Preparation And Application Research Of Conductive Composite Yarn Based On Reduced Graphene Oxide

Wearable flexible electronic devices with its good flexibility,comfort,portability has been widely used in sports detection,medical health,intelligent protection and other fields.With the continuous research on wearable flexible electronics,excellent sensing performance,reliable service life and multi-functional integration are necessary for the development of wearable flexible electronics.Polyurethane yarn(PU)has strong tensile properties and expandability as a common textile material,making it an ideal substrate material for the preparation of wearable flexible electronic devices.In this paper,a modified Hummers method was used to prepare graphene oxide(GO)and to modify and dope it.Three kinds of conductive yarns were prepared to study their conductive properties,tensile sensing properties and electro-thermochromic properties.The specific research contents are as follows:The first part of the thesis is the synthesis of graphene oxide by a modified Hummers method,which successfully introduced oxygen-containing functional groups into graphite and prepared state-stable GO dispersions.Water polyurethane was mixed with GO dispersion to prepare reduced graphene oxide composite yarn(r GO-PU)by impregnation method.The effect of water polyurethane addition and weight gain percentage on the electrical conductivity of composite yarn was investigated.The formulation of conductive ink and the preparation process parameters of composite yarn were determined.The electrothermal performance of r GO-PU was investigated,which could warm up 24.8℃ for 10 s at 14 V with a fast thermal response rate.The second part of the paper used glucose as a reducing agent to synthesize composites of silver nanoparticles and reduced graphene oxide(r GO)in one step reduction and configured conductive ink to prepare reduced graphene oxide/silver nanoparticle composite yarns(r GO/Ag-PU).Benefiting from the abundant oxygen-containing functional groups on the GO sheets,the silver nanoparticles can adsorb on the r GO sheets and connect the adjacent r GO sheets to improve the electrical conductivity of the composites(1.25kΩ/cm).On the other hand r GO covered with silver nanoparticles can protect them from oxidation.The prepared composite yarn has a favorable strain response with a sensitivity of 16.44 in the strain range of 107%-275% and good reproducibility.Its electric heating performance has been greatly improved,and it can warm up 28.6℃ at 7V and 56.3℃ in the state of two composite yarns twisted.The third part of the paper prepared reduced graphene oxide/carbon nanotube composite yarns(r GO/CNT-PU).The 1D CNT and 2D r GO form a more channel-rich conductive layer,thus improving the conductivity of the composite yarn(435Ω/cm).At the same time,the doping of CNT creates more contact sites when the composite yarn is stretched-shrunk,exhibiting better strain sensing characteristics with a response range of 400%.With a sensitivity of 7.84 in the 0%-140% strain range,it can detect movements of different amplitudes in the fingers,elbows,etc.Based on the improved electrical conductivity of the composite yarn,its electrical and thermal properties have been further improved.It can warm up to 32°C at 4V,which meets the safety voltage requirements of flexible electronic devices and the color change temperature requirements of thermochromic inks.The transition from orange to yellow,or from brown to red,can be accomplished at a low voltage of 4V,enabling the multi-functionalization of flexible electronic devices.