Effect of temperature on ultrasonic velocity and thermodynamic parameters of bisphenol-C-formaldehyde-acrylate resin solutions

The density, viscosity and ultrasonic velocity (2 MHz) of pure solvents: ethanol, MEK and DMF, and BCFA solutions (0.5–4 wt%) were investigated at three different temperatures: 30, 35 and 40 °C. Various acoustical parameters such as isentropic compressibility (κs), internal pressure (π), free volume (Vf), free path length (Lf) and solvation number (Sn) were determined and correlated with concentration (C). Fairly good to excellent linear relationships are observed at three temperatures. The linear decrease of κs, π and Lf with C and linear increase with temperature; and linear increase of Vf with C and T in DMF system, nonlinear increase with C and T in EtOH system and nonlinear decrease with C and increase with T in MEK system indicated strong molecular interactions in the solutions and solvophilic nature of BCFA, which is further supported by positive values of solvation number. The observed solvation trend is EtOH > MEK > DMF.