DOWE NEED VERY STIFF FILLERS?

The influence of reinforcing fillers on the stretching of a rubber matrix is analyzed. It is shown that a filler stiffness higher than a critical stiffness does not further enhance the stiffness of the reinforced elastomer. The stiffer filler induces a higher stress-strain concentration and causes filler-rubber dissociation or chain scission at a lower macroscopic strain. Reducing filler stiffness can reduce the stress-strain concentration and therefore delay rubber chain scission or dissociation from the filler surface. Accordingly, the toughness of the reinforced elastomer could be improved. Asimple material model is developed to predict the maximum macroscopic strain without bond scission in a reinforced elastomer. It is shown that reduced filler stiffness is beneficial for cases with (i) reduced bond strength, (ii) increased rubber matrix stiffness, and (iii) increased application strain of the reinforced elastomer. The model can be used to design the appropriate filler stiffness to balance trade-offs of stiffness and toughness of reinforced elastomers.