Studies On Construction、Structure And Properties Of A New Class Of Cellulose Bioplastic

Nowadays, the plastics are widely used in various area due to their lightweight, waterproof, durable, low-cost and so on. However, most of the plastics are fabricated from synthetic polymers derived from petrochemicals, which are exhaustible and non-biodegradable material and have caused serious environmental problems. Bioplastics are produced from renewable resources rather than fossil-fuel plastics which are derived from petroleum, and are biodegradable plastics. Cellulose is the most abundant natural polymer on earth. Cellulosic compounds are available for extrusion, injection molding, blow molding, and rotational molding, but it was hard to envision that cellulose can be directly used to fabricate a material like synthetic polymer as thermoplastic or thermosetting plastics because the rigid molecules of cellulose are closely packed and not melt processing.This work focused on fabricating plastic from cellulose rather than its cellulose derivatives. First, cellulose was dissolved in NaOH/urea or LiOH/urea aqueous solution precooled to-12℃and then cellulose hydrogels were prepared in non-solvent. On the basis of the removability of cellulose molecules beam in hydrogel state, cellulose bioplastic are constructed by hot-pressing. At the same time, functioned material are fabricated by introducing the inorganic or organic matter into cellulose plastic through non covalent force. The structure and properties of cellulose plastics were characterized with scanning electron microscopy (SEM),13C-Solid NMR, wide angle X-ray diffraction (XRD), thermogravimetry analysis (TGA), dynamic mechanical thermal analysis (DMTA) and thermomechanical analysis (TMA) and so on.The innovation of this work was listed as follows.(1) On the basis of the removability of cellulose molecules beam in hydrogel state and breaking through the traditional methold of heating and melting process, a new class of cellulose bioplastic with high strength, good thermal stability and low coefficient of thermal expansion was constructed from cellulose hydrogel by changing aggregated structure via the hot-pressing process.(2)Based on the hydrogen-bond interaction between cellulose and fluorescent molecules, fluorescent cellulose bioplastics were fabricated.(3) On the basis of affinity between clay and cellulose, clay/cellulose bioplastics were prepared by dispersing caly into cellulose solution.(4) TiO2/cellulose hybrid matrials are fabricated by in-suit synthesis in cellulose matrix and a phase transformation of TiO2from amorphous to anatase occurred at mild temperature.(5) Ag3PO4/cellulose nanocomposite hydrogels have been successfully synthesized by two steps using cellulose itself reducing and H2O2oxidation capacity and introduces its photocatalytic properties under visible light.(6) By controlling the moisture content of zinc nitrate solution and decomposition speed of OH-, ZnO/cellulose composites with different ZnO crystal shape are fabricated.The primary contents and conclusion of this work can be derived into six parts.A new class of bioplastics was successfully fabricated from the cellulose hydrogels prepared in the alkali hydroxide/urea aqueous solution by changing aggregated structure via hot-pressing process. The thermocompression of cellulose hydrogel reduced a radial orientation of cellulose molecular beam in the planar direction of the plate, and an increase of amorphous zones in the vertical direction. The bioplastics had the uniform parallel orientation structure, leading to the good optical transmittance. Moreover, the cellulose bioplastic exhibited much higher tensile strength, the flexural strength and thermal stability as well as lower coefficient of thermal expansion than the common plastics and the regenerated cellulose films. The hot-pressing contributed to the transition of the aggregated structure in the cellulose hydrogel state, leading to the orderly stretching and orientation of the cellulose chains in the bioplastics. The whole life cycle assessment indicated that the cellulose bioplastic was an environmentally friendly material. This new avenue to construct bioplastic from the cellulose pulp is important for a sustainable world.Based on the strong hydrogen bond between cellulose hydroxyl and the polar groups of fluorescent molecules, fluorescent cellulose bioplastics are fabricated. RhB/cellulose bioplastic and fluorescein/cellulose bioplastic are prepared by hot-pressing cellulose hydrogel containing fluorescent molecules. At the same time, a radial orientation of cellulose molecular beam in the planar direction of the plate are induced by hot-pressing. Due to the affinity of the hydroxyl groups and micro nano pore structure, cellulose hydrogel can be ready to hold and fix dye molecules, leading to fluorescent plastics. Moreover, the dye molecule has no chemical change during the hot pressing process, and the fabrication of bioplastic was a physical process. The fluorescent plastic with thermal stability, excellent mechanical properties and photoluminescence properties have a potential applications in optical materials and security devices.Clay/cellulose bioplastic were constructed by uniformly dispersing clay in cellulose matrix. The result of TEM, SEM and FT-IR showed clay were well-fixed in cellulose plastic as a result of the interfacial hydrogen bond interaction between clay and cellulose. With the increase of clay content, the tensile strength of composite plastic increased gradually, and more closely structure between the clay layers were shown. This bioplastics with smooth surface, good mechanical properties and thermal stability, have prospect application in the field of air resistance, flame retardant and packaging material etc.TiO2/cellulose aerogels were fabricated successfully by in-suit synthesis of TiO2nanoparticles in the regenerated cellulose matrix, and drying with supercritical CO2. The TiO2nanoparticles with small size were well dispersed and embedded in the cellulose matrix. A phase transformation of TiO2from amorphous to anatase occurred via in-suit synthesis at mild temperature. By increasing of the treating times immersed into a tetrabutyl titanate the TiO2content in the TiO2/cellulose aerogel could achieve up to60wt%. The TiO2/cellulose composites were opal, as a result of the abundant TiO2, and exhibited good toughness and excellent strength. The TiO2/cellulose aerogels displayed highly effective photocatalytic activities for the degradation of methyl orange (MO) under ultraviolet light irradiate. These characters of the TiO2composites would be very important for the wide application.Ag3PO4/cellulose nanocomposite hydrogels have been synthesized successfully by two steps using cellulose itself reducing and H2O2oxidation capacity. The Ag3PO4nanoparticles at different AgNO3concentration were dispersed uniformly in the regenerated cellulose hydrogels and their average diameter was in the range from3.1±2.7to11±4.5nm and slightly increased with an increase of Ag3PO4concentration. The AgsPO4/cellulose nanocomposite hydrogels had good degradation efficiency of photocatalytic degradation on Rh B, and Ag3PO4nanoparticle size was smaller and the degradation efficiency was higher. The Ag3PO4/cellulose nanocomposite hydrogels exhibited excellent mechanical properties and moderate thermal stability. This material has potential application in field of visible light photocatalytic, water treatment and solar energy conversion.Based on tiny amounts of water in Zn(NO3)26H2O ethanol solution can promote hydrated zinc ions generated, and epoxy propane can be used as proton capturing agent and lead to hydrated zinc ion hydrolyzed to Zn(OH)(H2O)52+. With the aid of the micro-nano porous structure of the cellulose gel and using epoxy propane steam induced zinc nitrate sol-gel transition, ZnO grain successfully were prepared in the cellulose matrix. The role of hexamethylenetetramine in ZnO array growth is to keep the crystallization of ZnO under thermodynamic control by the slow release of OH" ions. ZnO seeds were grown in Zinc nitrate hexahydrate/hexamethylenetetramine solution or ethanol solution. When the ZnO seeds were grown in water phase, hexamethylene tetramine in a normal speed providing OH-ions can keep the growth of ZnO seed along the (0001) direction and rod-like crystal were obtained. However, when ZnO seeds were grown in water phase, hexamethylene tetramine in a slow speed providing OH" ions can induce the aggregation of ZnO nanorods and the cap-like of ZnO were grown. Thus, by controlling the water content and the rate of decomposition of OH-ions, ZnO crystal with different shapes were fabricated on the cellulose substrate. This composite material with good mechanical, thermal properties, UV absorption properties and excellent photocatalytic degradation Cr6+feature has a potential applications in the field of wastewater treatment.The main work of this thesis is a new class bioplastic and composites are constructed on the basis of the alkali/urea aqueous to dissolve cellulose at low temperature to form a transparent solution, and elucidate the relationship between the structure and properties of cellulose plastic and composite. Thus a new class of cellulose bioplastic, fluorescent bioplastic and various inorganic/organic hybrid materials with different functions were fabricated. Moreover, they are environment-friendly biodegradable plastics. Therefore, this dissertation has obvious innovation, scientific merit and potential applications.