Fabrication Of Flexible CNTs/BMI Structure And Properties Using UV-assisted 3D Printing

Conductive polymer/functionalized conductive structure has become a major milestone in the material revolution of the new era,but so far,some polymer substrates with good performance are not compatible with 3D printing due to their own structure,and most flexible conductive polymers have reached the bottleneck in mechanics.In this case,in addition to high sensitivity and functionality,polymer conductive structures with good mechanical properties have become the main research direction at present.In this experiment,we designed a new type of flexible bismaleimide structure as the polymer substrate of the functional conductive structure using biphenylenedicarboxylic anhydride,self-made long-chain diamine and maleic anhydride.¹³C NMR and FTIR showed that we synthesized the expected structure.Rheological data can show that the viscosity of flexible bismaleimide monomer has a good temperature dependence,ensuring that it will not gel,and the minimum viscosity can reach 15 Pa.s.DSC results show that the curing exothermic enthalpy is 139.6 J/g,which has good reactivity;When the temperature is raised again,it has a typical glass transition peak,Tg is 41.7℃,which is beneficial to the shape memory process.DMA results show that the storage modulus at room temperature is about 100 MPa,with good flexibility.TGA showed that the bismaleimide after thermal curing had very good thermal stability,T_5%was 415℃.In addition,the shear test can show that the monomer has high toughness.After characterizing the basic properties,we carry out UV curing treatment on it.The results show that the tensile strain does not decay after UV curing at room temperature compared with heat curing;At 100℃,due to the different curing methods,the tensile strain is slightly lower than that of the heat-cured sample,with a attenuation of 12%.In general,the synthesized flexible bismaleimide monomer is very suitable for the polymer substrate of functional shape memory conductive materials.Finally,we used bismaleimide as the substrate,and treated it by UV curing.CNTs/BMI was obtained by using 2%,5%and 10%carbon nanotube dispersion for ultrasonic impregnation.XRD and XPS showed that with the increase of the concentration of the dispersion,the diffraction peak of CNTs/BMI surface gradually increased,and the content of surface carbon elements increased;In addition,SEM can show that the arrangement of carbon nanotubes on the surface tends to be regular with the increase of impregnation solution concentration.The strain of the three CNTs/BMI structures reached 600%at room temperature,and the electrical response sensitivity of CNTs/BMI-3 was the highest during the tensile process;At 100℃,CNTs/BMI-3showed sensitivity different from room temperature,and the tensile sensitivity increased by 1027%.In addition,the electrical response stability tests of CNTs/BMI-3 at room temperature and 100℃can show that it has good electrical response stability under both environmental conditions.Under the same strain,the sensitivity of CNTs/BMI-3 at 100℃stretching can reach 643%of that at room temperature,and the sensitivity of CNTs/BMI-3 at bending can reach 480%of that at room temperature.1000 fatigue tests at room temperature and 100℃show that CNTs/BMI-3 has good fatigue stability The maximum drift ofΔR/R₀ is only 0.04,and the maximum drift is only 0.2 before and after the cycle at 100℃.In addition,after attaching carbon nanotubes,the shape recovery speed of CNTs/BMI-3 structure is improved,and because of its good conductivity,we can monitor the shape recovery behavior of CNTs/BMI-3 structure with electrical signals,which are continuous and stable during the monitoring process,which is of great significance for the use of materials in the fields of aerospace self-deployment,software robots,material damage monitoring,human motion monitoring,etc.