The Construction And Performance Of Conductive Network In Natural Rubber By SiO₂/CNT Effective Hybrid

The complex entanglement and strong?-?stacking interaction between multi-walled carbon nanotubes(MWCNTs)make it difficult to uniformly disperse in the polymer matrix.The traditional polymer processing technology is difficult to prepare polymer/multi-walled carbon nanotubes(MWCNTs)nanocomposites with high performance,multifunction and low filling amount.Based on this situation,we prepared m-SiO₂/MWCNTs hybrid filler(ISMH)by using the volume exclusion effect of silica microspheres(m-SiO₂)and the interfacial strengthening effect of tannic acid(TA),so as to realize the uniform dispersion of m-SiO₂ and MWCNTs in the matrix.On this basis,m-SiO₂@Ag/MWCNTs hybrid filler(ISSMH)was prepared by metallization of m-SiO₂surface,and the effects of ISMH and ISSMH on the properties of natural rubber matrix composites were systematically studied.First,we prepared a m-SiO₂/MWCNTs hybrid filler(ISMH).The filler was not only easily dispersed in the rubber matrix through mechanical blending,but also formed a bionic interface with the rubber matrix through natural tannic acid(TA).Due to the volume exclusion of m-SiO₂,a small amount of MWCNTs can form a dense three-dimensional network structure in natural rubber(NR)matrix,which makes NR/ISMH nanocomposites have high functionality.When the MWCNTs loading was 0.33 phr,the conductivity of NR/ISMH nanocomposites reached the equilibrium value of 10^-4 S·cm^-1.In addition,NR/ISMH nanocomposites also have excellent mechanical properties.When the loading of ISMH-30 was 20 phr,the tensile strength,tear strength,elongation at break and DIN wear of the composite were 28.7 MPa,43.7 N·mm^-1,625%and 0.18 cm³,respectively,which were changed by+58%,+16%,+11%and-31%compared with pure NR matrix.Secondly,we carried out surface metallization of m-SiO₂.Silver-plated m-SiO₂microspheres(m-SiO₂@Ag)core-shell composite particles were prepared by two-step method of dopamine surface modification and electroless silver plating.The effects of different processes on the core-shell structure were studied,and m-SiO₂@Ag/MWCNTs hybrid filler(ISSMH)was prepared.m-SiO₂@Ag has become a part of the entire conductive network within the composite.As the hub of the conductive path,it provides more electronic transmission paths,thereby improving the conductive efficiency of the material.The experimental results show that the maximum volume conductivity of ISSMH can reach 0.38 S·cm^-1.The volume conductivity of NR/ISSMH nanocomposites prepared under these conditions reached 1.8×10^-2 S·cm^-1,which was increased by two orders of magnitude compared with that before silver plating.Finally,the effect of ISSMH on the properties of natural rubber matrix composites was studied by control variable method.It was found that the platform conductivity of NR/ISSMH nanocomposites reached 10^-1 S·cm^-1,which was three orders of magnitude higher than that of NR/ISMH nanocomposites.At the same dosage,the thermal conductivity of the composite is improved more by ISSMH than by ISMH,and the thermal conductivity of NR/ISSMH nanocomposites is higher than that of NR/ISMH nanocomposites regardless of the filling ratio.The study on mechanical properties found that a small amount of ISSMH has a positive effect on the tensile and tearing properties of the composites,but with the increase of the amount of ISSMH will eventually lead to the decline of the physical and mechanical properties of the composites.