Background: Carbon black - silicon rubber nanocomposites are under consideration for
medical applications involving tremor mitigation as well as general therapeutic applications involving
muscle relaxation therapy.
Method: Carbon black filled silicon rubber composites containing 40-100 phr (per hundred) carbon
black were investigated for their electrical conductivity under different loads over time. Rheological
experiments involving evaluations of the storage moduli, G´ for the composites were also performed
to infer rate and strain dependence of the composites’ conductivity under compressive loads.
Results: Due to the high deformability of silicon rubber, the percolation thresholds for carbon black -
silicon composites were shown to be a function of compressive loads applied on them. Conductivity
of such composites increased with time and compressive load levels applied. The rheological experiments
revealed that strain level and frequency can also indirectly affect the resistivity/conductivity
levels in carbon black -filled silicon rubber composites, with the storage modulus increasing monotonically
with increasing frequency (rate), and the stiffness of the carbon black /silicon rubber composite
decreasing with increasing strain levels. Thus, it becomes easier to compact the nanocomposite
further at higher strain levels and we would expect the rate of decay in resistivity to be lower at higher
rates of pressure application.
Conclusion: Our experimental results reveal that the two important service parameters, strain level
and loading rate can be used for controlling the resistivity/conductivity levels in carbon black-filled
silicon rubber composites.