Stress induced cracks in carbon black filled elastomers probed by atomic force microscopy

In the current study, carbon black (CB) filled ethylene butylacrylate copolymer samples, which are submitted to a uniaxial creep, are probed with a sub-100-nm spatial resolution using atomic force microscopy in tapping mode. We demonstrate the significant effect of the long-time application of stress, at low strain amplitude well below the breaking threshold, on the crack occurrence along the interfaces between polymer and CB aggregates. The data analysis indicates a log-normal distribution of crack width whose average value follows an exponential saturation as a function of aging time. A possible model realizing this behavior is the rate dependent theory of fracture for polymers.