Special Issue "Additives for Lubricants"

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A special issue of Lubricants (ISSN 2075-4442).

Deadline for manuscript submissions: closed (20 November 2013)

Special Issue Editors

Guest Editor
Prof. Dr. James E. Krzanowski (Website)

Mechanical Engineering Department, University of New Hampshire, Kingsbury Hall, 33 Academic Way, Durham, NH 03824, USA
Phone: 1-603-862-2315
Fax: +1 603 862 1865
Interests: nitrides; carbides; sputter deposition; ion-assisted deposition; wear; friction; tool coatings
Guest Editor
Prof. Dr. Boris Zhmud (Website)

Applied Nano Surfaces, Knivstagatan 12, SE-75323 Uppsala, Sweden
Phone: +46 70 9371310
Interests: lubricant formulations (engine oils, metalworking emulsions); solubility and lubricity issues; additives and surface chemistry

Special Issue Information

Dear Colleagues,

Neither mineral nor synthetic base oils can satisfy today’s lubricant performance requirements without using additives. Additives are chemical substances, in most part synthetic, which are used in lubricant formulations to adjust a broad of spectrum of properties by enhancing what is desired and suppressing what is unwanted. Many additives are multifunctional products that may exhibit synergistic or antagonistic behavior when mixed together. As a rule of thumb, additives do not add. This makes balancing and optimization of additive systems a challenging task.

The increasing focus on energy efficiency and environmental safety of lubricants poses new challenges for lubricant formulators, preventing or restricting the use of certain time-proven chemistries, such as ZDDP in engine oil or boric acid in MWF formulations. At the same time, it stimulates the search for new classes of additives, including all-organic ashless friction modifiers, nano-additives, and bio-based superlubricity additives, as well as fundamental studies into how individual additives work.

This special issue will examine current advances and future trends in lubricant additives. Contributions are solicited both from academic researchers working in the field of tribology and lubrication science and their industrial peers dealing with additive adpack development and lubricant formulation. The idea is to promote bi-directional information exchange whereby some practical challenges faced by lubricant industry are presented to university researchers and novel additive chemistries are exposed to industrial researchers and formulators involved in product development.

Prof. Dr. James E. Krzanowski
Dr. Boris Zhmud
Guest Editors

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Lubricants is an international peer-reviewed Open Access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. For the first couple of issues the Article Processing Charge (APC) will be waived for well-prepared manuscripts. English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections.


Keywords

  • lubricant additives
  • friction modifiers
  • superlubricity
  • additive chemistry
  • synthetic oils

Published Papers (8 papers)

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Research

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Open AccessCommunication The Application of Molecular Dynamics in Fullerene-Based Journal Bearing Simulation
Lubricants 2014, 2(1), 1-10; doi:10.3390/lubricants2010001
Received: 20 December 2013 / Revised: 8 January 2014 / Accepted: 10 January 2014 / Published: 24 February 2014
PDF Full-text (625 KB) | HTML Full-text | XML Full-text
Abstract
The article is devoted to modeling of the molecular microscopic journal bearing. The walls and the lubricant of the bearing are fullerene-like molecules. On the basis of similarity theory and analysis of the dimensions, the similarity criterion is proposed. This criterion characterizes [...] Read more.
The article is devoted to modeling of the molecular microscopic journal bearing. The walls and the lubricant of the bearing are fullerene-like molecules. On the basis of similarity theory and analysis of the dimensions, the similarity criterion is proposed. This criterion characterizes the convergence of a numerical solution. The test calculation is also made to evaluate the quality of the proposed criterion. Full article
(This article belongs to the Special Issue Additives for Lubricants)
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Open AccessArticle On the Interactions of Additives in Metalworking Fluids with Metal Surfaces
Lubricants 2013, 1(4), 75-94; doi:10.3390/lubricants1040075
Received: 4 September 2013 / Revised: 27 September 2013 / Accepted: 8 October 2013 / Published: 15 November 2013
Cited by 3 | PDF Full-text (2173 KB) | HTML Full-text | XML Full-text
Abstract
Metalworking fluids (MWF) play a significant role in manufacturing processes, such as machining or forming. Consequently, a high number of MWF with varying chemical composition are commercially available. However, the working mechanisms of the MWF are still object of discussion in science [...] Read more.
Metalworking fluids (MWF) play a significant role in manufacturing processes, such as machining or forming. Consequently, a high number of MWF with varying chemical composition are commercially available. However, the working mechanisms of the MWF are still object of discussion in science and application. This paper addresses the possible interactions of additives with metal surfaces taking the characteristic conditions in machining and forming processes as well as the chemical properties of the surface and the additives into account. The new model for possible interaction of additives with the metal surface is considered and supported by experimental data. This new model does not imply reaction layers as tribological active layer anymore. Full article
(This article belongs to the Special Issue Additives for Lubricants)
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Open AccessArticle Interaction between Lubricants Containing Phosphate Ester Additives and Stainless Steels
Lubricants 2013, 1(2), 48-60; doi:10.3390/lubricants1020048
Received: 6 April 2013 / Revised: 16 April 2013 / Accepted: 25 April 2013 / Published: 17 May 2013
Cited by 5 | PDF Full-text (4252 KB) | HTML Full-text | XML Full-text
Abstract
One way to improve fuel efficiency in today’s jet aircraft engines is to create an environment for higher operating temperatures and speeds. New and improved lubricants and bearing materials must be developed to remain stable in these elevated operating temperatures. Three lubricants, [...] Read more.
One way to improve fuel efficiency in today’s jet aircraft engines is to create an environment for higher operating temperatures and speeds. New and improved lubricants and bearing materials must be developed to remain stable in these elevated operating temperatures. Three lubricants, with varying amounts of tricresyl phosphate added as an anti-wear/extreme pressure additive were tested on two different stainless steels at varying temperatures ranging from 300 °C to 350 °C in vacuum. Significant decomposition of the lubricant base-stocks and the phosphate ester additive did occur in most of the trials resulting in the formation of carboxylic acids and phenols. In these cases a film containing phosphorus was deposited onto the stainless steel substrate. Full article
(This article belongs to the Special Issue Additives for Lubricants)
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Review

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Open AccessReview Graphite and Hybrid Nanomaterials as Lubricant Additives
Lubricants 2014, 2(2), 44-65; doi:10.3390/lubricants2020044
Received: 3 January 2014 / Revised: 3 March 2014 / Accepted: 7 March 2014 / Published: 24 April 2014
Cited by 6 | PDF Full-text (1457 KB) | HTML Full-text | XML Full-text
Abstract
Lubricant additives, based on inorganic nanoparticles coated with organic outer layer, can reduce wear and increase load-carrying capacity of base oil remarkably, indicating the great potential of hybrid nanoparticles as anti-wear and extreme-pressure additives with excellent levels of performance. The organic part [...] Read more.
Lubricant additives, based on inorganic nanoparticles coated with organic outer layer, can reduce wear and increase load-carrying capacity of base oil remarkably, indicating the great potential of hybrid nanoparticles as anti-wear and extreme-pressure additives with excellent levels of performance. The organic part in the hybrid materials improves their flexibility and stability, while the inorganic part is responsible for hardness. The relationship between the design parameters of the organic coatings, such as molecular architecture and the lubrication performance, however, remains to be fully elucidated. A survey of current understanding of hybrid nanoparticles as lubricant additives is presented in this review. Full article
(This article belongs to the Special Issue Additives for Lubricants)
Open AccessReview Lubricants for Metal Belt Continuously Variable Transmissions
Lubricants 2014, 2(1), 11-20; doi:10.3390/lubricants2010011
Received: 4 December 2013 / Revised: 9 January 2014 / Accepted: 10 January 2014 / Published: 25 February 2014
PDF Full-text (1931 KB) | HTML Full-text | XML Full-text
Abstract
This paper reviews the effects of lubricant additives and base stock used in metal belt continuously variable transmissions (CVT) fluids on the CVT transmission torque capacity. Additive formulation composed of phosphorus anti-wear agent, calcium detergent, and dispersant improved the friction coefficient between [...] Read more.
This paper reviews the effects of lubricant additives and base stock used in metal belt continuously variable transmissions (CVT) fluids on the CVT transmission torque capacity. Additive formulation composed of phosphorus anti-wear agent, calcium detergent, and dispersant improved the friction coefficient between the metals. The analysis on the post-test surface suggests that the friction behavior strongly depends on the local morphology of the tribofilms derived from lubricant additives. Examining the effect of base stock on the torque capacity in actual belt CVTs revealed that SN (synthetic naphthene) exhibited 10% higher torque capacity than that of PAO (polyalphaolefin). It is believed that the difference in the torque capacity is due to the difference in the oil-film shearing force generated by the relative sliding between the belt and pulley. Full article
(This article belongs to the Special Issue Additives for Lubricants)
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Open AccessReview Lubricants in Pharmaceutical Solid Dosage Forms
Lubricants 2014, 2(1), 21-43; doi:10.3390/lubricants2010021
Received: 18 December 2013 / Revised: 21 January 2014 / Accepted: 24 January 2014 / Published: 25 February 2014
Cited by 9 | PDF Full-text (264 KB) | HTML Full-text | XML Full-text
Abstract
Lubrication plays a key role in successful manufacturing of pharmaceutical solid dosage forms; lubricants are essential ingredients in robust formulations to achieve this. Although many failures in pharmaceutical manufacturing operations are caused by issues related to lubrication, in general, lubricants do not [...] Read more.
Lubrication plays a key role in successful manufacturing of pharmaceutical solid dosage forms; lubricants are essential ingredients in robust formulations to achieve this. Although many failures in pharmaceutical manufacturing operations are caused by issues related to lubrication, in general, lubricants do not gain adequate attention in the development of pharmaceutical formulations. In this paper, the fundamental background on lubrication is introduced, in which the relationships between lubrication and friction/adhesion forces are discussed. Then, the application of lubrication in the development of pharmaceutical products and manufacturing processes is discussed with an emphasis on magnesium stearate. In particular, the effect of its hydration state (anhydrate, monohydrate, dihydrate, and trihydrate) and its powder characteristics on lubrication efficiency, as well as product and process performance is summarized. In addition, the impact of lubrication on the dynamics of compaction/compression processes and on the mechanical properties of compacts/tablets is presented. Furthermore, the online monitoring of magnesium stearate in a blending process is briefly mentioned. Finally, the chemical compatibility of active pharmaceutical ingredient (API) with magnesium stearate and its reactive impurities is reviewed with examples from the literature illustrating the various reaction mechanisms involved. Full article
(This article belongs to the Special Issue Additives for Lubricants)
Open AccessReview Phosphate Esters, Thiophosphate Esters and Metal Thiophosphates as Lubricant Additives
Lubricants 2013, 1(4), 132-148; doi:10.3390/lubricants1040132
Received: 19 November 2013 / Revised: 10 December 2013 / Accepted: 13 December 2013 / Published: 18 December 2013
Cited by 5 | PDF Full-text (538 KB) | HTML Full-text | XML Full-text
Abstract
Phosphate esters, thiophosphate esters and metal thiophosphates have been used as lubricant additives for over 50 years. While their use has been extensive, a detailed knowledge of how they work has been a much more recent development. In this paper, the use [...] Read more.
Phosphate esters, thiophosphate esters and metal thiophosphates have been used as lubricant additives for over 50 years. While their use has been extensive, a detailed knowledge of how they work has been a much more recent development. In this paper, the use of phosphate esters and thiophosphate esters as anti-wear or extreme pressure additives is reviewed with an emphasis on their mechanism of action. The review includes the use of alkyl phosphates, triaryl phosphates and metal containing thiophosphate esters. The mechanisms of these materials interacting with a range of iron and steel based bearing material are examined. Full article
(This article belongs to the Special Issue Additives for Lubricants)

Other

Jump to: Research, Review

Open AccessTechnical Note Nanomaterials in Lubricants: An Industrial Perspective on Current Research
Lubricants 2013, 1(4), 95-101; doi:10.3390/lubricants1040095
Received: 17 September 2013 / Revised: 28 October 2013 / Accepted: 14 November 2013 / Published: 20 November 2013
Cited by 5 | PDF Full-text (706 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an overview on the use of various classes of nanomaterials in lubricant formulations. The following classes of nanomaterials are considered: fullerenes, nanodiamonds, ultradispersed boric acid and polytetrafluoroethylene (PTFE). Current advances in using nanomaterials in engine oils, industrial lubricants and [...] Read more.
This paper presents an overview on the use of various classes of nanomaterials in lubricant formulations. The following classes of nanomaterials are considered: fullerenes, nanodiamonds, ultradispersed boric acid and polytetrafluoroethylene (PTFE). Current advances in using nanomaterials in engine oils, industrial lubricants and greases are discussed. Results of numerous studies combined with formulation experience of the authors strongly suggest that nanomaterials do indeed have potential for enhancing certain lubricant properties, yet there is a long way to go before balanced formulations are developed. Full article
(This article belongs to the Special Issue Additives for Lubricants)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Type of Paper: Review
Title: Lubricant additive technology for continuously variable transmissions
Authors: Keiichi Narita
Affiliations: Lubricants Research Laboratory, Idemitsu Kosan Co.,Ltd.
Abstract: This paper sought to examine the effect that the additives and base stock used in the metal belt CVT oil have on the CVT transmission torque capacity.
An additive formulation consisting of a combination of a phosphorus anti-wear additive, a calcium detergent, and dispersant improved the friction coefficient between the metals. The results of the surface analysis of the friction surface indicate that a substance, presumed to be calcium compounds, formed a film exhibiting small islands. Because this film is rougher, it is assumed there is a high friction coefficient.
By further adding a sulfur extreme pressure agent, it became possible to improve the anti-seizure properties while maintaining a high friction coefficient.
Examining the effect base stock has on the transmission torque capacity of actual belt CVTs revealed that SN (synthetic naphthene) exhibited a 10% higher torque capacity than that of PAO (polyalphaolefin). It is believed that the difference in the torque capacity is due to the difference in the oil-film shearing force generated by the relative sliding between belt and pulley.

Type of Paper: Research Paper
Title: Diamond-Like Carbon Introduced by Novel Silicate Based Lubricant Additive
Authors: Jing Zhang
Affiliations: Indiana University – Purdue University Indianapolis, Indiana 46202, USA
Abstract (around 100 words): Diamond-Like Carbon (DLC) was observed with the application of a novel silicate based lubricant additive. The tribological properties of the pin-disk pair is studied using a new designed pin-on-disk tester. With the application of the additive, the coefficient of friction was reduced by ~40%. SEM and XRD examinations showed that a smooth and high C-content outer layer was formed on the specimen surfaces, suggesting formation of diamond-like carbon (DLC) film. Using nano-hardness measurements, the hardness of the layer on the disk and the pin were 10.2 GPa and 16.7 GPa respectively. Wear loss and ferrographic analyses indicated that a “negative wear” occurred when the additive was applied, suggesting the debris particles were captured by the specimen to form the self-repaired restoration layer.

Type of Paper: Review
Title: Lubricants: Its Application in the Pharmaceutical-Solids
Authors: Jinjiang Li and Yongmei Wu
Affiliation: Drug Product Science and Technology, Bristol-Myers Squibb Co., New Brunswick, NJ 08903, USA
Abstract: Lubrication is a key parameter for a successful manufacturing in pharmaceutical operations and lubricants are the essential ingredients in formulation development to achieve this. Although many unsuccessful manufacturing operations are caused by the issues related to lubrication, in general, lubrication is not considered a very challenging step in drug development. In this paper, first, a fundamental background on lubrication will be reviewed, in which the relationships between lubrication and friction-adhesion will be discussed. Then, the application of lubrication in pharmaceutical product development and manufacturing process will be discussed: the lubrication in powder blending, roller compaction, and tabletting. In addition, the characteristics of commonly used pharmaceutical lubricants will be summarized. Furthermore, some case studies on the impact of lubricants on pharmaceutical operation and product performance will be provided. Finally, we will present some perspectives on the development of new lubricants in the pharmaceutical industry in the future.

Type of Paper: Review
Title: Phosphate Esters as Lubricant Additives
Authors: David W. Johnson and John E. Hils
Affiliations: Department of Chemistry, University of Dayton, 300 College Park, Dayton, OH 45469-2357, USA
Abstract: Phosphate esters have been used as lubricant additives for over 50 years. While their use has been extensive, the knowledge of how they work has been much more recent. In this paper, the use of phosphate esters as anti-wear or extreme pressure additives is reviewed with an emphasis on their mechanism of action. The mechanisms of these materials interacting with a wide range of substrates are examined. The review includes the applications of trialkyl phosphates and triaryl phosphates.

Type of Paper: Technical Note
Title: Nanomaterials in Lubricants: Myths and Facts
Authors: Boris Zhmud and Bogdan Pasalskiy
Affiliations: Applied Nano Surfaces, Knivstagatan 12, Uppsala 75323, Sweden
Abstract: The present paper overviews the use of various classes of nanomaterials in lubricant formulations. The following classes of nanomaterials are considered: fullerenes, nanodiamonds, fumed silica, clays, ultradispersed boric acid and PTFE. Current advances in using nanomaterials in engine oils, industrial lubricants and greases are discussed. Results of numerous studies combined with formulation experience of the authors conclusively suggest that nanomaterials, indeed, have potential for enhancing certain lubricant properties, yet there is a long way to go before balanced formulations are developed.

Type of Paper: Research Paper
Title: Tribological Performance of Non-doped and Ti-doped DLC Coatings Lubricated by Low-SAPS Additive Formulations and the Link with Tribochemistry Effects
Authors: Hongyuan Zhao, Ardian Morina, Anne Neville, Jiancun Rao, Jeff de Hosson and Frederic Meunier
Affiliations: School of Mechanical Engineering, University of Leeds, Leeds, UK; 2. Department of Applied Physics, University of Groningen, Groningen, Netherlands; 3. Sulzer SOREVI SAS, Limoges Cedex, France.
Abstract: Diamond-like-carbon (DLC) coatings have been one of the most popular topics for automotive powertrain material research in the last decade. Many fundamental research papers have been published in previous years, for which most of the tests were performed in vacuum, with a controlled gas supply, water, base oil or single-additive oil formulations. This current study has taken a close look at how DLC coatings perform when lubricated by some new engine oil formulations. Ti-doped DLC was tested together with non-doped pure hydrogenated DLC to investigate the effects of the metallic doping elements on tribological performance and tribofilm composition. Current and new low Sulphated Ashes, Phosphorus, and Sulphur (SAPS) diesel engine oil technology formulations were used as the lubricants in the tests. Friction and wear results were obtained which indicated the dependence on the oil type. Post-test surface analysis techniques, such as XPS and TOF-SIMS were applied to study the tribofilm formation on DLC surfaces. Some functional groups, such as PO2-and OH-related groups were found to have high intensities in the wear tracks and were linked with good tribological performance. Ti-DLC showed an increased reaction rate with Ca- and P-containing additives compared with non-doped DLC. Some friction and wear reduction mechanisms were proposed to be related with the tribochemsitry effects in this study.

Type of Paper: Technical Note
Title: Nanomaterials in Lubricants: Myths and Facts
Authors: Boris Zhmud and Bogdan Pasalskiy
Affiliations: Applied Nano Surfaces, Knivstagatan 12, Uppsala 75323, Sweden
Abstract: The present paper overviews the use of various classes of nanomaterials in lubricant formulations. The following classes of nanomaterials are considered: fullerenes, nanodiamonds, fumed silica, clays, ultradispersed boric acid and PTFE. Current advances in using nanomaterials in engine oils, industrial lubricants and greases are discussed. Results of numerous studies combined with formulation experience of the authors conclusively suggest that nanomaterials, indeed, have potential for enhancing certain lubricant properties, yet there is a long way to go before balanced formulations are developed.

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