Zhou, Lili2011-05-022011-05-022010-12https://hdl.handle.net/11299/103595University of Minnesota M.S. thesis. December 2010. Major: Natural resources science & management. Advisor: Dr. William Tai Yin Tze. 1 computer file (PDF); ix, 63 pages.The overall goal of this project was to investigate all-cellulose composites prepared in a “green” solvent – ionic liquid. The approach was to partially dissolve cellulose and subsequently convert it into a matrix domain embedding the reinforcement domain – the undissolved cellulose. Microcrystalline cellulose (MCC) was partially dissolved in 1-N-Butyl-3-methylimidazolium chloride (BMIMCl) ionic liquid. The dissolved portion of cellulose was precipitated by adding water, and the gels obtained were washed, dried, and pressed into films. The all-cellulose composite films were structurally characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM), while their properties were determined using tensile tests and dynamic vapor sorption (DVS) studies. XRD results verified that the crystallinity index and weight fraction of cellulose I in the composites can be controlled by controlling the soaking time and cellulose concentrations. The tensile test data revealed that the all-cellulose composite produced in this study had mean elastic moduli and strength of up to 4.4 GPa and 49 MPa, respectively, which are in the range of a randomly oriented biofiber-reinforced polymer composites. The tensile properties increased as a response to the composite density, which was found to increase as more cellulose II matrix (from increased dissolution) was present to presumably better fill the voids. This presumption was supported by SEM images of cryo-fractured surfaces. The sorption isotherms obtained from DVS studies showed a non-sigmoidal behavior at low relative humidity levels (<44%), while the equilibrium moisture content values at higher humidity levels closely correlated to the cellulose I crystallinity index of the composites. Overall, this study verified that dissolution of cellulose in ionic liquid can be controlled to control the properties of all-cellulose composites.en-USNatural resources science & managementThesis or Dissertation