Preparation And Properties Of Graphene/Carbon Nanotubes/Polymer Nanocomposites

Graphene and carbon nanotubes are becoming the current hot research topic in the field of nanometer materials due to they show excellent mechanical,thermal and electrical performance.Using graphene or carbon nanotubes as filler in the preparation of polymer nanocomposites has received much attention and much progress has been achieved in the previous works.However,how to improve the dispersion of fillers,as well as improve the interfacial strength in the nanocomposites are still two important issues.Recently,it has been proved a three dimensional space structure will be formed when using graphene and carbon nanotubes simultaneously because of unique structure characteristics and spatial configuration of graphene and carbon nanotubes,and as a result,a synergistic effect will be realized.This kind of composite material has showed excellent performance which a single graphene or carbon nanotubes material does not have,resulting in it widely applied to the super capacitor,solar cells,biological detection,and the preparation of polymer-based nanocomposites,and other fields.This paper includes three parts:The first part is the fabrication of ethylenediamine functionalization graphene（GS-EDA）/acidification of multi-walled carbon nanotubes（MWCNTs-COOH）/polystyrene grafted maleic anhydride（PS-g-MAH）nanocomposites.In the experiment,the total weight content of GS-EDA and MWCNTs-COOH is fixed at 0.5 wt%.The mass ratio of GS-EDA and MWCNTs-COOH is 0:1,1:1,1:2,2:1,1:0.The surface structure and property of the functional filler were characterized by using infrared spectrum（FTIR）and X-ray diffraction（XRD）.The microstructure,mechanical and thermal properties of the nanocomposite were investigated by using scanning electron microscopy（SEM）,tensile tests,impact tests,DSC and thermal gravimetric（TG）analysis.FTIR and XRD indicated that EDA has been grafted on the graphene oxide sheets,and–COOH group has been introduced into MWCNTs during acidic treatment.Tensile test showed that when graphene and carbon nanotubes were added simtaneously,the tensile strength of the nanocomposites is higher than those of nanocomposites filled by using only graphene or carbon nanotubes filler.When the mass ratio of GS-EDA/MWCNTs-COOH was 1/2,the tensile strength and the elastic modulus improved by 16%and 28%,respectively when compared with pure PS-g-MAH.DSC analysis showed that the glass transition temperatures（T_g）of GS-EDA/MWCNTs-COOH/PS-g-MAH nanocomposites were higher than both those of nanocomposites filled by using only graphene or carbon nanotubes filler and pure PS-g-MAH,When the mass ratio of GS-EDA/MWCNTs-COOH was 1/1,the T_g improved by 6.3 ^oC,respectively when compared with pure PS-g-MAH.TG analysis showed that the maximum thermal decomposition temperature of GS-EDA/MWCNTs-COOH/PS-g-MAH nanocomposites was higher than those of nanocomposite modified by single filler,and is higher than pure PS-g-MAH.When the mass ratio of GS-EDA/MWCNTs-COOH was 1/1,the T_max improved by 4.6^oC,respectively when compared with pure PS-g-MAH.The second part is prepareation of high density polyethylene-g-maleic anhydride（HDPE-g-MAH）based nanocomposites filled with GO-EDA and MWCNTs-COOH by melt compounding method.In the experiment,the ratio of ethylenediamine functionalization graphene oxide（GO-EDA）and MWCNTs-COOH is 1:1.The mass content of fillers is 0 wt.%,0.25 wt.%,0.5 wt.%,0.75 wt.%and 1 wt.%.The synergistic strengthening-toughening effects of（GO-EDA+MWCNTs-COOH）hybrid fillers on the HDPE-g-MAH were investigated by tensile tests,impact tests,SEM、dynamic mechanic analysis（DMA）and TG analysis.Tensile and impact tests indicated that that the mechanical properties of the nanocomposite were improved obviously when（GO-EDA+MWCNTs-COOH）hybrid fillers were incorporated simultaneously.When the hybrid fillers was 0.5 wt.%,the tensile strength increased by 16%,while impact strength increased by 20%at the hybrid fillers content of 0.75 wt.%,when compared to pure HDPE-g-MAH.SEM observations showed that（GO-EDA+MWCNTs-COOH）hybrid fillers have been dispersed homogeneously into HDPE-g-MAH matrix.DMA analysis indicated that,when（GO-EDA+MWCNTs-COOH）hybrid fillers were incorporated,the storage modulus of composites was higher than that of pure HDPE-g-MAH matrix,the peak of loss modulus shifted to higher temperature.The TG and DSC analysis indicated the thermal stability properties of composites was improved as well.In order to improve the interfacial strength in the nanocomposites,a novel monomer,L-aspartic acid was selected to functionalized GO-EDA,followed by synthesizing functionalized GO-EDA/MWCNTs-COOH（LGC）hybrid nanomaterials.Then nanocomposites of HDPE-g-MAH synergistic strengthening-toughening using LGC hybrids were prepared via melt compounding method.The surface structure of LGC was characterized by using infrared（FTIR）and Raman spectrum.The synergistic strengthening-toughening effects of LGC hybrids on the HDPE-g-MAH were investigated by scanning electron microscopy（SEM）,dynamic mechanical analysis（DMA）,thermal gravimetric（TG）analysis,tensile and impact tests.FTIR showed that the L-aspartic acid connected GO-EDA and MWCNTs-COOH through chemical bonds.SEM observations showed that LGC hybrids were homogeneously dispersed in HDPE-g-MAH composites.Tensile and impact tests indicated that the mechanical properties of the nanocomposites were improved obviously when LGC hybrid nanomaterials were incorporated simultaneously.The tensile strength of LGC/HDPE-g-MAH nanocomposites containing 0.75 wt.%LGC was 19%higher than that of pure HDPE-g-MAH,while the impact strength was 25%higher than that of pure HDPE-g-MAH when 0.5 wt.%LGC was incorporated.It is better than nanocomposites in the second part that adding（GO-EDA+MWCNTs-COOH）at the best filler content.DMA analysis indicated that the storage modulus of composites was higher than that of pure HDPE-g-MAH matrix.TG analysis results revealed that the maximum decomposition temperature of HDPE-g-MAH composites containing 0.75 wt.%of LGC showed 8 ^oC higher than that of HDPE-g-MAH matrix.The DSC analysis showed that the melting peak was increased.