Preparation Of Carbon Nanotube/Waterborne Polyurethane Coated Conductive Yarn And Its Performance And Application Research

Carbon nanotubes have received more and more attention from researchers in the preparation of conductive yarns and their applications due to their excellent electrical and thermal conductivity and mechanical properties.Conductive yarns prepared based on carbon nanotube coating can integrate carbon nanotubes on yarn materials and can be prepared for different structural levels of electrical functional smart textile applications.The conductive yarn prepared by the coating method is simple in preparation and low in production cost,and through the selection and optimization of yarn structure can reduce the use of conductive materials to achieve a significant increase in yarn conductivity,while reducing the cost of yarn preparation and yarn performance can be guaranteed or even improved,however,it is difficult for CNT-coated conductive yarns to have good mechanical and conductive properties at the same time due to the agglomeration of CNT,the fluffy structure of cotton yarn but poor mechanical properties,the high strength of chemical fiber but the tight structure,and the poor bonding with carbon nanotube interface.To solve these problems,carbon nanotubes/waterborne polyurethane(CNTs/WPU)composite conductive ink was prepared by using carbon nanotubes as conductive material and environmentally friendly waterborne polyurethane as adhesive.The fluffy and porous polyester false twist low elastic yarn(DTY)was used as the yarn matrix to form the isolation structure of the inner/outer coating,and the performance of the coated conductive yarn was improved by dipping-stretching heat setting process,and the carbon nanotubes/WPU with high conductivity was prepared.Then,the surface morphology,internal structure,conductivity,mechanics,sensing,electrical stability,electric heating,and other properties were studied,and it was applied to the field of intelligent textiles,which verified its application potential in the field of intelligent textiles.Firstly,different systems of PU(polyurethane)-CNTs/WPU composite conductive were prepared,and its surface morphology,viscosity,conductivity,and other properties were analyzed,as well as the basic parameters of DTY,and the conductivity and yarn structure were analyzed using different systems of PU-CNTs/WPU single coating DTY,to determine the CNTs/WPU preparation system.The results show that the apparent viscosity of conductive ink increases WPU,but the more PU content,the less ink conductivity decreases.2%wt PU-CNTs/WPU composite conductive ink has the most suitable viscosity and conductive properties,can completely penetrate the pores and adhere to the yarn,filling the pores and obtaining a high conductivity.Secondly,using 2% WPU-CNTs/WPU,the yarns were dipped and coated several times by "dipping-drying","dipping-twisting-drying" and "dipping-stretching heat-setting" processes.DTY,CNTs/WPU coated conductive yarns with different structures were prepared:CNTs/WPU-DTY(CWY),Twisting-CNTs/WPU-DTY(TCWY),and Stretching-CNTs/WPU-DTY(SCWY),and their surface morphology,internal structure and conductive,properties were characterized and analyzed.The results showed that the yarns all formed an isolated structure with internal/external coating and obtained higher carbon nanotube loading and conductivity compared with other carbon nanotube-coated conductive yarns in the literature,and SCWY straightened the internal monofilaments of the yarns by stretching to form a better conductive pathway with the highest conductivity.Thirdly,the mechanical,sensing and electrical property changes of CNTs/WPU coated conductive yarns under cyclic stretching and bending processes were characterized and analyzed using a single fiber strength stretching instrument and a digital multimeter.The results show that twisting and stretching make the yarn obtain a tighter structure,TCWY and SCWY have a greater increase in breaking strength and breaking elongation compared with CWY,and the internal monofilaments of SCWY are completely straightened and not easily deformed when subjected to stretching,obtaining a higher sensing sensitivity and sensing coefficient.In addition,the internal and external coatings of SCWY are subjected to the same force under the effect of cyclic deformation,and there is no stress concentration.Meanwhile,the shrinking effect of PU curing makes the interaction between carbon nanotube filaments stronger,and excellent electrical stability is obtained.Finally,the electrothermal performance of SCWY under different applied voltages with variable voltage and electrothermal stability under the same voltage cycle was investigated using a far-infrared thermal imaging camera,and its application in the field of smart wear was explored.The results show that the temperature of SCWY can be precisely regulated by voltage,and the temperature response is rapid,with higher electro-thermal conversion efficiency and response speed than those in the same type of literature.And it shows excellent electro-thermal cycle stability with a large number of cycles at different voltages,respectively.In addition,SCWY can be prepared into conductive fabric by sewing,embedding,weaving,etc.The "conductive fabric" prepared by SCWY has a uniform and stable heat generation;the "conductive fabric" is bonded to the hand model to simulate its actual application and still has uniform heat generation The heat generation will not change under the condition of bending and winding.It shows that it has a broader application prospect in the future development of flexible electronic wearable devices and the smart textile industry.