Phenomenological and chemomechanical modeling of the thermomechanical stability of liquid silicone rubbers

In this article, we present the constitutive models taking into account the stability of liquid silicone rubber's. We propose the phenomenological large strain viscoelastic material model and the enhanced chemomechanical model. The phenomenological model is calibrated to the experimental investigations probing the thermomechanical behavior of liquid silicone rubber's, while the chemomechanical model uses kinetic theory, to calculate the changes of mechanical properties in time. The proposed chemomechanical model employs: chemical reaction kinetics, statistical mechanics and microstructural based Bergström-Boyce material model. Viscoelastic material property changes resulting from e.g. the variation of crosslink density are computed using the Arrhenius equation. The material model is validated by comparison with results of compression tests of specimens aged in 125 and 175 °C non-loaded and under stress of 0.48 MPa. We achieve 96% compliance for investigated temperature and pressure range. The good agreement with the experimental data, demonstrates that chemomechanical modeling framework provides a useful tool for the prediction of the stability of liquid silicone rubbers and the lifetime of vibration isolators.