The mathematical model of the thermodilatometric curve obtained in conditions when the structural relaxation and the viscous flow take place simultaneously is presented. The structural relaxation part of the model is based on the stretched exponential relaxation function, and the relaxation times are expressed as proportional to instantaneous viscosity. Mazurin's approximation is used for the viscosity dependence on the thermodynamic and fictive temperatures. The non-linear regression treatment of experimental data enabling the estimation of relaxation parameters together with the thermal expansion coefficients of glass and metastable liquid is proposed. The method and the computer program are verified on the optical glass commonly used as a secondary viscosity standard.
