Preparation And Conductivity Of CNTs/CF/PDMS Flexible Conductive Composites

There is good flexibility and conductivity of flexible conductive composites.Under external stress,there will be changes in the resistance,thus having greater potential in wearable electronic devices and foldable electronic screens.In order to reduce the content of conductive filler and increase the flexibility of the composites,hybrid fillers CNTs and CF were chosen to be filled into PDMS to fabricate composites by solution blending method,surface modification method and swelling permeation method.And explore the effect of surface modification and swelling permeation on the conductivity and strain sensitivity of the material.The main work of this paper are as follows:The CNTs/CF/PDMS flexible conductive composites were prepared by solution blending method.The results show that the direct current?DC?of composite reached the lowest at 6/4 of CNTs/CF,which is 1.79?·m.The composites had the highest critical point frequency in the alternating current?AC?,and the minimum resistivity in the low frequency region.The E'and?of the hybrid filler composites are larger than the sum of the single filler composites.The AC,rheological and morphological measurements were performed and the results presented the existence of synergistic effect between the hybrid fillers.The tensile strain of the composites exceeded 150%,?R/R₀ exceeded 300%and representing strain sensitivity.The?R/R₀ tended to be stable with the increasing number of stretching cycles.CNTs was modified by SCA?called m-CNTs?and m-CNTs/CF/PDMS composites were prepared by solution blending.The results show that the DC resistivity of the composite increased,the critical point frequency of the AC curve decreased slightly,and the AC resistivity in the low frequency region increased.The SEM results showed that the m-CNTs were more uniformly dispersed in the matrix,and rheological results showed that the E'and?of the composites increased than the CNTs/CF/PDMS composites.The?R/R₀ and the GF of the composites increased obviously,which indicates that the modification of SCA improved the dispersion of CNTs in the matrix and promoted the formation of conductive network.The CNTs/CF/PDMS composites were prepared by swelling penetrating method.The optimal experimental conditions for the preparation of composites were as follows:the ratio of PDMS to crosslinker was 20:1,thes welling time of CF/PDMS was 1h,the swelling solvent of PDMS was hexane;the solvent for preparing CNTs suspension was the mixture of DMF and deionized water?volume ratio 1:4?,the optimum concentration of the suspension was 1.5 mg/mL,the best infiltration time was 3 h,and the optimal temperature was 70°C.Based on the above conditions,the effect of infiltration temperature on the electrical properties of composites was studied.The results showed that the composite material with the infiltration temperature of70°C has the lowest DC resistivity,the AC curve has the highest critical point frequency,and the lowest AC resistivity in the low frequency region.SEM results showed that CNTs were concentrated on the surface layer of PDMS with less internal penetration but not only adhered to the PDMS surface.The tensile strain of the composite can reach 250%,the minimum?R/R₀ reaches 400%,and the sensitivity is better.The strain sensitivity and responsiveness of the composites are better,the maximum and the minimum?R/R₀ remained basically unchanged,and the stability and circulation of the material were excellent.