Acetylation Of Cellulose Nanocrystals And Study On Modified Polyurethane Materials

It is the new researching topic of nanocomposite materials that biomass nano-materials are used as fillers to modify polymeric matrix. The materials are composed of polymeric matrix and nano-fillers, so which show some nano-structure effect. In contrast to traditional particles, nano-particles have volume effect, macroscopic quantum tunneling effect, surface and interface effect, express special electrical, optical, magnetic and chemical properties. Due to so many excellent properties of nano-particles can we open a new way of using them to prepare lots kinds of multifunctional and high-performance composite materials.This work chose a natural polymer material with nanofabrication——cellulose nanocrystal (CN), which should show preferable compatibility and dispersion in organic solvent through surface acetylation. Meanwhile, toluene diisocyanate (TDI), castor oil and1,4-butanedione (1,4-BDO) were adopted as the main raw material for the preparation of polyurethane. Acetylated cellulose nanocrystalline (ACN) was blended with castor oil-based polyurethane, the nanocomposites with a higher loading level of biomass was gained. The characterization and structure of nanocomposites were investigated by a series of testing about mechanical properties and thermodynamic performance.The main researching results of this thesis are as follows:(1) acetylated cellulose nanocrystals were prepared based on the reaction between acetic anhydride and the rich hydroxyl groups on the surface of cellulose nanocrystals. As a result, the crystalline structure and morphology of ACN have not been destroyed basically, however, the dispersity and stability of them in the organic solvent have been remarkably improved;(2) high-loading natural nano-fillers reinforced castor-oil-based polyurethane composite materials with high performance were prepared using cast film-forming method. The loading level of nano-fillers has reached to amazing25%, the strength and modulus became more and more high as the loading increasing, and they increased to10.41MPa and42.61MPa, respectively. Meanwhile, the elongation at break had remarkable improvement relative to pure polyurethane, which reached to the max value of444%when the loading was10%, was2time than pure polyurethane.Surface acetylation of cellulose nanocrystal successfully improved the compatibility and dispersion of cellulose nanocrystal in organic solvent, without destroying its original morphology and crystal structure, and then acetylated cellulose nanocrystalline was introduced in castor oil-based polyurethane to prepare a nanocomposite with higher loading level of biomass and excellent mechanical properties. The work may provide a reference for the development of environmentally friendly materials.