The Mullins effect is a phenomenon observed in rubber materials where the equilibrium stress-strain response softens with strain history (visco-elastic softening effect).
In contrast to the Payne effect, the Mullins effect can occur in filled and unfilled rubber materials.
The Mullins effect is a particular aspect of the mechanical response in filled rubbers, in which the stress-strain depends on the maximum load previously encountered. It is an instantaneous softening process, which is irreversible.
The Mullins effect occurs whenever the load increases beyond its prior all-time maximum value.
The Mullins effect can be measured with the NETZSCH DMA GABO EPLEXOR®.
The figure below depicts rubbers with fillers. The Mullins effect causes the macromolecular chains to deteriorate and the filler particles to separate from each other destroying the elastomer.