Fabrication, Structures And Properties Of Nanocellulose Reinforced Polymer Film/Foam Composites

With the increasing focus on sustainable development, utilization of bio-based materials became more and more important. The bio-based materials are supported with nanocellulose. Because nanocellulose has prospective properties such as high Young’s modulus and very low coefficient of thermal expansion, they are expected to be utilized as a filler of next generation nanocomposites. The present dissertation will focus on the preparation, characterization, and application of nanocellulose reinforced polymer nanocomposites. Wood nanocellulose were produced from bio-based materials. Then, nanocellulose reinforced polymer nanocomposites were fabricated and characterized. The main results can be summarized as follows:(1) High aspect ratio nanocellulose was successfully fabricated from poplar wood using high-pressure homogenizer treatment combined with chemical pretreatments. The nanocellulose colloid has good stability. The width of single nanocellulose is～3 nm. Most of nanocellulose are self-aggregated into bundles. The nanocellulose and their bundle are entangled into web-like structures.(2) Nanocellulose is utilized as building blocks to prepare nanocellulose film via filtration combined with hot press method. The nanocellulose films is used as reinforcing fillers for the composite films. The thickness of the nanocellulose film can be controlled by varying the volume of nanocellulose colloids used for filtration. From the top view, the nanocellulose film is organized by entangled high aspect ratio nanocellulose and nanocellulose bundles. The cross-section of the nanocellulose film exhibits lamellar structure. As the film is organized by nanocellulose with high crystallinity, the film displays advantage mechanical properties, high thermal stability and thermo-mechanical properties.(3) Utilizing nanocellulose film as reinforced filler, the nanocellulose reinforced polymethylmethacrylate (PMMA) composite film was fabricated by filling the pores of the nanocellulose with PMMA. As the pores of the nanocellulose film were filled with transparent PMMA, and the nanocellulose is in the nanoscale without light scattering, the composite film displays high optically transparency. The introduction of nanocellulose apparently increases the mechanical properties, thermal stability, and thermal-mechanical properties of the composite foams.(4) Three kinds of nanocellulose with various cellulose contents were fabricated from wood, flax, and cotton, respectively. Then, nanocellulose reinforced polypyrrole composite form was fabricated by in situ polymerization of pyrrole monomer on the surfaces of nanocelluse. The structure, crystal structure, thermal stability, and electrochemical property of the composite foam were investigated. Further, the composite foams were pyrolyzed, resulting in nitrogen doping carbon foams. The structure and electrochemical property of the three kinds of carbon foams were compared.(5) Lignosulfonate was used as polymer matrix; it is derived from world abundant lignin. Composite foam was fabricated by utilized nanocellulose to reinforce lignosulfonate. The effect of nanocellulose contents on the macro and micro structures of the nanocellulose reinforced lignosulfonate composite foam was investigated. The reinforced ability of nanocellulose for the lignosulfonate was examined. The thermal stability and thermal insulation character of the composite foam was also researched. The composite foam was found to display high biocompatibility.