The effect of ethoxylated esters on the lubricating properties of their aqueous solutions

Abstract

In many applications strict ecological criteria are crucial. Water is often used in these cases as a lubricant base. Its disadvantageous properties, in particular lubricity, can be modified by introduction of additives. Ethoxylated methyl esters of fatty acids from rapeseed oil were chosen for that purpose. In order to verify tribological properties of aqueous solutions of these compounds, anti-seizure properties under linearly increasing load, friction and wear under 2 kN (four-ball machine) were assessed. Not only radical change of tribological properties as compared to water was observed, but also the results are comparable to the ones obtained for mineral oils, which contained typical, commercial additives. Significant changes in scuffing load (P t ), seizure load (P oz ), limiting pressure of seizure (p oz ) were recorded even at 0.1% wt concentration of the additive. At optimal concentration P t , P oz , p oz , increased even almost 6-, 2-and 3-fold (respectively). The quantities measured increased with ethoxylation degree. Also at constant load, friction (6-fold) and wear (almost 2-fold) were reduced. In this case, however, no influence of concentration and ethoxylation degree on the quantities measured, was observed.The tribological properties can be discussed in terms of results of physical-chemical tests. Ethoxylates are surface active compounds. Within the range of concentrations analyzed, they form micelles in a bulk phase and liquid-crystalline structures in a surface phase. High surface activity of these additives and creation of specific structures in solutions were proved by measuring surface tension, wetting angle and mesophases observation in polarized light. On the basis of the results of the physical-chemical and tribological tests one can conjecture that profitable tribological properties of the lubricating compositions are the result of strong affinity to the surface and their ability to form ordered structures. One can expect that over the cooperating surfaces a deposit is formed. Presence of the deposit increases real contact area and prevents seizure. This hypothesis gives a simple explanation of the unexpected improvement of anti-seizure properties, which accompanies the increase of ethoxylation degree. Ethoxylates with higher number of ethylene oxide attached, reveal smaller surface activity and better solubility in water. On the other hand, they can be characterized by higher dehydratation temperature. This means that at higher temperatures they reveal surface activity. That is why, during seizure tests, at high temperature, under high loads the esters of higher ethoxylation degree protect friction couples against seizure much more efficiently.

The Effect of Concentration on Lubricating Properties of Aqueous Solutions of Sodium Lauryl Sulfate and Ethoxylated Sodium Lauryl Sulfate

“…The results of studies on surfactants as lubricity modifiers for both oil and water bases have been presented in literature [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. The interpretation of the results obtained is often based on simplified physicochemical models.…”

Lubricating Properties of Organic Phosphate Ester Aqueous Solutions

“…Lei et al [6] added the fullerene-styrene sulfonic acid copolymer into water to improve its anti-pressure properties. Sulek et al [7] have investigated the effect of ethoxylated esters on the lubricating properties of aqueous solutions and discussed the tribological properties in terms of results of physicochemical tests.…”

“…Organic phosphate ester (DPZ): a FTIR spectrometer and b chemical formula (R-alkyl chain: C7-C20; n:[5][6][7][8][9][10][11][12][13][14][15] …”

Ecological Cutting Fluids

“…Just like solutions of other surfactants aqueous sarcosinate solutions they can be used in lubrication technology [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. In order to confirm this thesis, we planned to carry out stand and operational tests for working fluids (SWF) composed of aqueous solution of sodium lauroyl sarcosinate (2%), antifoam additive (0.05%) and biocide (0.1%).…”

“…The analysis of aqueous solutions of surfactants indicates that they have not been included in any of the presented types of working fluids. In view of the possible application of aqueous surfactant solutions as lubricants, which was documented in numerous publications [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ], it was proposed to create two new groups termed surfactant working fluids (SWFs) and surfactant lubricants (SLs). The aims of the introduction of this new classification (SWFs and SLs) are to avoid ambiguity in the description and to create a basis for a targeted development of this type of working and hydraulic fluids and, in the long term, a different group of lubricants.…”