Application And Development Of Electrothermaland Sensing Textiles Based On Carbon Nanotube Twisited Yarn

With development of time,people require more functions from traditional textile.Due to this,smart textiles have emerged and been paid much more attention.The development of such multifunctional textiles is inseparable from the research of smart materials.As a new generation of materials,carbon nanotubes（CNTs）possess excellent features such as mechanical,sensing,and electrothermal properties etc.However,CNT yarns currently produced have poor abrasion resistance,low breaking strength,and potential cancerous hazard when applied in the textile garments.Therefore,A CNT film twisting process has been introduced for CNT twisted yarn.Then,polyvinyl alcohol（PVA）has been used to infiltrate CNT materials,which provided CNT yarn with high strength and good abrasion resistance.Considering excellent electrothermal and sensing properties of CNT materials,The prepared composite CNT twisted yarn has been integrated with three dimensional spacer structure featuring lightweight,anti-lamination and high strength and braided to form sensing rope.The main conclusions are as followed.Firstly,Different coating processes and PVA solutions have been studied to enhance mechanical properties of composite CNT twisted yarn,in which direct coating of PVA solution infiltrated on the surface of CNT twisted yarn and indirect coating of PVA solution infiltrated on the CNT film and then twisted to be composite CNT yarn have been involved.It is found that when twist amount and film width are maintained at 6 twist/cm and 2 mm respectively,compared with untreated CNT twisted yarn,the composite CNT twisted yarn prepared by indirect coating method has increased tensile strength of 127%from 74MPa to 167MPa and improved abrasion resistance of 900%.In addition,dimethyl sulfoxide（DMSO）is introduced to overcome the water repellent feature of CNT,which acts as a bridging element between PVA polymer and CNT bundles,so mechanical property is further improved.When the amount of twist and film width are matained at 12 twist/cm and 5mm and indirect coating treatment is chosen,The composite CNT twisted yarn treated by PVA&DMSO has increased tensile strength of 23.4%from 526MPa to 650MPa compared to the composite CNT twisted yarn treated by PVA&H₂O.Therefore,With the help of indirect coating treatment and DMSO bridging effect,a composite CNT twisted yarn with high strength,good abrasion resistance and greater flexibility has been fabricated.Secondly,Electrothermal property of composite CNT twisted yarn prepared by indirect coating and PVA&DMSO solution has been studied and its integration with three dimensioanl glass fiber fabrics and woven composite is also explored.The results show that whether CNT twisted yarns are treated by polymer or not,they usually experience heating,stabilizing and cooling processes,with no effect on its fast thermal response characteristic under constant voltage.However,the surface temperature of treated composite CNT twisted yarn is lower than untreated one,reaching 125℃and 200℃respectively at 2.5V,still exhibiting good thermal property.In addition,with step-by-step and cyclic voltage applied,the composite CNT twisted yarns display an excellent thermal stability and durability.When combined with three dimensional weaving technology,followed by curing process with epoxy resin,the composite CNT twisted yarn can generate heat normally through voltage applying as weft,warp and vertical yarns,reaching77.3℃,72℃,43℃ at 6V.The final product has shown a great potential application in industrial field such as electric heating floor.Finally,in order to meet the complex climate of ocean and chemical factors,polyimide（PI）is used to coat on the surface of composite CNT twisted yarn prepared by indirect coating and PVA&DMSO solution.Insulation feature and sensing performance of produced PI based composite CNT twisted yarn have been studied.As for insulation property,Interior resistivity of composite CNT twisted yarn is as normal as the untreated CNT twisted yarn while the outer layer is insulated completely,Resistivity could be as high as 1.21×10⁸Ω·m,which has already broken through the threshold of engineering insulation materials.The sensing property of PI based composite CNT twisted yarn still possess a great advantage,with gauge factor 0.905 and 0.564 for treated and untreated respectively.Although the linearity of sensing property for composite CNT twisted yarn is affected after braiding and embedding,it could still realize transportation of mechanical signal and embedding method to fabricate sensing rope is more reliable and stable than braiding method.