Preparation Of Carbon Nanotube/polymer Composite Conductive Material By Colloidal Agglomeration Method

Carbon nanotubes are considered to be an ideal conductive filler to prep are highly electrical conductive polymer composites at lower loadings,according to its high aspect ratio and excellent electrical conductivity.However,aggregates induced by the strong van der Waals forces between the CNTs make them difficult disperse and poorly compatibile with the polymer matrix,resulting in CNTs/polymer composites difficult to achieve the desired performance.Therefore,many studies have focused on the dispersion of CNTs in the polymer matrix,neglecting that the conductivity of composite is mainly related to the construction of the conductive network.In this paper,a simple and effective method,coagulation of colloidal particles,is proposed to control the conductive network of CNTs in polymer matrix by adjusting the electrolyte concentration,thus to prepare highly conductive CNTs/polymer composite.The specific research includes the following aspects:?1?Non-covalent surface modification of MWNTs.MWNTs were dispersed in water with SDS as dispersing agent,bath sonication,probe sonication and high pressure homogenization as dispersing method,and it was found that the best way was to use high-pressure homogenization and only needed 2 minutes.The result of UV-vis showed the optimum dispersion conditions was 1000 bar pressure,8 cycles and the mass ratio of SDS/MWNTs was 1.5,and MWNTs existed in solution as a single carbon tube.The prepared dispersion c ould be stored for at least 45 days,and no settlement occured.However,the conductivity of MWNTs decreased with t he amount of SDS and the cycles of homogenization increasing.Considering the dispersion and conductivity of the MWNTs,the final dispersion conditions were divetermined to be those pressure was1000 bar,cycles of homogenization was 4,and the mass ratio of SDS/MWNTs was 1.5.In addition,PEDOT:PSS conductive polymer and GO as the dispersing agent were studied,respectively.The dispersion effect of MWNTs was investigated under1000bar,4 cycles by high pressure homogenization,the results showed that 0.1wt%MWNTs dispersion was required to only 0.5wt%PEDOT:PSS solution.Electrical conductivity showed that the contact resistance between MWNTs c ould not be significantly reduced because of low PEDOT:PSS conductivity.While the optimal concentration to disperse MWNTs was th e mass ratio of GO/MWNTs=2.5.UV-vis indicated that?-?conjugated interactions existed between GO and MWNTs,and TEM showed that MWNTs adsorb on GO surface.?2?The conductivity of MWNTs/WPU composite prepared b y latex blending method increased with the increasing of MWNTs.The percolation threshold of the composite was 1.2wt%,the conductivity of composite was 0.056S/m when the content of MWNTs was 2.5wt%.Electrolyte concentration could significantly affect the stability of the SDS/MWNTs dispersion.The higher the valence state,caused the lower the CCC value.The CCC values of Na Cl,Ca Cl ₂,and YCl₃ was 200 mmol/L,2mmol/L,and 0.2 mmol/L,respectively.The conductivity of 2.5wt%MWNTs/WPU composites prepared by latex co-coagulation approach increased firstly and then decreased with increasing Ca Cl₂ and YCl₃.The addition of 2 mmol/L Ca Cl₂ and 0.1mmol/L YCl₃ increased the conductivity to 0.407 S/m and 0.442 S/m.While Na Cl only monotonically decreased the conductivity of composites due to the more addition of Na Cl.SEM and TEM images showed that the proper electrolyte addi ng effectively improved the strcture of conductive network of MWNTs.TGA and DTG results showed that the thermal stability of the composite ha d a certain relationship with the formation of the conductive network.?3?MWNTs dispersion with GO as dispersing agent,which was then reducd GO to graphene in RGO/MWNTs/polymer composites systems was studied.The effect of different mass ratios of GO/MWNTs on composites conductivity was investigated.It was found that the conductivity of RGO/MWNTs/WPA composite was best when the mass ratio of GO/MWNTs is 2.5.The XPS results showed the increasing C/O mass ratio indicated that GO was reduced to RGO in the matrix.When the content of MWNTs was 1wt%,the conductivity is 0.538S/m,which was 11 orders of magnitude higher than that of pure WPA.The conductivity of composites can be further improved by coagulation of colloidal particles controlling the formation of RGO/MWNTs gel network in the substrate.The SEM results showed that the conductive network formed in the matrix was not continuous without electrolyte adding,and the appropriate electrolyte will facilitate the formation of the RGO/MWNTs conductive network.TGA and DTG results showed that the addition of MWNTs enhances the thermal stability of the composite compared to pure WPA.