Preparation And Application Of Elastic Conductive CNT/WPU Composite Fiber

With the in-depth integration of multiple disciplines and the development of science and technology,new products and technologies in various fields continue to emerge,such as portable medical monitoring equipment,flexible robots,electronic skins,wearable electronic devices,electronic textiles,etc.The emergence of these technologies and products is not only a milestone in the integration of disciplines and technological development,but to a certain extent reflects the development trend of miniaturization,flexibility,and wearability of electronic products in the future.Wearable electronic products are an important development trend of electronic products in the future.This paper studies the preparation of elastic conductive fibers,an important basic material for wearable electronic products.In this paper,the wet spinning process is used to prepare elastic conductive carbon nanotube/waterborne polyurethane composite fiber,optimize process parameters,study the influence of process,CNT content and other factors on the performance of composite fiber,and explore the process and application of composite fiber made into textiles.Wearable heating and sensor applications.First,the effects of coagulation bath process parameters,metal ion species,concentration,and ethanol solvent on the forming,conductivity and mechanical properties of waterborne polyurethane(WPU)were studied,and the coagulation mechanism of waterborne polyurethane wet spinning was explored.Metal cations are beneficial to the coagulation and molding of anionic waterborne polyurethane WPU,but because different metal ions have different coagulation effects on WPU,the formability in the coagulation bath has a close relationship with the valence and concentration of metal ions.Metal ions with+1 valence(such as Na⁺)cannot completely coagulate WPU.WPU has the best formability in the Ca²⁺coagulation bath,and the optimal concentration range is 1?3wt%.Since the molecular chain of waterborne polyurethane contains hydroxyl groups,it is easier to dissolve in ethanol.Therefore,changing the content of ethanol in the coagulation bath solution will directly affect the morphology of the waterborne polyurethane fiber.With the increase of ethanol content,the waterborne polyurethane fiber gradually changed from solid to porous structure,and the increase of ethanol content significantly improved the mechanical properties of the fiber.The metal ion in the fixed coagulation bath was 1.5wt%calcium chloride.When the solvent was changed from deionized water to a mixed solution of 75wt%ethanol and 25wt%deionized water,the breaking strength of the water-based polyurethane increased from 29.7MPa to37.5 MPa,and the elongation at break increased from 569.1 to 613.7%.Secondly,the effect of carbon nanotubes(CNT)as a filler on the mechanical properties and electrical conductivity of CNT/WPU composite fibers was studied.The resistivity?of CNT/WPU fiber,CNT/WPU film formed by natural drying and CNT/WPU film formed by coagulation bath is compared.When the CNT content is low,the resistivity?of the three has the following relationship:?(coagulation bath Forming film)<?(natural drying forming film)<?(CNT/WPU composite fiber),and as the CNT content increases,their resistivity gradually approaches.When the CNT content is 25wt%,the coagulation bath forms the film,naturally the resistivities of the dry formed film and composite fiber were 0.53?·cm,0.49?·cm,and 1.58?·cm,respectively.Due to the poor plasticity and toughness of CNT,when its content is high,the deformation cannot be quickly dispersed to the surrounding matrix under stress,so it is easy to cause stress concentration.With the increase of CNT content,the mechanical properties of CNT/WPU composite fiber gradually deteriorate.When the CNT content increases from 5wt%to 25wt%,the elongation at break changes from 432.45%.The reduction was 28.21%,and the loss rate was 93.5%.Heat treatment can improve the conductivity of CNT/WPU composite fibers.When the temperature is higher than the glass transition temperature of the WPU,the CNTs will deflect with the movement of the WPU segments,which promotes the formation of a conductive network and improves the conductivity of the composite fiber.Within a certain range,the decrease in resistance is positively correlated with the temperature and time of the heat treatment.Under the process of holding at 75°C for 5 hours,the resistance reduction rate of 13wt%CNT/WPU composite fiber was78.2%,which significantly reduced the resistance of the composite fiber.Finally,the application of CNT/WPU composite fiber in sensor and electric heating field is explored.Under the cyclic tensile test with 10%strain of the fiber without heat treatment,the resistance change range is about 10%,but as the stretching process progresses,the overall fiber resistance shows a decreasing trend;after heat treatment of the fiber,10%The resistance change rate under strain remains 10%,and it exhibits good stability after 200 stretching cycles.Through the manual knitting process,the CNT/WPU composite fiber and ordinary cotton are blended to prepare a conductive fabric,which can reach a stable heating temperature of 75°C under a safe voltage of 35V.The fabric is U-shaped bending,S-shaped bending,and complex deformation.It can maintain a stable heating temperature(?62?)and even heating.