Viscosity Index Improvers Research Articles

Effects of Viscosity Index Improver on Morphology and Graphitization Degree of Diesel Particulate Matter

Effects of viscosity index improver on morphology and graphitization degree of diesel particulate matter were investigated. Three lubricating oils with different viscosity were tested and compared in a two cylinder, four stroke, direct injection diesel engine. 5.0 wt. % and 10 wt. % viscosity index improver were added into lubricating oil to improve the viscosity-temperature performance respectively. Transmission Electron Microscope and Raman spectroscopy were employed to analyze the primary particle size distribution and graphitization degree of diesel particles from different lubricating oils. The primary particles size distribution conformed to Gaussian distribution. When the higher viscosity lubricating oil was used, the primary particle boundaries tend to be clearer and the mean diameter is smaller at 1600 rpm and 2200 rpm. As to the graphitization degree, the ratio of the D1 band to G band areas (AD1/AG) increased with the increasing viscosity at 1600 rpm and 2200 rpm, indicating that the graphitization degree was lower when the higher viscosity lubricating oil was used.

Synthesis, characterization, and performance evaluation of N,N‐Dimethylacrylamide–alkyl acrylate copolymers as novel multifunctional additives for lube oil

AbstractThree copolymeric and two homopolymeric additives were synthesized utilizing the C18 alkyl acrylate (C18Ac) and N,N‐dimethylacrylamide (DMAA) monomers. Three additives named as additive 1, additive 2, and additive 3 were synthesized by varying the ratio between C18Ac: DMAA as 1:1, 1:2 and 2:1 respectively by free radical polymerization using AIBN (azobis(isobutyronitrile)) as initiator, whereas additive 4 and additive 5 were the homopolymers of C18Ac and DMAA, respectively. All the synthesized polymers were characterized by FT‐IR (fourier transform infrared spectroscopy), NMR (nuclear magnetic resonance), and GPC (gel permeation chromatography) analysis. Performance evaluation of the copolymers as viscosity index improver (VII), pour point depressant (PPD), antiwear, antifriction, and anticorrosion additives in polyol base oil was done by standard methods. As far as the VII, anti‐wear, antifriction, and anticorrosive properties are concerned, additive 2 revealed best performance; however, none of the above synthesized additives was found to be suitable for PPD activity.

Dodecyl methacrylate and vinyl acetate copolymers as viscosity modifier and pour point depressant for lubricating oil

The article presents application of homo polymer of dodecyl methacrylate (DDMA) and its copolymers with vinyl acetate (VA) as multifunctional additives for lubricant formulation. Homo polymer of DDMA and five copolymers of DDMA with VA at different molar ratios were synthesized by free radical polymerization method using azobisisobutyronitrile (AIBN) as initiator. The characterization of the polymers was carried out through FTIR, NMR and GPC (gel permeable chromatography) analysis. The performance of all the polymers as viscosity index improver (VII) or viscosity modifier and pour point depressant (PPD) additive in two different base oils (mineral) were evaluated. The mechanism of action of the polymers as pour point depressant was studied by photo micrographic analysis. Rheological study of the formulated lubricant was also carried out and reported. The thermal stability of the polymers was determined by thermogravimetric analysis (TGA). It was found that thermal stability, VI and molecular weights of copolymers are higher than the homopolymer which showed better PPD property.

Using Pyrene Excimer Fluorescence To Probe the Interactions between Viscosity Index Improvers and Waxes Present in Automotive Oil

A new methodology based on pyrene excimer fluorescence (PEF) was applied to quantitatively measure the actual level of intermolecular association between ethylene–propylene (EP) copolymers in toluene in the presence of wax, an intrinsic component of engine oils. EP copolymers are commonly used as viscosity index improvers (VIIs) in engine oils. Unfortunately, waxes in engine oils thicken the oil and are suspected of associating with VIIs at low temperature. In this study, four EP copolymers were maleated to yield EP-MA and then fluorescently labeled with 1-pyrenemethylamine to yield Py-EP. Successful maleation and pyrene labeling were confirmed by Fourier transform infrared (FTIR) and UV–vis absorption spectroscopy. The solution behavior of the EP copolymers in the presence of wax was characterized by PEF, which was used to quantitatively measure the molar fraction of intermolecular interactions (finter) between EP copolymers in the absence or presence of wax. The fraction finter was determined through th...

Thermal analysis of hydrodynamic lubricated journal bearings in internal combustion engines

Hydrodynamic journal bearings are essential components in the internal combustion engines. The prediction of their reliability, durability, and economy, and also of their friction loss power and wear, are of highest importance. For an appropriate representation of the hydrodynamic load-carrying capacity and also the friction behavior, the multibody dynamics of the contacting components, the shape of the contacting component surfaces, the amount of the available lubricant, and the properties of the lubricant itself are of importance. A Reynolds-averaged equation with laminar flow conditions in combination with a dry asperity contact model and a multibody dynamic simulation of the structural components is a typical modeling approach for that purpose. Furthermore, this paper shows a newly developed model for the temperature distribution in the lubricant and the bearing structures. It includes thermal interface conditions between these domains, which incorporates the asperity energy source and predicts the temperature in supply areas. The presented method is applied for a typical engineering task of a sensitivity analysis for oils with different viscosity index improvers in a main bearing of a four-cylinder inline diesel engine. The influence of the oil film temperature on the oil film viscosity and, therefore, on the load-carrying capacity is shown. Furthermore, the simplified two-dimensional approach is compared with a three-dimensional approach in terms of the obtained result. The presented results show similar accuracy of the two-dimensional approach compared to the equivalent three-dimensional case.

Life cycle assessment of waste strategies for used lubricating oil

The study aimed to evaluate the environmental impacts of used lubricating oil (ULO) recovery in the largest oil consumer country in Africa, Egypt. The main questions were: What are the impacts of the different waste management strategies for the recovery of used lubricating oil and which waste management strategy is more eco-friendly? Life cycle assessment (LCA) was employed to model the environmental impacts of the two waste management approaches for used lubricating oil recovery in Egypt: recycling by re-firing and recovery by co-firing. The model was applied to assess the impacts of one of the largest ULO recovery units in the Middle East and North Africa (MENA) region and the only operating unit in Egypt. The following impact categories were included: global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), carcinogens potential (CP), ecotoxicity potential (ETP), respiratory inorganic formation potential (RIFP), respiratory organic formation potential (ROFP), radiation potential (RP), ozone layer depletion (OLD), mineral depletion (MD), land use (LU) and fossil fuel depletion (FFD). Results indicated that recycling by re-refining strategy is more environment-friendly. De-asphalting, de-aromatization and de-waxing processes are the main processes that affect the environmental impacts of lubricating oil production in both strategies, due to the use of hazard materials and toxic solvents in these processes. Fuel gas and fuel oil used as a fuel in the refinery and power units are the main contributors affecting the environmental impacts in case of recycling by re-refining strategy. The highest impacts were detected on FFD, followed by RIFP, GWP, AP, EP, ETP and CP in both strategies; no impacts were detected on RP, OLD and MD. It can be concluded that recycling by re-refining of ULO is the more eco-friendly approach. This strategy is more energy conservative, saves a diminishing fossil fuel resource and reduces burdens on the environment. ULO containing high percentages of additive remnants such as viscosity index improvers and pour point depressants which represents a valuable resource and its proper management should be given the most attention.

Trends in Thermoresponsive Behavior of Lipophilic Polymers

In an effort to find correlations between size changes with temperature of lipophilic polymers in solution and viscosity index trends, the determination of the size of thermoresponsive polymers of various architectures (linear, comb-like, star, and hyperbranched) using two experimental techniques under infinite dilution conditions (0.5% w/w) – dynamic light scattering and small angle neutron scattering, and predictive molecular dynamics simulations is described herein. Viscosity index is an important parameter for lubricants and other rheological applications. The aim of this work was to predict polymer behavior as viscosity index improvers (VIIs) using tools which require minimal amounts of material, as opposed to measuring kinematic viscosities, which require multigram quantities. There were no significant correlations between changes in polymer size with temperature and viscosity index (VI). The polymers with the highest VI (polyalkyl methacrylate - PAMA and Star PAMA) had polar backbones in contrast t...

Terpolymers based on sunflower oil/alkyl acrylate/styrene as sustainable lubricant additive

Five terpolymers consisting of an alkyl acrylate (octyl acrylate/decyl acrylate/dodecyl acrylate), sunflower oil and styrene in different ratios (w/w) viz. 1:1:1, 2:1:1 and 3:1:1 were synthesized by free radical polymerization method using azobisisobutyronitrile (AIBN) initiator in toluene solvent. The polymers were characterized by FT-IR and NMR spectroscopy. Molecular weight of the prepared polymers was determined by gel permeation chromatography (GPC) method. Thermal stability of the polymers was determined by thermogravimetric analysis (TGA). Performance of the prepared polymers as viscosity modifier (VM), also known as viscosity index improver (VII), pour point depressant (PPD) and antiwear in different base oils were evaluated according to standard ASTM methods. Photo micrographic image were used to study the action mechanism of the additives as PPD. Biodegradability of all the polymers was tested through disc diffusion method. From the experimental results, it was observed that the ratio 2:1:1 is most effective for the preparation of terpolymers based on acrylate, sunflower oil and styrene. Moreover, it is also observed that efficiencies as VII and antiwear increase but PPD decrease with increasing the alkyl chain length of the prepared polymers.

Crystallization and Pour Point of Solutions of the Dispersant Poly(Styrene-Co-Methacrylate) Viscosity Modifiers in Lubricating Base Oil

ABSTRACTDispersant viscosity index improvers were synthesized by free radical copolymerization of N,N-dimethylaminoethyl methacrylate (DMAEMA), dodecyl methacrylate, octadecyl methacrylate, and styrene in solution of mineral base oil. Studies included the dependence of the pour point and low-temperature crystallization behavior (characteristic temperatures and enthalpies) of the solutions of these polymer viscosity modifiers (VMs) on the amount of dispersant comonomer, DMAEMA, in the copolymer, weight average molecular weight of the copolymer, and concentration of the polymer in oil. Incorporation of dispersant comonomer in poly(styrene-alkyl methacrylate) structure additionally decreases the pour point of its solutions even for a very small concentration: the pour point of the base oil reduces from −9 to −25°C and −33°C for the 0.1 and 0.5 wt% concentrations of polymer, respectively. For concentrated 50 wt% solutions the enthalpy of crystallization decreases linearly with a decrease in the long-chain alkyl methacrylate share in copolymer. There is no unambiguous correlation between the pour point and crystallization parameters of semidiluted and diluted polymer solutions obtained by differential scanning calorimetry.

Multifunctional lube oil additives based on maleic anhydride

ABSTRACTCopolymer of maleic anhydride with 1-decene was synthesized by using azobisisobutyronitrile as an initiator in toluene solvent and the prepared copolymer was reacted separately with different long chain amines (n-octyl amine, n-decyl amine, and n-dodecyl amine) to get three copolymers. The performance of the polymers in different base oils was evaluated as viscosity modifier (VM) also called viscosity index improver, pour point depressant (PPD), and dispersant by standard ASTM methods. The molecular weight of the polymers was determined by gel permeation chromatography. The TGA value was determined by the standard ASTM method. It was found that the efficiency of the polymers as a VM and dispersant increases with increasing the molecular weight of the polymers as well as with increasing the alkyl chain length. However, the efficiency as a PPD increases with decreasing molecular weight of the prepared polymers and with the decreasing the alkyl chain length.

Biodegradable multifunctional additives for lube oil: Synthesis and characterization

ABSTRACTHomopolymers of isodecyl acrylate and isooctyl acrylate and copolymers of each of them with β-pinene (BP) were synthesized and characterized by spectral, thermogravimetric, and gel permeation chromatographic analysis. Pour point depressant (PPD) and viscosity index improver (VII) properties were tested with additive-doped base oil in terms of pour point (PP) and viscosity index (VI), respectively. Although the isodecyl acrylate polymers were thermally more stable than the isooctyl acrylate polymers, the latter showed higher VI and PPD efficiency. VI and PP values of the additive-doped base oils depend on the nature of mineral base oils as well as on the type and concentration of VII. In addition, introduction of BP moiety in the acrylate backbone has induces excellent biodegradability in the above polymers.

Oleic acid based polymeric flow improvers for Langhnaj (North Gujarat, India) crude oil

This research article investigates the effect of polymeric flow improvers (FI) as pour point depressants (PPD) and rheological property improvers of waxy crude oil in Langhnaj, North Gujarat (India), since application of FI is a more economically viable option for crude oil transportation. Three new comb-shaped copolymers of maleic anhydride and n-alkyl oleate were synthesized by free radical solution polymerization, which were consequently reacted with hexadecyl amine to get poly (hexyl oleate-co-hexadecyl maleimide-co-n-alkyl oleate). Synthesized polymers were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Gel Permeation Chromatography (GPC). These FIs were further evaluated for their pour point depression property and rheology modifier with and without additive using Fann Viscometer. The prepared FIs act as effective pour point depressants as well as viscosity index improvers.

Derivation of two-dimensional non-Newtonian Reynolds equation and application to power-law film slider bearings: Rabinowitsch fluid model

Newtonian lubricants blended with additives (polymer-thickened oils, viscosity index improver, polyisobutylene, etc.) display non-Newtonian dilatant and pseudo-plastic properties. Based upon the Rabinowitsch fluid model, a nonlinear non-Newtonian Reynolds equation has been derived for the study of sliding bearings, in which the general two-dimensional film profile is h = h(x,y,t). Several special cases can be recovered from the present derivation. A steady power-law curved film slider bearing with Rabinowitsch fluids is illustrated. First-order solutions of bearing performances are obtained and discussed through the variation of the nonlinear parameter, the film shape index and the inlet-outlet height ratio.

Effect of Molecular-Scale Features on the Polymer Coil Size of Model Viscosity Index Improvers

Temperature-induced changes in coil size have been proposed as a mechanism underlying the functionality of viscosity index improving polymers. Here, molecular dynamics simulations are used to characterize the effect of temperature on the coil size of model additive polymers. The simulations reproduce experimental observations, where only some polymers increase in size with increasing temperature. The results also reveal that the presence of oxygen atoms in the polymer structure is a key factor in determining whether the polymer expands or contracts. This new simulation approach provides a general methodology for investigating temperature-induced coil size changes in polymeric lubricant additives.

Effects of star‐shaped poly(alkyl methacrylate) arm uniformity on lubricant properties

ABSTRACTStar‐shaped poly(alkyl methacrylate)s (PAMAs) were prepared and blended into an additive‐free engine oil to assess the structure–property relationship between macromolecular structure and lubricant performance. These additives were designed with a comparable number of repeating units per arm and the number of arms was varied between 3 and 6. Well‐defined star‐shaped PAMAs were synthesized by atom transfer radical polymerization (ATRP) via a core‐first strategy from multi‐functional head‐groups. Observations of the polymer‐oil blends suggest that stars with less than four arms are favorable as a viscosity index improver (VII), and molecular weight dominates viscosity‐related effects over other structural features. Star‐shaped PAMAs, as oil additives, effectively reduce the friction coefficient in both mixed and boundary lubrication regime. Several analogs outperformed commercial VIIs in both viscosity and friction performance. Increased wear rates were observed for these star‐shaped PAMAs in the boundary lubrication regime suggesting pressure‐sensitive conformations may exist. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43611.

Practical Application of CO2 as a Viscosity Index Improver for Lubricants

AbstractIn terms of reducing power losses and ensuring optimal lubrication, a high viscosity index is crucial for lubricants exposed to changing load or temperature conditions. Several studies suggest that an enormous improvement of the viscosity‐temperature characteristics could be achieved by the application of dissolved CO2 on various base oils. The direct link between the applied pressure and the lubricant viscosity offers the possibility of adjustable and thus tunable lubricants. The practical implementation of dissolved CO2 as a viscosity index improver is investigated on a roller bearing test rig. The results indicate a significant reduction of power losses and show that it is possible to influence the friction condition in the rolling contact through viscosity adaptation.

Probing the molecular design of hyper-branched aryl polyesters towards lubricant applications.

We report novel polymeric materials that may be used as viscosity index improvers (VII) for lubricant applications. Our efforts included probing the comb-burst hyper-branched aryl polyester architecture for beneficial viscosity and friction behavior when utilized as an additive in a group I oil. The monomer was designed as to undergo polymerization via polycondensation within the architectural construct (AB2), typical of hyperbranched polymers. The monomer design was comprised of aliphatic arms (12 or 16 methylenes) to provide the necessary lipophilicity to achieve solubility in a non-polar medium. Once polymerized, via catalyst and heat, the surface alcohols were functionalized with fatty acids (lauric and palmitic). Controlling the aliphatic nature of the internal arms and peripheral end-groups provided four unique flexible polymer designs. Changing the reaction time and concentration provided opportunities to investigate the influence of molecular weight and branching density on oil-solubility, viscosity, and friction. Oil-solubility was found to decrease with fewer internal carbons, but the number of internal carbons appears to have little influence on the bulk solution viscosity. At concentrations of 2 wt % in a group I base oil, these polymer additives demonstrated an improved viscosity index and reduced friction coefficient, validating the basic approach.

Dual functional star polymers for lubricants

Star-shaped poly(alkyl methacrylate)s (PAMAs) with a 3-arm architecture were designed, prepared and their performance as a dual additive (viscosity index improver and friction modifier) for engine oils was evaluated.

Lipoate Ester Multifunctional Lubricant Additives

Seven lipoate esters were synthesized by esterification of lipoic acid with different structures of alcohols in the presence of a solid acid catalyst and without solvent. The esters were obtained in good yield, characterized using 1H NMR and GPC; and their physical properties investigated. Four of the seven lipoate esters, with good solubility in high oleic sunflower oil (HOSuO) and polyalphaolefin (PAO6) base oils, were further investigated for their lubricant additive property. Additive properties were investigated in HOSuO base oil by varying the additive concentrations in the range 0–20 (w/w %). Properties investigated include: density; kinematic and dynamic viscosity; viscosity index (VI); oxidation stability from onset and peak oxidation temperatures on a PDSC; 4-ball antiwear (AW); and 4-ball extreme pressure (EP). Neat lipoate esters displayed high oxidation stability and high VI. As additives to HOSuO base oil, lipoate esters displayed good viscosity index improver (VII), good antioxidant, good e...

Prediction of fuel economy performance of engine lubricants based on laboratory bench tests

Due to increasingly strict vehicle emissions limitations over the past two decades, fuel economy improvement continues to be a focal point in all aspects of engine and vehicle engine and operation. This paper describes a methodology to predict the quantitative influences of lubricant properties on CEC L-54-96 standard engine fuel economy test. High shear viscosities were measured by means of a Ravenfield Viscometer (Method ASTM D 4741), the boundary friction coefficient was measured at 100°C by means of a High Frequency Reciprocating Rig and traction coefficient was measured at 100°C by means of a Mini Traction Machine in a configuration ball-on-disk. Multiple linear regression procedure was used and an excellent correlation was obtained between measured and predicted fuel economy increment. Both the predictive equation and the diagram of sectors obtained in this work will be very useful in practice to calibrate the real role played by base stock, viscosity index improvers and friction modifiers in the development of new lubricants labeled as fuel economy.