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Adsorption of fatty acids from alkane solution studied with quartz crystal microbalance
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
YKI, Institute for Surface Chemistry, Stockholm, Sweden.
YKI, Institute for Surface Chemistry, Stockholm, Sweden.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
2006 (English)In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 22, no 1, 15-20 p.Article in journal (Refereed) Published
Abstract [en]

This paper describes the adsorption of the unsaturated fatty acids, oleic-, linoleic-, and linolenic acid onto steel coated quartz crystal surfaces from 2,2,4,4,6,8,8-heptamethylnonane as monitored by the quartz crystal microbalance (QCM) technique. It is shown that addition of fatty acid to the oil results in changes in bulk density and viscosity and that these changes must be considered before the sensed mass can be evaluated. The change in viscosity of the solution is larger for oleic acid than for linoleic acid and linolenic acid, which results in a larger correction for oleic acid with respect to bulk effects. After considering the effects due to changes in bulk properties, the influence of the viscoelastic properties of the adsorbed layer on the sensed mass was evaluated. The correction for the viscoelastic properties of the adsorbed layer was found to be very small for the systems studied. The sensed mass, at 1.1 weight percent, ranged from 0.5 mg/m(2) for oleic acid to 5 mg/m(2) for linolenic acid.

Place, publisher, year, edition, pages
2006. Vol. 22, no 1, 15-20 p.
Keyword [en]
fatty acid, adsorption, quartz crystal microbalance (QCM), alkane, steel, solid-surfaces, qcm-d, frequency, liquid, films, resonator, contact, surfactants, gold
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-15845DOI: 10.1007/s11249-005-9000-9ISI: 000239002400002Scopus ID: 2-s2.0-33745806904OAI: oai:DiVA.org:kth-15845DiVA: diva2:333887
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Unsaturated Fatty Acids in Alkane Solution: Adsorption and Tribological Properties
Open this publication in new window or tab >>Unsaturated Fatty Acids in Alkane Solution: Adsorption and Tribological Properties
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Fatty acids and blends of fatty acids are used as friction modifiers and anti-wear additives in diesel fuels. A large part of some fatty acid blends are unsaturated fatty acids. Even though fatty acids have been thoroughly investigated, the adsorption and tribological behaviour of unsaturated fatty acids are no fully understood. The aim of this thesis was to investigate the influence of fatty acid unsaturation on the adsorption from alkane solution and the tribological properties, such as friction and wear scar characterization, of such systems.

To increase the fundamental understanding of the influence of the degree of fatty acid unsaturation the three fatty acids, oleic, linoleic and linolenic acid, have been studied. In boundary lubrication the amount of material and how well the material is bound to the surface can affect the friction and wear of the system. Thus, as a first step the adsorption of fatty acids onto steel surfaces was investigated with the quartz crystal microbalance (QCM). This technique is straight forward to used and is ideal for these samples that are difficult to investigate with optical techniques due to small differences in refractive index between the alkane solvent and fatty acid. To determine the chemical binding to steel surfaces static secondary ion mass spectroscopy (SIMS) has been used.

Next, the influence of fatty acid unsaturation on the friction and wear was determined. Two different studies were made, one on a molecular level with the tribological surfaces forces apparatus (T-SFA) and the other one with a technique used for determining friction and wear of diesel fuel additives. The T-SFA technique provides data from which the packing of the fatty acids at mica surfaces can be estimated as well as how the friction is altered due to the packing. For determining the friction and wear of steel surfaces the high frequency reciprocating rig (HFRR) and pin on disc apparatus (POD) were used. The HFRR is a standardized technique, where, if the settings specified in the ISO12156 protocol are used, a diesel fuel additive must provide an average wear scar radius less than 0.230 mm to pass. The wear scars received from the two techniques were further analysed with Raman spectroscopy and also a visual rating of the wear scars was performed.

As the project progressed, there was an increasing interest in the influence of water on the adsorption and lubricating properties of the fatty acids. Moisture uptake of the fatty acids was therefore determined gravimetrically as well as with nuclear magnetic resonance spectroscopy (NMR). The adsorption of the moist fatty acids onto steel surfaces was then investigated with QCM and static SIMS, while HFRR and POD were used for investigate the friction and wear.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. iv, 44 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:5
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-4616 (URN)978-91-7178-854-2 (ISBN)
Public defence
2008-02-15, F3, KTH, Lindstedtsvägen 26, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100824Available from: 2008-01-28 Created: 2008-01-28 Last updated: 2010-08-24Bibliographically approved

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