Scanning electron microscopy (SEM) was applied to investigate
the surface morphology after degradation of silicone rubbers in
different solutions. Fig 7 displays the SEM images of silicone rubbers
with different hardness before and after exposure to simulated
solution for 30 days. All initial samples have rather smooth surface
and no voids or cracks were observed. After degradation in simulated
solutions, voids appeared on surfaces of all the tested samples.
Furthermore, both the size and number of voids increased
with the decrease in hardness, indicating that stability of silicone
rubbers increased with the increase in hardness. This agrees with
the above discussed variation of elastic modulus for silicone rubbers
exposed to simulated solutions.