Article pubs.acs.org/IECR
Foamlike Xanthan Gum/Clay Aerogel Composites and Tailoring Properties by Blending with Agar Liang Wang,† David A. Schiraldi,‡ and Miguel Sánchez-Soto*,† †
Centre Catalá del Plàstic, Universitat Politécnica de Catalunya, Colom 114, 08222 Terrassa, Spain Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106-7202 United States
‡
ABSTRACT: Foamlike aerogel composites based on renewable xanthan gum (XG) and sodium montmorillonite clay (Na+MMT) have been prepared using an environmentally friendly freeze-drying process. Additionally, the biobased polysaccharide agar was used to improve the properties of XG/clay aerogels. Fourier transform infrared spectroscopy showed molecular interactions between biopolymers and clay in the aerogel composites. A wide range of microstructures and mechanical properties were obtained with a minimal variation in the density by changing the blended ratio of xanthan gum and agar, with particular emphasis on the addition of 2.5% agar to XG/clay aerogels, which significantly enhanced the mechanical properties. Thermogravimetric analysis revealed that clay improved the thermal stability of aerogels; however, the thermal stability of blends of xanthan gum and agar worsened. Flammability was analyzed through cone calorimeter, which suggested xanthan gum/clay aerogels possessed lower flammability than other typical foams. Clay served as a heat and mass transport, which significantly improved the flame retardancy of the base aerogels. chains consisting of β-D-(1 → 2)-mannose attached to alternate glucose units in the main chain.15,16 Agar consists of a mixture of agarose and agaropectin, in which the former is the predominant component consisting of a linear polymer made up of D-galactose and 3,6-anhydro-Lgalactopyranose, and the latter is a heterogeneous mixture of smaller molecules;17 it has been used extensively as a gelling agent in the food industry because of its excellent ability to form hard gels at low concentrations. Synergic effects between different polysaccharides have been reported, such as the improvement in viscosity in agar/locust bean gum (LBG) mixtures.18 Cases of tailored strength and texture of agar/LBG gels have also been studied based on changing the ratio of agar and LBG.19 Xanthan gum solutions at low temperature (
