Novel gelling systems of kappa-, iota- and lambda-carrageenans and their composite gels with cellulose using ionic liquid.

Gels of three types of carrageenans (kappa-, iota- and lambda-), as well as their composite gels with cellulose, were prepared using an ionic liquid, 1-butyl-3-methylimidazolium chloride (BMIMCl), by a heating-cooling process. kappa-Carrageenan gave the formation of hard gel while the other two carrageenans gave the formation of softer gels with BMIMCl. The gels were characterized by X-ray diffraction (XRD), thermal analysis (TGA and DSC), scanning electron microscope (SEM) and compressive testing. The results indicated that, among the three types of carrageenans, kappa- and iota-carrageenans gave better miscible gels with BMIMCl, followed by lambda-carrageenan. On the other hand, lambda-carrageenan gave a better miscible composite gel with cellulose and BMIMCl, followed by iota- and kappa-carrageenans. The stress-strain curves indicated that the mechanical properties of the above gel systems on the compressive mode were much better than those of the hydrogels of kappa- and iota-carrageenans as well as the cellulose gel with BMIMCl.