PECULIARITIES OF RELAXATION PROCESSES IN THE MESOPOROUS MATRIX - NEAR-CRITICAL FLUID SYSTEMS IN THE VICINITY OF THE CRITICAL POINT OF THE SATURATING FLUID
The paper presents the results of relaxation dynamics in the «mesoporous matrix - a near-critical fluid» system, when the system occurs between the two thermodynamic equilibrium states characterized for different values of the fluid density. The total field speckle correlometry method is applied to evaluate the volume-averaged values of the porous matrix local strain rate in the transition process. The investigated samples were porous polymeric matrices with the structure based on fibrillar polytetrafluoroethylene and cellulose fibers and saturable transcritical carbon dioxide. Verification of the developed formalism Biot phenomenological model of the porous matrix viscoelastic relaxation was carried out using the analysis of the scaling properties of the local strain rate dependence and relaxation time of the thermodynamic temperature deviation from the critical value. A new method is proposed to evaluate the matrix characteristics (bulk modulus, porosity, average pore size) according to the speckle correlation diagnostic system relaxation.