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Isocyanate-Functionalized Chitin and Chitosan as Gelling Agents of Castor Oil
Department of Chemical Engineering, Physical Chemistry and Organic Chemistry, University of Huelva, Campus El Carmen, Campus ceiA3, 21071 Huelva, Spain
CIQSO—Center for Research in Sustainable Chemistry, University of Huelva, 21071 Huelva, Spain
PRO2TEC—Chemical Process and Product Technology Research Center, University of Huelva, 21071 Huelva, Spain
* Author to whom correspondence should be addressed.
Received: 19 March 2013; in revised form: 29 May 2013 / Accepted: 31 May 2013 / Published: 3 June 2013
Abstract: The main objective of this work was the incorporation of reactive isocyanate groups into chitin and chitosan in order to effectively use the products as reactive thickening agents in castor oil. The resulting gel-like dispersions could be potentially used as biodegradable lubricating greases. Three different NCO–functionalized polymers were obtained: two of them by promoting the reaction of chitosan with 1,6-hexamethylene diisocyanate (HMDI), and the other by using chitin instead of chitosan. These polymers were characterized through 1H-NMR, FTIR and thermogravimetric analysis (TGA). Thermal and rheological behaviours of the oleogels prepared by dispersing these polymers in castor oil were studied by means of TGA and small-amplitude oscillatory shear (SAOS) measurements. The evolution and values of the linear viscoelasticity functions with frequency for –NCO–functionalized chitosan- and chitin-based oleogels are quite similar to those found for standard lubricating greases. In relation to long-term stability of these oleogels, no phase separation was observed and the values of viscoelastic functions increase significantly during the first seven days of ageing, and then remain almost constant. TGA analysis showed that the degradation temperature of the resulting oleogels is higher than that found for traditional lubricating greases.
Keywords: chitin; chitosan; castor oil; isocyanate; lubricating grease; rheology
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Gallego, R.; Arteaga, J.F.; Valencia, C.; Franco, J.M. Isocyanate-Functionalized Chitin and Chitosan as Gelling Agents of Castor Oil. Molecules 2013, 18, 6532-6549.
Gallego R, Arteaga JF, Valencia C, Franco JM. Isocyanate-Functionalized Chitin and Chitosan as Gelling Agents of Castor Oil. Molecules. 2013; 18(6):6532-6549.
Gallego, Rocío; Arteaga, Jesús F.; Valencia, Concepción; Franco, José M. 2013. "Isocyanate-Functionalized Chitin and Chitosan as Gelling Agents of Castor Oil." Molecules 18, no. 6: 6532-6549.