Electrically conductive polymer composites based on elastic fiber

Abstract

The possibility of obtaining electrically conductive composites by applying carbon suspensions to fibrous materials by aerosol spraying and screen printing, on printing equipment, which ensures high productivity, is shown. A manufacturing technology has been developed and the electromechanical properties of layered fibrous composites based on knitwear and graphite dispersion designed for the manufacture of strain and stress sensors used in "wearable electronics", robotics and medicine have been investigated. In an experimental study, it is shown that the conductive path, that is, the length of the chains of contacting filler particles decreases with tensile deformation due to the growth of microcracks in the material. The electrical resistance of growing microcracks has much higher values than the resistance of deformable piezoresistive material. Cracks can open and close in various ways during bending, torsion, stretching and compression deformation. The electrical conductivity of fibers and filaments significantly depends on the localization of electrically conductive particles on their surface or in volume. The location of the conductive chains on the surface or in the volume of the filaments determines the dependence of the electrical properties of composites on the state of the environment (composition, temperature, humidity). Preliminary studies of filaments with electrically conductive components of various chemical nature (metals, metal salts, carbon in various allotropic forms) show that changes in temperature and humidity significantly affect the resistivity of the conductive fiber. The paper presents data on the effect of temperature and humidity on the electromechanical properties of elastic fiber composites with graphite. When stretched to 15%, the calibration coefficient GF is reduced by 2 times at 100% humidity. The different influence of air temperature in the range of 100C-700C on the deformation and strain sensitivity during cyclic deformation up to 15% and 30% has been established. The presence of two ranges of deformation sensitivity is due to the difference in the mechanisms of elongation of knitwear due to straightening and stretching of threads. Different deformation and strain sensitivity of composites in the ranges of small and significant strains, at different temperatures and humidity of the air, has been established. The strain sensitivity reaches 130, and the strain sensitivity is 12 MPa -1, which is an order of magnitude higher than the stress sensitivity of known polymer composites with various electrically conductive fillers.