Study On Regenerated Cellulose Composite With Fe₃O₄, Carbon Nanotubes And Graphene

With the decreasing amount of the reserved petroleum and increasing amount of pollution caused by the oil-based products, it is urgent and promising to develop bio-based polymer as supplement for the non-degraded synthetic polymers. Cellulose, the most abundant natural polymer in nature, is renewable, biodegradable, and biocompatible. Therefore, increasing attention has been paid to cellulose as an inexhaustible source of raw material to replace petrochemically derived compounds in many applications. Nowadays, the regenerated cellulose products such as membranes and fibers have been widely developed over a series of industry applications.The effect of Fe3O4, carbon nanotubes and graphene on regenerated cellulose composite has been investigated in this thesis. The present work includes four parts as follows:(1) The cellulose was dissolved in 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), and the solution was casted and coagulated in a water bath under appropriate conditions. Then magnetic composite films were fabricated by introducing in-situ synthesized Fe3O4 nanoparticles into the wet cellulose films, in which regenerated cellulose (RC) film was used as a matrix and mixture solutions of Fe3+/Fe2+ as precursors. The structure and morphology of the composite films were studied by Scanning electron microscopy and X-ray diffraction. The results indicate that the spherical magnetic Fe3O4 nanoparticles were dispersed uniformly and immobilized in the matrix, and the structure of Fe3O4 are perfect. FT-IR results demonstrate that there are good interactions between cellulose and Fe3O4 in the films, leading to the formation and stabilization of the novel magnetic materials. The thermogravimetric analysis reveals that with an increasing concentration of precursors from 0.01 to 0.5, the content of Fe3O4 nanoparticles in the dried composites films increases from 6.8% to 28.3%. The cellulose composite films show a higher mechanical strength than that of RC films. Therefore, a simple and effective way is provided to prepare the regenerated-cellulose/Fe3O4 composite films that might be used for the production of cellulose-based films.(2) Carbon nanotubes (CNTs) exhibit novel structure-related physical and chemical properties due to their unique one-dimensional tubular structure, and show significant potential applications for electronic devices, composite materials, and catalysts. The structure and mechanical properties of the composite films were investigated by X-ray diffraction, scanning electron microscopy, and mechanical testing, respectively. The results reveal that a significant enhancement of mechanical properties has been achieved, that is,184% improvement of tensile strength and 54% increase of tensile modulus with 5wt.% MWCNTs loading. The simultaneous improvement of strength and toughness could be attributed to the homogeneous dispersion of CNTs in the RC matrix. The comparison between the experimental results and the Halpin-Tsai theoretical prediction indicates that MWCNTs might be randomly distributed in the RC matrix. Meanwhile, it is interesting to note that all the composites films are transparent. The overall mechanical performance of the composites is suitable for further use in some fields which need materials with higher mechanical properties.(3) Graphene has attracted attention because of its remarkable physical properties and chemical functionalization capabilities. We present the preparation of graphene/RC composites through solution blending. The structure and mechanical properties of the composite films were investigated by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and mechanical testing, respectively. A significant enhancement of mechanical properties is achieved, with 137% improvement of tensile strength and 95% increase of tensile modulus with 5wt.% graphene loading. The simultaneous improvement of strength and toughness is due to the uniform dispersion of graphene and alignment of graphene nanosheets in the RC matrix, and the strong interfacial interactions between graphene and RC, as well as the higher crystallinity of the composites compared to the pure RC film.(4) Despite great development with graphene-based materials, the progress of strong and cost-efficient multifunctional graphene-filled polymer composites has few to be made. A key challenge in the preparation of nanoplatelet-filled polymer composites is the ability to realize the nanometer-level dispersion and the planar orientation of nanosheets in polymer matrices. In this report, multilayer films were successfully fabricated by layer-by-layer assembly of regenerated cellulose and exfoliated graphene oxide, in which exfoliated graphene oxide nanosheets were used as the building blocks. Typical field emission scanning electron microscope images demonstrate an ordered arrangement of layers. The thickness of 50 layer film is about 20μm and the film exhibits a high degree of smoothness. This may be attributed to the well-defined layered structure with high degree of planar orientation and nanolevel assemblies of graphene oxide nanosheets in the polymer matrices. The electrical conductivity of the multilayer films shows a remarkable increase with increasing number of layers in the films.