Preparation And Properties Of Elastic Polyurethane-based Conductive Fibers

In recent years,with the rapid development of intelligent technology,people’s demand for intelligent wearable devices is increasing day by day.In order to meet the multi-functional needs of human body and the integration of clothing,traditional rigid intelligent wearable devices are gradually transitioning to flexible and stretchable intelligent textiles.As the basic component of flexible intelligent textile,conductive fibers should have excellent electrical conductivity and stretchability to meet the electrical performance requirements under different deformation.Traditional metal conductive fibers have poor stretchability and flexibility when applied to fabrics.The hybrid technology combining conductive nano materials with polymers is an effective method to improve the elasticity of conductive fibers.However,the dispersion of conductive nano fillers in the spinning solution and fiber matrix often brings great challenges to the spinning process and fiber properties.In this paper,using thermoplastic polyurethane（TPU）as the elastic matrix and introducing soluble silver trifluoroacetate（C₂Ag F₃O₂）as the precursor of silver nanoparticles（Ag NPs）in the spinning solution,Ag NPs/TPU elastic conductive fibers were prepared by wet spinning and in-situ reduction techniques.On this basis,silver nanowires（Ag NWs）@Ag NPs/TPU spiral conductive fibers were prepared by means of twisting and surface imprednation.The unique structural significantly improved the electrical response range and tensile resistance stability of polyurethane based elastic conductive fibers during the tensile process.The main research contents were as follows:The Ag NPs/TPU elastic conductive fibers were prepared by wet spinning and in situ reduction process,and the effects of different preparation conditions on the conductivity,morphology and chemical composition of the fibers were investigated.When the mass ratio of C₂Ag F₃O₂/TPU was 1:1,the concentration of L-ascorbic acid was 2.5 wt%,the reduction was carried out at 60℃for 1 h,the Ag NPs/TPU elastic conductive fiber with complete Ag NPs conductive layer was obtain,and its conductivity upped to 1772 S/cm.Furthermore,the effects of silver precursor content and reduction temperature on the properties of Ag NPs/TPU elastic conductive fibers were investigated.The results showed that the relative resistance change（ΔR/R₀）of fibers firstly decreased and then increased with the increase of C₂Ag F₃O₂content in the same strain range.With the rising of reduction temperature,the resistance stability of fibers increased.Ag NPs/TPU elastic conductive fiber not only retained the high stretchability of TPU fiber,but also had high conductivity,efficient electricity-heat conversion,and repeatability under low strain.The application of Ag NPs/TPU elastic conductive fibers in stretchable wire,electrical heating fabric and intelligent sensing had been proved.In order to improve the electrical stability of elastic conductive fibers under large strain,Ag NPs/TPU spiral conductive fibers with spring-like structure were prepared by fiber twisting on the basis of the preparation process of Ag NPs/TPU elastic conductive fibers.Their electrical response range could reach 300%,which was twice that of untwisted fibers.At the same time,theΔR/R₀of Ag NPs/TPU spiral conductive fibers was only 0.98 under 100%tensile strain,and exhibited excellent cycling stability under 500 times of 50%strain.Ag NPs/TPU elastic conductive fibers were impregnated with Ag NWs in a pre-strain state to improve the initial conductivity of the fibers,and the resistance of Ag NWs@Ag NPs/TPU spiral conductive fibers was reduced by80%after impregnation.At the same time,the Ag NWs@Ag NPs/TPU spiral conductive fibers maintained superior resistance stability under different tensile strains and different tensile speeds,and showed long-term stability in the process of 1500 cycles under 50%strain,showing great potential in stretchable wire applications.