Resistive viscoelasticity of silicone rubber/carbon black composite

Electrical conductive polymer composites are shown as prospective flexible pressure and stretch sensors for detecting the dangerous deformations and for sensing the pressure with minimal intrusion. To better understand the piezoresistive mechanism and improve the performance of this type of sensor, a series of experiments were conducted to investigate the resistive viscoelasticity of silicone rubber/carbon black composite film. First, the flexible conductive composite film was composed with liquid silicone rubber as the matrix and conductive carbon black as the filler. The filler loading was fixed at 5 phr in mass ratio. Then, the resistive viscoelasticity of the composite film was studied as a function of frequency in the range from DC to 1 MHz, including resistive creep, resistive relaxation, and resistive recovery, although in a standard experiment, one-step stress or one-step strain was loaded in transient time and the resistance responses were measured. Result from the experiment shows that the creep of resistance is composed of two distinct segments. One is coincident with the strain creep of a typical viscoelastic material, while the other is quite different. Both the relaxation and the recovery of resistance exhibit strong frequency dependence. The relaxation speed becomes slower with the increase of exciting frequency except DC, and the relaxation speed is marginal when excited by DC electrical field. The recovery time becomes shorter with the increase of the exciting frequency.