Study On Cellulose Nanofiber/Polyurethane Nanocomposite

In this research, cellulose nanofibers with high aspect ratio were isolated fromwood powder and newspapers respectively through chemical treatments andmechanical treatments, which were then composited with polyurethane to preparetransparent nanocomposites with high strength. The morphologies, chemicalconstitutes and diameter distributions of the cellulose nanofibers, and themechanical properties, optical properties and thermal stabilities of cellulosenanofiber/polyurethane nanocomposites were characterized and analysed.Conclusions based on this research were shown as following:(1) Cellulose nanofibers were extracted from wood powder and newspapersthrough chemical and mechanical treatments. Most of the newspaper cellulosenanofibers exhibited a diameter ranged from30to100nm and an aspect ratio of over1000. They were cross-linked together and formed a special three-dimensionalnetwork structure which was exactly the same as wood cellulose nanofibers.(2) Cellulose nanofiber/polyurethane nanocomposites were prepared byrespectively impregnating wood cellulose nanofiber sheet and newspaper cellulosenanofiber sheet into polyurethane resin, and the major chemical constitutes of bothwere polyurethane and cellulose. The mechical properties, optical properties andthermal stabilities of the resulted two nanocomposites were nearly the same.Compared with pure polyurethane film, the elastic modulus and tensile strength ofthe newspaper cellulose nanofiber/polyurethane were respectively increased1750%and209%, while the coefficient of thermal expansion (CTE) was decreased about90%.(3) The morphologies, chemical constitutes of the cellulose nanofibers and themechanical properties, optical properties and thermal stabilities of thenanocomposites were compared based on four different mechanical treatmentsincluding non-grinding, only grinding, grinding plus sonication and grinding plushomogenization. Results showed that the grinding plus homogenization cellulose/polyurethane nanocomposites exhibited the highest the mechanical property, opticalproperty and thermal stability among these four mechanical treatments.(4) The effects of different HCl concentration and time treatments on theproperties of cellulose nanofiber/polyurethane nanocomposites were investigated.With the increasing of treating time, the mechanical properties, optical propertiesand thermal stabilities of the resulted nanocomposites were first increased thendecreased when the concentration of HCl was1wt%, and gradually decreased when the concentration of HCl increased to2wt%.