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. 2018 Jun 16;10(6):670.
doi: 10.3390/polym10060670.

Modification of Alkali Lignin with Poly(Ethylene Glycol) Diglycidyl Ether to Be Used as a Thickener in Bio-Lubricant Formulations

Esperanza Cortés-Triviño  1 , Concepción Valencia  2 , Miguel A Delgado  3 , José M Franco  4
Affiliations

Modification of Alkali Lignin with Poly(Ethylene Glycol) Diglycidyl Ether to Be Used as a Thickener in Bio-Lubricant Formulations

Esperanza Cortés-Triviño et al. Polymers (Basel). .

Abstract

Considerable efforts are currently being made by the academic community and industry, aiming to develop environmentally friendly lubricants with suitable technical features for their performance. In this context, lignin could be considered a promising candidate to be used as a bio-sourced thickening agent to formulate eco-friendly lubricating greases. In this work, alkali lignin (AL) was chemically modified with poly(ethylene glycol) diglycidyl ether (PEGDE). Afterwards, the epoxidized lignin was properly dispersed in castor oil (CO) in order to obtain an oleogel for lubricant applications. The epoxidized lignins were characterized by means of epoxy index determination, thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The epoxide-functionalized lignin-based oleogels were analyzed from both rheological and tribological points of view. It was found that the viscosity, consistency and viscoelastic functions of these oleogels clearly increased with the epoxy index of the epoxide-modified lignin compound. Thermo-rheological characterization of these oleogels revealed a slight thermal dependence of the viscoelastic moduli below 100 °C, but a significant softening above that critical temperature. In general, these oleogels showed low values of the friction coefficient under the mixed lubrication regime as compared to the neat castor oil.

Keywords: castor oil; epoxide-functionalized lignin; lubricating greases; rheology; tribology.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
FTIR spectra for the original alkali lignin and a selected epoxide-modified lignin (EAL4).
Figure 2
Figure 2
Loss weight (a) and decomposition-rates (b)curves during the thermal degradation for the original alkali lignin and epoxidized lignin samples.
Figure 3
Figure 3
Viscous flow curves at 25 °C for epoxidized lignin-based oleogels as a function of (a) lignin epoxy index (5 wt % EAL) and (b) lignin concentration (EAL1 sample).
Figure 4
Figure 4
Evolution of the storage (G′) and loss (G″) moduli with frequency for epoxidized lignin-based oleogel as a function of lignin epoxy index (5 wt % EAL). Star symbols correspond to the reference system prepared with non-epoxidized lignin and NaOH in the same proportion than sample EAL1. (G′, filled symbols; G″, empty symbols).
Figure 5
Figure 5
Evolution of the storage (G′) and loss (G″) moduli with frequency for epoxidized lignin-based oleogels prepared with sample EAL1 at different concentrations (G′, filled symbols; G″, empty symbols).
Figure 6
Figure 6
Evolution of GN0 with lignin epoxy index for EAL-based oleogels (5 and 10 wt % EAL) 24 h and 2 months after preparation.
Figure 7
Figure 7
Frequency dependence of the storage and loss moduli (a) and the loss tangent (b) for a selected epoxidized lignin-based oleogel (EAL1 at 5 wt %) as a function of temperature (G′, filled symbols; G″, empty symbols).
Figure 8
Figure 8
Evolution of GN0 with temperature for a selected oleogel (EAL1 at 5 wt %).
Figure 9
Figure 9
Friction coefficient versus rotational speed curves for epoxidized lignin-based oleogels as a function of (a) lignin epoxy index (5 wt % EAL) and (b) lignin concentration (EAL1 sample).
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References

    1. Luther R. Lubricants in the environment. In: Mang T., Dresel W., editors. Lubricants and Lubrication. Wiley-VCH; Weinheim, Germany: 2007. pp. 119–182.
    1. Flynn F.B. Screening for the potential of lubricant additives to biodegrade. NLGI Spokesm. 2000;63:8–13.
    1. Panchal T.M., Patel A., Chauhan D.D., Thomas M., Patel J.V. A methodological review on bio-lubricants from vegetable oil based resources. Renew. Sustain. Energy Rev. 2017;70:65–70. doi: 10.1016/j.rser.2016.11.105. - DOI
    1. Erhan S., Asadauskas S., Dunn R., Knothe G. Vegetable Oils for Environmentally Friendly Applications; Proceedings of the 48th Oilseed Conference, Competing in World Markets in the New Millennium; New Orleans, LA, USA. 28 Febrary 1999.
    1. Goodrum J.W., Geller D.P. Influence of fatty acid methyl esters from hydroxylated vegetable oils on diesel fuel lubricity. Bioresour. Technol. 2005;96:851–855. doi: 10.1016/j.biortech.2004.07.006. - DOI - PubMed

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