Research On Impedance Property Of Pressure-Sensitive Component Based On Conductive Polymer Composite

As a class of new functional material,Conductive polymer composite has important value in theoretical research and broad application prospects.Carbon nanotubes which are one-dimensioned nano materials have excellent conductivity and great length to diameter ratio.Polymer filled with a handful of carbon nanotubes can form excellent conductive polymer composite.For its good flexibility and fine piezoresistive effect,conductive polymer composite can be the sensitive material of flexible pressure sensor.The substrate material of conductive polymer composite has viscoelasticity and its pressure impedance effect is time dependent,which will influence the precision of sensor seriously.Therefore it is necessary to quantitatively do research on this material time dependment of the stress impedance effect.Aiming to get the quantitative relation between stress and impedance of conductive polymer composite.The advantage of this research is that the flexibility of the sensor will not be influenced.The main contents of this thesis can be outlined as follows:(1)Flexible pressure-sensitive component was made with multi-walled carbon nanotubes for conducting filler,silicone subber for matrix materials,by using co-solution method,assisting with ultrasonic wave and stirring dispersion treatment.The "sandwich" type composite was designed and prepared,which made by using silicone rubber filled with carbon nanotube(mass ratio is 0.001:1,0.002:1,0.005:1,0.008:1,0.01:1 and 0.02:1);(2)The compression stress relaxation experiment of conductive polymer composite based on rubber filled with carbon nanotubes was performed(constant strain of initial stress:0.2MPa-0.4MPa,loading speed:0.3mm/min?5mm/min),obtaining the data of impedance,capacitance,stress and srain varying with the time;(3)The conductive polymer composite's impedance and stress variation relation with time were quantitatively analyzed and the good fitting equations were got.The data of polymer composite 's dielectric constant influenced by AC signal frequency was got and analyzed.(4)According to the relation between impedance modulus and stress,compression stress relaxation monitoring system based on rubber filled with carbon nanotubes is designed,including pressure-sensitive component amplification circuit,data acquisition circuit and relevant PC interface.(5)The relationship between composite material internal structure and the macroscopic electric properties were qualitatively analyzed during compression stress process.The relevant factor to take influence on rubber filled with carbon nanotubes on the number of conductive destruction and restruction channels was qualitatively analyzed.Based on the relation between impedance modulus and stress,the good mathematical fitting equation were found out and the compression stress relaxation monitoring system were designed and its error was less than 12%(range:0-0.4MPa).