Preparation and characterization of carbon nanotubes/chitosan composite foam with enhanced elastic property

Carbon nanotubes/chitosan (CNTs/CHI) composite foams with ordered lamellar structure were prepared by unidirectionally freezing a dispersion of CNTs in chitosan aqueous solution and subsequent freeze drying. The structure and thermal stability of the composite foams have been characterized by wide-angle X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetry analysis. And their elastic behaviors were investigated by cyclic compression tests. The produced CNTs/CHI composite foams have better recoverability and improved elastic properties compared with the pure chitosan foams. Freezing rate, fraction of CNTs and density are the important factors affecting on the micro morphology, elasticity and mechanical strength of CNTs/CHI composite foams. Due to less ice dendrites and thicker lamellas being formed under low freezing rate, the CNTs/CHI composite foams prepared under low freezing rate (6 mm min(-1)) possesses better mechanical properties than those prepared under high freezing rate (10 cm min(-1)). With the increasing CNTs fraction, the recovery ability of CNTs/CHI composite increases and achieves the maximum at a critical point, and then decreases dramatically due to the inadequate chitosan matrix and aggregation of CNTs. The critical point herein appears at the CNTs fraction ≥ 0.5 and ≥ 0.3, respectively, for the samples with density of 0.02 and 0.01 g cm(-3). The CNTs/CHI composite foams with high density (0.02 g cm(-3)) possess better elasticity and mechanical strength than the ones with low density (0.01 g cm(-3)).