Reinforcement of model filled elastomers: experimental and theoretical approach of swelling properties

The swelling properties of model filled elastomers consisting of crosslinked polyethylacrylate chains mixed with grafted silica nanoparticles are analysed using a continuous media mechanics approach. We show that the swelling restriction observed in these filled elastomers cannot be simply explained through the increase of the topological constraints density resulting from the interactions at the interface between the particles and the polymer chains. Strong interactions at the particle/matrix interface lead to geometrical constraints which control and restrict the swelling of the polymer network. We propose a model giving an analytical relation between the swelling properties of the filled elastomer, one of the elastomer without particles, and the volume fraction of solid particles. This model describes relatively well the experimental data obtained for varying topological constraint density at the particle surface.