A model to explain the decrease of the dynamic storage modulus of carbon black filled elastomers with increasing deformation amplitude is presented. The model of the variable network density gives a molecular interpretation of the behaviour of storage and loss modulus. Contrary to the structure breakdown model of carbon black the new model explains the effect by interactions between filler and polymer. It is based on an adsorption mechanism of network chains on the surface of the filler particles. The calculated activation energy of desorption is within the range of van der Waals interaction.