Graphene Oxide Prepared From Biomass Carbon And Study On The Modification Of Polybenzoxazine By Graphene Oxide And Isocyanato-terminated Polyurethane Prepolymer

Graphene oxide(GO),as a new carbon material,possessing unique structure and excellent properties,is widely applied.With the increasing awareness of environmental protection,it has attracted increasingly widespread attention for research based upon various other eco-friendly carbon sources that can be readily tailored to GO.Benzoxazine,as a novel class of high performance phenolic resin,has the broad application prospect.However,the application of polybenzoxazine is limited due to its rather high brittleness and difficulty in processing.In this paper,the purpose of our investigation is as follows:preparing GO based upon biomass material,as the structure and properties were characterized,would provide a new thought from the other eco-friendly reproducible carbon materials for preparation of GO.Flexible ternary/binary aliphatic benzoxazines and their copolymers,poly(benzoxazine-urethane)/graphene oxide composites,as well as functionalized graphene oxide/flexible polybenzoxazine composites were prepared,and then the structure,morphology and properties were characterized,that would obtain the data for improving polybenzoxazine and the application of GO in the polymer.The main contents and the results of the dissertation are as follows:1.Preparation and characteristics of graphene oxide from the biomass carbon materialGO was successfully prepared via Hummers method from the graphitization carbon based upon biomass material using fir powder as precursor,which was named as FPGO.As comparison to verify the successful synthesis of FPGO,GO from expanded graphite(named as EGO)was prepared.FPGO had the typical characteristics of GO,possessing the grossly close nanostructures and comparable element constitutions with EGO.XRD proved that the interlayer spacing corresponding with(001)diffraction peak of FPGO was 8.5 A,close to 9.1 A of EGO.The FTIR and XPS analyses indicated five different oxygen-containing functional groups existing between the FPGO nanosheets.The stacked layer structure and the lattice distortions of the FPGO basal planes were confirmed by LR.The AFM image directly observed that the FPGO nanosheets were single layer thick and lateral dimensions in the range of about one to several micrometers in diameter.FPGO had a wrinkled morphology and layer structure intuitively observed from the FESEM and TEM images.The TGA curves reflected that FPGO had close contents of oxygenated groups with EGO,leaving the same residual carbon element of about 49 wt.%at 900 ? in nitrogen atmosphere.2.Studies of flexible aliphatic ternary/binary benzoxazines and their copolymers:preparation,mechanical and thermal propertiesAliphatic ternary benzoxazine,as well as flexible binary benzoxazine,based from triamine and diamine with long chain,phenol and paraformaldehyde was successfully synthesized,which was named as BzT and BzD,respectively.The corresponding polybenzoxazines rooting from BzT and BzD(PBzT and PBzD)respectively and their copolybenzoxazines(co-PBzs)were obtained to improve the mechanical and thermal properties via chemical cross-linking.The onset polymerization temperatures of the copolymers decreased from 189.1 ? to 143.9 ?,and the exothermic peak temperature reduced significantly from 232.5 ? to 217 ? as the content of BzT increased from 0 to 100 wt.%in the copolymers.The value of char yield at 800 ? in nitrogen atmosphere increased gradually from 21.5 wt.%for PBzD to 28.7 wt.%for PBzT.The increasing crosslink density resulted higher glass transition temperatures and improved storage moduli in glassy region because of the introduction of BZT.3.Preparation and characteristics of poly(benzoxazine-urethane)/graphene oxide composites:mechanical and thermal propertiespoly(benzoxazine-urethane)/graphene oxide[poly(Bz230-PU)/GO]composites were successfully prepared by blending benzoxazine(Bz230)with GO and isocyanato(NCO)-terminated polyurethane prepolymer(PU),followed by thermally activated polymerization of the blends.The network was formed via the mutual reaction and intermolecular interaction among the hydroxyl groups of GO,NCO groups of PU and phenolic hydroxyl of Bz230.The toughness shown from FESEM images and stress-strain curves of polybenzoxazin.e plastic composites from tensile tests can effectively be improved by alloying with PU and GO.The onset curing temperature and exothermic peak maximums of the polymerization obtained from DSC decreased resulted from the GO addition.The TGA analysis showed that the incorporation of 0.5 wt.%of GO slightly improved the thermal stability of poly(Bz230-PU)/GO composites.The storage modulus improved and the glass transition temperature(Tg)increased gradually as the increasing GO content not beyond 3 wt.%amount.Additionally,the exothermic peaks of the polymerization were shifted to lower temperature,and the thermal stability increased for the ternary composites as the number average molecular weights(Mn)of polyol decreased.4.Preparation and thermal properties studies of polyether amine(PEA)modified graphene oxide and its benzoxazine compositesGO was functionalized by PEA via two methods which were one-pot modification in solvent(GON)and two steps with the intermediate product of GOCO-Cl generated(GONS).The structure characterized by XRD,FTTR,XPS and LR certificated that there were more PEA successfully grafted onto GO for GONS than GON.TGA and micrographs verified the interaction between GO and PEA.Thermal property of benzoxazine was greatly influenced by the presence of GON and GONS.The onset polymerization temperatures of the composites obtained from DSC decreased by the inclusion of 1 wt%of GO,GON or GONS.Thermal stability of the polybenzoxazine composites was significantly improved indicated from the increase of weight loss temperature shown from TGA analysis.T10,T20 and T50 values of the composites with GONS were higher than that of the other materials.Toughness of polybenzoxazines may be enhanced by the incorporation of nanofillers,and GONS had stronger interfacial interaction with the matrix than GON.