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Polymers 2014, 6(7), 1929-1947; doi:10.3390/polym6071929

Influence of Functionalization Degree on the Rheological Properties of Isocyanate-Functionalized Chitin- and Chitosan-Based Chemical Oleogels for Lubricant Applications

1
Department of Chemical Engineering, Physical Chemistry and Organic Chemistry, University of Huelva, Campus El Carmen, Campus ceiA3, 21071 Huelva, Spain
2
CIQSO—Center for Research in Sustainable Chemistry, University of Huelva, 21071 Huelva, Spain
3
Pro2TecS—Chemical Product and Process Technology Center, University of Huelva, 21071 Huelva, Spain
*
Author to whom correspondence should be addressed.
Received: 30 May 2014 / Revised: 27 June 2014 / Accepted: 28 June 2014 / Published: 8 July 2014
(This article belongs to the Special Issue Chitin and Chitosans)
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Abstract

This work deals with the influence of functionalization degree on the thermogravimetric and rheological behaviour of NCO-functionalized chitosan- and chitin-based oleogels. Chitosan and chitin were functionalized using different proportions of 1,6-hexamethylene diisocyanate (HMDI) and subsequently dispersed in castor oil to promote the chemical reaction between the –NCO group of the modified biopolymer and the –OH group located in the ricinoleic fatty acid chain of castor oil, thus resulting in different oleogels with specific thermogravimetric and rheological characteristics. Biopolymers and oleogels were characterized through Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Small-amplitude oscillatory shear (SAOS) measurements were performed on the oleogels. Oleogels presented suitable thermal resistance, despite the fact that the inclusion of HMDI moieties in the polymer structure led to a reduction in the onset temperature of thermal degradation. The insertion of low amounts of HMDI in both chitin and chitosan produces a drastic reduction in the values of oleogel viscoelastic functions but, above a critical threshold, they increase with the functionalization degree so that isocyanate functionalization results in a chemical tool to modulate oleogel rheological response. Several NCO-functionalized chitosan- and chitin-based oleogel formulations present suitable thermal resistance and rheological characteristics to be proposed as bio-based alternatives to traditional lubricating greases. View Full-Text
Keywords: biopolymer; isocyanate-functionalized chitin and chitosan; oleogel; lubricating greases; rheology biopolymer; isocyanate-functionalized chitin and chitosan; oleogel; lubricating greases; rheology
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This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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MDPI and ACS Style

Gallego, R.; González, M.; Arteaga, J.F.; Valencia, C.; Franco, J.M. Influence of Functionalization Degree on the Rheological Properties of Isocyanate-Functionalized Chitin- and Chitosan-Based Chemical Oleogels for Lubricant Applications. Polymers 2014, 6, 1929-1947.

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