Preparation Of High Performance Conductive Natural Rubber Nanocomposites Based On Filler Hybridization Strategy

Carbon-based nanomaterials such as conductive carbon black,graphene and carbon nanotubes are often used to prepare conductive elastomeric composites due to their excellent electrical conductivity.However,the preparation of conductive polymer composites relying only on a single filler often needs to be accompanied by a high filling amount to achieve the established effect,which will inevitably lead to a significant reduction in mechanical properties,increased processing difficulties,and further increase the preparation cost.Studies have shown that the combination of multiple fillers can produce significant synergistic effects in improving the comprehensive performance of nanocomposites,effectively improving the electrical and mechanical properties of polymers and reducing the complexity of the process,which has a broad development prospect.Therefore,this thesis investigates the construction of conductive networks in natural rubber by selecting suitable fillers,compositional optimization of composite conductive fillers and microstructural modulation.The aim is to develop high performance/low cost flexible conductive elastomers,and the selected topic has good practical value.In the first part,by examining the effects of various industrial carbon black fillers and different secondary fillers on the electrical conductivity and mechanical properties of natural rubber,it was found that carbon black(N234),which has smaller particle size and higher structure,is suitable as a base filler for building a conductive network.Carbon nanotubes(CNTs)and tannic acid liquid-phase exfoliated graphene(TGE)as secondary conductive fillers help to construct conductive and thermally conductive networks in rubber and achieve high electrical and thermal conductivity.It is worth noting that,compared with other conductive carbon materials,TGE is simple to prepare,green and environmentally friendly,with lower cost and conductive properties comparable to the addition of CNTs secondary fillers,so it is expected to replace expensive conductive carbon materials.In the second part,effective hybrid fillers(TGN)with different hybridization rates were prepared using tannic acid(TA)interfacially coupled large-size silicon microspheres(N98)and graphene(GE).The volume repulsion of N98 and the interfacial enhancement of tannic acid improve the dispersion of graphene,giving the best overall performance of rubber and significantly improving the electrical and thermal conductivity of rubber.The results showed that the bulk conductivity of NR/TG₁N₂₀nanocomposites reached an equilibrium value of 10^-3 S·cm^-1 with good electrical conductivity when the GE filling amount was 0.48 phr.In addition,the strong interface formed by TA bridging between N98 and GE through non-covalent bonds not only determines the stability of the conductive network,but also attenuates phonon scattering and interfacial thermal resistance,which enables the NR/TGN composite to obtain excellent electrical properties while effectively improving thermal conductivity and providing it with good processability and dynamic and static mechanical properties.Based on the preparation of TG₁N₂₀ effective hybrids in the second part,in the third part,composite fillers were produced by grafting and hybridizing with tannic acid functionalized conductive carbon materials(GE and CNTs)using mimetic dopamine-coated modified N98 silicon microspheres to reduce their aggregation tendency while functionalizing N98 with abundant reactive groups on its surface.N98 silicon microspheres,tubular CNTs,and sheet GE bridge each other to form a three-dimensional conductive network,further improving the thermal and electrical conductivity of the rubber.The results showed that the nanocomposites filled with hybrid filler(TCGN@PDA)prepared with N98 hybrid carbon material functionalized with dopamine outperformed the nanocomposites filled with hybrid filler(TCGN)prepared with N98hybrid carbon material without dopamine functionalization in all properties(electrical and thermal conductivity,dynamic and static mechanical properties,and processing properties),especially in electrical and thermal conductivity.In addition,comparing the effects of the hybrid fillers filled with different hybridization ratios on the properties of the NR composites,it can be seen that the comprehensive performance of the nanocomposites filled with TC_0.5G₁N₂₀@PDA hybrid fillers is optimal.