Preparation And Gas Barrier Property Of Graphite Nanosheet/Polymer Composites

Polymer barriers are widely used in packaging materials and photovoltaics due to their lightweight,low cost,easy processing and high performance.However,Barrier property still need to further improve in order to satisfy the project need.It is an effective way to improve the barrier property by adding graphite nanosheet(GNPs)with large radius-thickness ratio.In this paper,GNPs were modified using different methods,and were used further to prepare nanocomposites using solution blending method.Effects of surface properties of GNPs and polymer structure on microstructure,thermal behavior and gas barrier property of composites were studied in detail.The main contents were as follows:(1)GNPs were modified by oxidation under different oxidizing conditions to obtain oxidized GNPs(O-GNPs)with different oxygen content.Results of FTIR,EPMA and SEM confirmed that the oxygen-containing functional groups on O-GNPs surface are different with the oxidizing conditions,and the oxidation modification does not change the geometric structure of the GNPs.And O-GNPs were blended with polylactic acid(PLA)by solution blending method to obtain(O-GNPs/PLA).SEM,DSC,pressure difference method were used to characterization the composite microstructure,thermal behavior and gas barrier property.The results show that the oxidation can improve the dispersion of GNPs in PLA matrix,and reduce obviousely the oxygen permeability coefficient,indicating that oxidation can increase the enhancing effect of GNPs on PLA barrier property.Moreover,with the increasing oxygen of O-GNPs surface,the enhancing effect of GNPs on PLA barrier performance is more obvious.(2)GNPs were modified using tannic acid to prepare the modified graphite nanosheets(TA-GNPs).The results of FTIR,EPMA and SEM confirmed that tannic acid was adsorbed stably on the GNPs surface,moreover,the adsorbed tannic acid doesn't change the geometric structure of the GNPs.TA-GNPs was further blended with PLA to prepare nanocomposites(TA-GNPs/PLA).SEM,DSC,pressure difference method were used to characterization the composite microstructure,thermal behavior and gas barrier property.The results show that tannic acid can improve the dispersion of GNPs in PLA matrix,and further increase the enhancing effect of GNPs on the PLA barrier property.Incorporating 0.50wt% TA-GNPs into the PLA,reduced the oxygen permeability by 50.15% compared with the pure PLA.(3)GNPs were further modified using dopamine on the base of dopamine chemistry to poly(dopamine)modified graphite nanosheets(PDA-GNPs).The results of FTIR and SEM demonstrated that poly(dopamine)was coated on the GNPs surface,and the modification of poly(dopamine)did not change the geometric structure of GNPs.PDA-GNPs was blended with polyvinylidene fluoride(PVDF)and PLA,respectively to prepare two kinds of nanocompostes(PDA-GNPs/PVDF and PDA-GNPs/PLA).and the microstructure,thermal behavior and gas barrier property of nanocomposites were characterized and tested.The results indicated that the polydopamine modification can improve the dispersion of GNPs in PVDF and PLA in the matrix,further increase the enhancing effect of GNPs on PVDF and PLA oxygen barrier property.Incorporating 0.50wt% PDA-GNPs into the PVDF,reduced the oxygen permeability by 71.51% compared with the pure PVDF.Incorporating 1.00wt% PDA-GNPs into the PLA,reduced the oxygen permeability by 83.00% compared with the pure PLA...