The Preparation And Properties Of Functionalized Graphene/polypropylene Nanocomposites

Graphene,which was found since 2004,has attracted wide attention due to its excellent performance.Especially graphene that was used in fabrication of polymer nano-composites is one of becoming the most important hot spots throughout the world.In recent years,a large number of studies have shown that the performance of the polymer based nanocomposites is better than that of the pure matrix by adding the functionalized graphene.However,there are two major problems should be solved in graphene/polymers composites:one is the dispersion of graphene in the polymer matrix,and the other is improving interfacial bonding strength between graphene and polymer.This paper is divided into four parts:In the first part,graphite nanosheets/polypropylene(PP)composites were prepared.Specifically,first graphite micro sheet(EG)was prepared by intercalation-reducing method,thermal reduction micro sheet(T-rGO)was obtained by thermal reduction of graphene nanoplatelets,and chemical reduction micro sheet(C-rGO)was prepared through chemical reduction of graphene nanoplatelets,respectively.Then PP based composites,including PP/EG,PP/T-rGO and PP/T-rGO composites were prepared via melt blending route by using the above three kinds of graphite microsheets.The surface structure and properties of the filler were studied by X-ray diffraction(XRD)and scanning electron microscopy(SEM).The microstructure,mechanical properties and thermal properties of the composites were analyzed by SEM,electronic universal tensile testing machine,differential scanning calorimeter(DSC)and thermogravimetric analyzer(TG).The results of XRD and SEM analysis showed that the order of the interlayer spacing between the three different graphite microsheets was C-rGO>T-rGO>EG,and the degree of exfoliation of graphene nanosheets(C-rGO)prepared by chemical reduction method was the most complete.Tensile properties analysis showed that the tensile strength of PP/C-rGO composites reached 37.3MPa when the content of C-rGO was 0.3wt.%,which was increased by 24%,30%and 65.7%,respectively,compared with pure PP,PP/EG and PP/T-rGO composites.The DSC analysis showed that the crystallinities of PP/EG,PP/C-rGO and PP/T-rGO composites were higher than that of pure PP.In case of PP/C-rGO composite,the crystallinity of PP/C-rGO reached 46.9%,which is increased by 3.32 when compared with that of pure PP at the C-rGO content of 0.1 wt.%.The crystallization temperature and melting temperature were 110.8℃ and 164.9℃,respectively,which increased slightly compared with those of the pure PP.TG analysis showed that when the content of graphite sheet was 0.1 wt.%,the initial decomposition temperature of PP/EG,PP/T-rGO and PP/C-rGO were 451.5℃,447.1℃ and 444.9℃;and the maximum decomposition temperature were 454.3℃,463.6℃ and 462.7℃.They all showed increasing tendency when compared with the pure PP.In the second part,graphene/nano-silica/PP nano-composites were prepared.Specifically,first three different methods were used to prepare nano-silica modified graphene oxide respectively:(1)by a hydrothermal method(HGS),(2)by sol-gel method(SGS),(3)by in-situ grafting(GOS).The PP/HGS,PP/SGS and PP/GOS nanocomposites were then fabricated by melt blending.The contents of three kinds of fillers were 0%,0.1%,0.3%,1%and 2 wt.%,respectively.The microstructure,mechanical and thermal properties of the three kinds of composites was tested.The tensile and impact properties analysis showed that when the three kinds of content of nano-silica/graphene hybrids were 0.1 wt.%,the tensile strength of PP/HGS,PP/SGS and PP/GOS nanocomposites were 37.86MPa,38.89MPa and 36.94MPa,respectively,which increased by 25.9%,29.3%and 22.8%in constract to the pure PP;the impact strength was 5.6 kJ/m2,7.6 kJ/m2 and 7.7 kJ/m2,respectively,increasing by 22.6%,66.4%and 68.6%compared with the pure PP.The results of SEM analysis showed that when the filler content was low,it could be dispersed uniformly in the matrix.In the third part,graphene/styrene butadiene rubber(SBR)/polypropylene(PP)composites were prepared.In the first step,the SBR/PP composites were prepared and tested,and the appropriate SBR content was determined.Then,the C-rGO(based on Chapter Ⅱ)was selected and added into the SBR/PP composite,and finally the PP/SBR/C-rGO composites were prepared by melt blending method.The testing on the mechanical properties of PP/SBR composites showed that when the content of SBR was 10 wt.%,the toughness of the composites increased by 28.75 MPa but the strength decreased by 7.86 kJ/m2,compared to pure PP.Based on this result,PP/SBR/C-rGO nanocomposites was prepared at the content of SBR of 10 wt.%,and C-rGO of 0%,0.25%,0.5%,1%and 2 wt.%,respectively.The results showed that when the content of C-rGO was 0.5 wt.%,the tensile strength and impact strength of PP/SBR/C-rGO composites were 31.05MPa and 8.6 kJ/m2,respectively,which were improved by 8%and 9.4%,respectively,compared with the PP/SBR.Although the increasing in tensile strength was not significant compared with pure PP,the impact strength was increased by 88.35%.Dynamic mechanical analysis(DMA)showed that the storage modulus of the composites was improved,and the peak value of the loss modulus also moved to the higher temperature.In the fourth part,graphene/halloysite nanotubes were firstly prepared and then used in the graphene/halloysite nanotubes/PP nano-composites.The detailed procedure is depicted as follows:using tannic acid(TA)modified graphene oxide(GO)to produce TANGO hybrid(TAG),and then HNTs-TAG hybrid was synthesized by compounding halloysite nanotubes(HNTs)with TAG to get the final hybrid filler(HNTs-TAG).PP/H-NTs-TAG nanocomposites were then obtained by melting compounding.HNTs-TAG content in the composite was 0,0.25,0.5,1 and 2 wt.%.The results showed that when the HNTs-TAG content was 0.5wt.%,the tensile strength and impact strength of the nanocomposites increased to 35.34MPa and 8.24 kJ/m2,which increased by 17.5%and 180%compared with pure PP.DSC test showed that the melting temperature and crystallization temperature were better than that of pure PP.When the HNTs-TAG content was 0.5wt.%,the melting temperature and the crystallization temperature were 114.9℃ and 164.9℃ respectively,increasing by 6.1℃ and 1.9℃ compared with the pure PP.SEM showed that when the content of HNTs-TAG was low,the filler is dispersed uniformly in the matrix,and the agglomeration appeared at high HNTs-TAG loading.