The Study Of Mechanical And Electrical Properties Of Epoxy Coating CNT Yarn Composites

CNT yarns as a new flexible electrical material possessed with piezoresistivity and sensing property have a wide range of applications in many fields.However,the aerogel-spun CNT yarns with loose and porous structure perform less desirable mechanical properties resulted from the weak der Waals forces between CNTs and CNT bundles,making it hard to satisfy the requirements of practical applications.To solve the problems mentioned above,in this study,the CNT yarns are modified by physical method,coated by Epoxy and reinforced by adding NH₂functionalized CNT?N-CNT?particles,detailed information is shown as follow s:Firstly,the internal structure and mechanical properties of CNT yarns are modified by cryogenic treatment with acetone?-196?,nitrogen?.The tensile strength of the CNT yarns is156.64MPa,improved by 24.78%after cryogenic treatment with acetone and recovered at room temperature?13??,compared with the tensile strength of pristine yarns 125.54MPa due to the increase in size of the internal CNT bundles of treated CNT yarns;The Young's modulus of the treated CNT yarns are 5.23GPa,increased by 30.75%compared with the 4GPa of the pristine yarns,the breaking elongation of the treated CNT yarns has no big difference compared with the pristine yarn,as well the electrical conductivity.It can be concluded that the way of cryogenic treatment in acetone which is simple,easy to be implement ed without pollution,could be a novel and effective way to improve the structure and mechanical properties of CNT yarns.Secondly,CNT yarns are coated by various concentrations of Epoxy solutions to further improve the mechanical properties,the electrical properties and strain sensing properties of the CNT yarns are compared and analyzed.Compare with the pristine CNT yarns,the CNT/Epoxy coating yarns prepared by 90 percent of Epoxy?Epoxy/Acetone?possess a tensile strength of308.78MPa,increased by to 146.4%,Young's modulus is 12.5GPa,increased by 157.3%,the breaking elongation is decreased by 28.67%,the electrical conductivity is decreas ed by 28.67%;the CNT/Epoxy coating yarns possess a special high sensitivity in 2%strain.The CNT/90%Epoxy coating yarns show the sensitivity of 9.72 in 2%strain,demonstrating its potential use for sensing applications.Moreover,to further improve the mechanical and electrical properties of CNT/Epoxy coating yarns,the NH₂ functionalized CNT?N-CNT?particles are added in the Epoxy solutions to modify the brittleness and improve the affinity of the Epoxy with the CNT yarns.The dispersions of N-CNT in four kinds of solvents and the solutions of solvents and Epoxy are compared and analyzed,then the CNT/Epoxy coating yarns added 0.1%N-CNT?N-CNT/Epoxy?dispersed by different solvents with the same concentration of 20%?solvent/Epoxy?are prepared and the mechanical,electrical and strain sensing properties are analyzed,among all these prepared coating CNT yarns,20%Ethanol/0.1%N-CNT/Epoxy coating CNT yarns show the best mechanical and electrical properties,the strength and modulus are 431.32MPa,13.32MPa,increased by 243.57%and 233%,compared with pristine yarns,respectively.The electrical conductivity is almost the same with the pristine yarns and the gage factor 2?over 2%strain?are improved by 44.06%compared with pristine yarns.Lastly,the CNT/Epoxy coating yarns added different concentration?0.05%,0.1%,0.2%?of N-CNT dispersed by 20%Ethanol are prepared.20%Ethanol/0.1%N-CNT/Epoxy coating CNT yarns show the best mechanical and electrical properties,compared with 20%Ethanol/Epoxy coating CNT yarns,the tensile strength and Young's modulus are increased by 45%and 39%,respectively,the breaking elongation are decreased by 34%;The electrical conductivity is665.49S/cm,increased by 105.8%,the resistance is decreased by 44.17%,gage factor 1?in 2%strain?and gage factor2 are increased by 37.16%,80.7%,compared with 20%Ethanol/Epoxy coating CNT yarns,respectively.In conclusion,20%Ethanol/0.1%N-CNT/Epoxy coating CNT yarns possess the optimal mechanical and electrical properties demonstrating its better application in the future.