstempel) Coupon an: expert verlag, Abonnenten-Service, Postfach 2020, 71268 Renningen oder per Fax an: (0 71 59) 92 65-20 T+S_1_18 06.12.17 12: 19 Seite 19