Preparation, Structure And Properties Of Poly(ε-Caprolactone)/Graphene Nanocomposites

In this paper, thermally reduced graphene(TRG) was prepared bymodifying the method as described by Staudenmaier et al. Thermalgravimetric analysis(TGA) and wide angle X-ray diffraction(WAXD) wereutilized in this work to primaryly characterize the TRG. PCL/TRG, PCL/GOand PCL/f-MWCNTs nanocomposites were prepared via a solution mixingmethod in this paper. Firstly, Scanning electron microscopy (SEM) andtransmission electron microscopy (TEM) were used to investigate dispersionof nanofillers and the interface adhesion between nanofillers and the polymermatrix. And various techniques further studied the effects of nanofillers on thecrystallization melting behavior, mechanical properties and thermal stability ofaforementioned PCL nanocomposites. The main research achievements wereshown as follow:Firstly, for the PCL/TRG nanocompsoties system, TEM and HR-TEMobservation reveals that a fine dispersion of TRG has been achievedthroughout the PCL matrix. SEM observation shows not only a nice dispersionof TRG but also a strong interfacial adhesion between TRG and the matrix, asevidenced by the presence of some TRG nanosheets embedded in the matrix.Nonisothermal melt crystallization behavior, isothermal melt crystallizationkinetics, spherulitic morphology, and crystal structure of neat PCL and thePCL/TRG nanocomposites were studied in detail with various techniques. Theexperimental results indicate that both nonisothermal and isothermal meltcrystallization of PCL have been enhanced significantly by the presence ofTRG in the nanocomposites due to the heterogeneous nucleation effect;however, the crystallization mechanism and crystal structure of PCL do notchange. Dynamic mechanical analysis study shows that the storage modulus of the nanocomposites has been greatly improved by about203%and292%,respectively, with incorporating only0.5and2.0wt%TRG at-80oC ascompared with neat PCL.Secondly, for PCL/GO and PCL/f-MWCNTs nanocomposites system,SEM and TEM observations show not only a homogeneous and finedispersion of both GO and f-MWCNTs but also the two differentlydimensional nanofillers morphology in the PCL matrix. The influencesdifferences between GO and f-MWCNTs on the nonisothermal meltcrystallization behavior, isothermal melt crystallization kinetics, spheruliticmorphology, and crystal structure of PCL in the nanocomposites were studiedin detail with various techniques. The experimental results indicate that bothnonisothermal and isothermal melt crystallization of PCL have been enhancedsignificantly in the presence of GO and f-MWCNTs as an effective nucleatingagents; however, the ability of f-MWCNTs in the PCL matrix to accelerate theoverall crystallization rate of PCL is stronger than that of GO in the PCLmatrix. However, the presence of GO and f-MWNTs has not change thecrystallization mechanism and crystal structure of PCL. Finally, dynamicmechanical analysis study not only shows that the storage modulus of thenanocomposites has been greatly improved by about96%and183%forPCL/GO nanocomposite and PCL/f-MWCNTs nanocomposite, respectively,at-80oC as compared with neat PCL, but also demonstrates that thef-MWCNTs is more excellent than the GO nanosheets as a nanofiller in PCLmatrix. The main reasons are because the surface curvature of tubularf-MWCNTs is twice than GO nanosheet.