Pressure and temperature dependence of viscoelastic properties of polymethylphenylsiloxane fluids

Abstract

Measurements have been made of the viscosity, density and shear mechanical resistance for two polymethylphenylsiloxane fluids. Results show that the high frequency limiting compliance J_∞ increases linearly with temperature and G_∞(= 1/J_∞) increases linearly with pressure as for non-polymeric liquids. Data obtained in the relaxation region by variation of pressure and temperature are described in terms of the complex compliance, J*(jω)=J_∞(1 + 1/jωτ_m)+FJ_∞/(jωτ_m)^β, which is the high frequency approximation to the expression J*(jω)=J_∞(1 + 1/jωτ_m)+J_r/(1 + jωτ_r)^β. Here τ_m is the ‘Maxwell relaxation time’(=ηJ_∞), J_r is retardational compliance and τ_r is the retardation time.