Comment on ``Method to analyze electromechanical stability of dielectric elastomers" [Appl. Phys. Lett. 91, 061921 (2007)]

The model of Zhao and Suo can be readily generalized to predict the critical breakdown electric field $E_c$ value of elastomers with arbitrary elastic strain energy function. An explicit expression for $E_c$ is presented for elastomeric thin films under biaxial strain and comparisons are made with experimental data using a two term Ogden rubber elasticity model. Simplified results for uniaxial and for equi-biaxial stress provide further insight into the findings of Zhao and Suo.