Fabrication And Properties Of Graphene/Polymer Electrically Conductive Nanocomposites

Graphene has excellent electrical conductivity so as to act as a filler for conductive nanocomposites.However,the difficulty of large-scale preparation of graphene and the problems of easy agglomeration in polar polymers have become major obstacles to the preparation of composites with excellent properties.Graphene oxide?GO?is generally considered as the precursor of graphene,and it is an effective method to simultaneously reduce and modify the surface of GO to promote its dispersion in polymer matrix.In this article graphite oxide is produced by improved Hummers method,and then it is reduced and modified at the same time by p-phenylenediamine or nano-silver,finally,they are added respectively as conductive filler to polyethylene terephthalate?PET?and polystyrene?PS?.The works and results are started as below:As a result of the nucleophilic substitution reaction between amine and epoxy groups,p-phenylene diamine?PPD?is considered to be the reducing and functionalizing agent of graphene oxide in an aqueous medium with ammonia,ultimately functionalized graphene?f-RGO?is prepared.P-phenylenediamine achieves effective intercalation between graphene oxide sheets,and a variety of characterization methods indicate that graphene oxide is effectively reduced.It is found that the graphene layer spacing increased from 0.81 nm for GO to 1.49 nm for f-RGO,the number of oxygen-containing functional groups in GO is reduced,and the p-phenylenediamine chain is successfully grafted.The conductivity of f-RGO at room temperature is 1.8×10² S·m^-1,which is much higher than that of GO.In addition,the thermal stability of f-RGO has also been improved.The graphene/polyethylene terephthalate nanocomposite is prepared by adding f-RGO to the PET by melt blending,and then the nanocomposite with good conductivity is obtained by hot pressing.By changing the content of graphene in PET,different ratios of graphene/polyester nanocomposites were obtained.As a result,it was found that f-RGO was well dispersed in PET and the thermal stability of the composite was significantly improved.When the content of graphene is 3.07 vol.%,the bulk conductivity of the composite reached 6.34×10^-4 S?m^-1 at room temperature.And the conductive percolation threshold is 0.61vol.%.The more the graphene content is,the higher the electrical conductivity of the composite is.The well-dispersed modified graphene can significantly increase the electrical conductivity of the composite.Besides,under mild conditions,graphene/silver nanocomposites?RGO/Ag?are prepared by reducing GO and silver ions simultaneously with glucose.In the experiment,polyvinylpyrrolidone?PVP?is used as a protective agent and silver ammonia solution provides silver ions.The results show that the number of the oxygen-containing group of GO is reduced,and the silver nanoparticles are successfully coated on the surface of graphene.The size of silver particles varies from 35 to 100 nm,and GO and silver ions are successfully reduced by glucose.The conductivity of RGO/Ag is 5.4×10³ S?m^-1,and the thermodynamic stability is higher than that of GO.Add RGO/Ag as a filler to the PS by solution blending and the conductive nanocomposites are prepared.The results show that RGO/Ag is uniformly dispersed in the PS matrix.The electrical conductivity and thermal stability of composites both are improved.It shows low percolation threshold and good conductivity.Conductive percolation threshold is 0.29vol.%.When the volume fraction of RGO/Ag is 2.03 vol.%,the volume conductivity of the composite reaches 8.61×10⁰ S?m^-1.