The Adjustment Of Electrically Conductive Network In Conductive Polymer Composites And The Study Of Their Response Behaviors To External Fields

In general,conductive polymer composites(CPCs)are fabricated by incorporating conductive fillers(carbon black,carbon nanotubes,graphene and metal particles,etc.)into polymer matrices.Recently,researches on the structure and property of CPCs have aroused tremendous attention in both industry and academia fields.As a type of functional polymer composites,CPCs not only possess excellent electrically conductive performance and easy processing,but also show a variety of abundant response behaviors when exposed to external stimuli,such as mechanical stress,strain,gases,temperature and humidity.These characteristics provide fodder to explore the microstructure evolution of CPCs,as well as supply theoretical basis for their potential applications in sensing devices.In this paper,based on the design and control of conductive networks of CPCs,we prepared CPCs with different microstructures and explored the response behaviors of CPCs to external stimuli.As a result,a large number of experimental results revealing the relationship between structure and property of CPCs have been obtained.The major results are shown as follows:1.The fabrication and properties of reduced graphene oxide(RGO)/thermoplastic polyurethane(TPU)/polydimethylsiloxane(PDMS)CPCs1)To begin with,aligned TPU fibrous mat was prepared by electrospinning.Then aligned and nonaligned conductive fibrous networks were fabricated by decorating RGO onto the surface of TPU fibrous mat through ultrasonication.Finally,RGO/TPU/PDMS CPCs with a sandwich structure were successfully fabricated by embedding the two conductive RGO/TPU networks into PDMS by a spin coating method respectively.2)Stress-strain and strain sensing behaviors of the two CPCs produced by the aligned and nonaligned conductive RGO/TPU networks were studied.By comparison with the latter,the former exhibited outstanding mechanical strength and responsivity.These differences should be ascribed to the existence of joints and fish scale-likesensing layer on the fibers,which lead to different change of the conductive networks in the process of dynamic tension.3)RGO/TPU/PDMS CPCs fabricated by the aligned conductive fibrous networks showed a broad sensing range(150% strain),high sensitivity(up to 593),excellent cycling stability(>500 cycles),fast response(<160 ms)and benign resistance to humidity and temperature,fulfilling the requirements of remarkable strain sensors.4)The CPCs fabricated by the aligned conductive fibrous networks were assembled onto vigorous parts of body to monitor the motions by the response of the electrical signals,indicating tremendous potential applications in wearable electronics and intelligent robots.2.The fabrication and strain sensing properties of carbon nanotubes(CNTs)/TPU/PDMS CPCs1)First of all,aligned conductive CNTs/TPU fibrous networks was prepared through electrospinning and ultrasonication.CNTs/TPU/PDMS CPCs with a sandwich structure was successfully fabricated by embedding conductive fibrous networks into PDMS by a casting molding method.2)In order to get further information about the microstructure development of the CPCs in tension,the effects of strain amplitude and strain rate on the strain sensing behavior were explored.Large strain amplitude induced a high sensitivity.A higher strain rate generated higher responsivity because the CPCs underwent a large stress,giving rise to more destruction of conductive networks.3)We demonstrated the promise of CPCs in monitoring human motions.The present work provided a new alternative for the manufacture of flexible wearable strain sensors.3.The preparation and temperature sensing behaviors of CNTs/polypropylene(PP)CPCs1)PP with different particles sizes were acquired by dissolving-smashing and direct-smashing method.CNTs/PP CPCs with segregated conductive networks were obtained through mechanical mixing and compression mold.This structure prompted a lower percolation threshold.2)Electrically conductive CNTs/PP composites possessing tunable positive temperature coefficient(PTC)characteristics have been successfully prepared by controlling the size of polymer matrix particles.The percolation thresholds of the three composites decreased obviously with increasing the diameter of PP particles,showing an inverse correlation effect.CNTs/PP CPCs with an extremely high PTC intensity has also been harvested.3)This material can meet new potential demands in tunable temperature sensors.