Study On The Enhancement Law Of Conductivity Of Polymer-based Conductive Composites By Spacial Confining Forced Network Assembly

At present,there are mainly three methods for constructing a polymer-based composite material by constructing a conductive network,which are an in-situ polymerization method,a solution mixing method,and a melt mixing method.All of the above three methods form a network in the matrix material through the self-assembly mechanism.When the material reaches the percolation threshold,the conductivity of the material can only be improved by increasing the concentration of the filler.However,due to insufficient self-assembly,the conductive network is not dense enough.The conductivity of the composite is still not ideal.In order to further reduce the percolation threshold of polymer matrix composites and improve the electrical conductivity of composites,this paper is based on Spacial Confining Forced Network Assembly method(SCFNA)to prepare composites with different types of materials as matrix.The SCFNA method compacts the conductive network by limiting the compression in one direction,forming a conductive path,reducing the material percolation threshold,and improving the electrical conductivity and mechanical properties of the composite.The main research contents are as follows:(1)EVA/SCF conductive composites were readied through SCFNA,and the percolation threshold of EVA/SCF samples with thickness of 0.1mm was 6.5wt%,which was lower than the percolation threshold of 8.2wt%under blending method.Through the conductivity test of the sample,the relationship between the concentration of different carbon fibers and the ratio of forced compression to the electrical conductivity of the composite is obtained.And the mechanical properties of the composites under each mass fraction were tested.It was found that the tensile strength of the 10wt%EVA/SCF composite was the highest,and the highest was 19.86MPa.(2)The SCFNA method can not only improve the electrical conductivity of the elastic-like material,but also improve the electrical conductivity of the thermoplastic matrix linear low-density polyethylene(LLDPE).The conductive filler is still chopped carbon fiber(SCF),and the electrical conductivity and mechanical properties of the LLDPE/SCF sample were tested.The percolation threshold of the 0.1 mm thick LLDPE/SCF composite prepared by the SCFNA method was found to be 8.3 wt%.The SCFNA method has a conductivity of up to three orders of magnitude higher than that of the sample prepared by the blending method.And with the increase of SCF content,the electrical conductivity of LLDPE/SCF composites is getting better and better.When the SCF content is 18wt%,the mechanical properties of the composite are the best,and the tensile strength reaches 22.03MPa.(3)The ternary conductive filler was prepared by the SCFNA.The thermosetting material polydimethylsiloxane(PDMS)was used as the matrix,and the short carbon fiber(SCF)and carbon nanotube(CNT)were used as the conductive filler.Change the ratio of the two fillers while the total filler content is constant.It was found that the conductivity of the composites was greatly improved after adding a small amount of CNT to the PDMS/SCF.However,if too many CNT were added,the electrical conductivity and mechanical properties of the PDMS/SCF/CNT composites decreased.