Thermodynamic model and surface tension analysis of borosilicate glasses for pharmaceutical applications

The surface tension of 17 borosilicate glasses representative of pharmaceutical applications was determined at 1190 °C using the sessile drop method. The measured values ranged from 285 to 333 mN m −1 and showed a clear dependence on glass composition, with increasing alkali modifier content generally associated with lower surface tension. The Shakhmatkin–Vedishcheva thermodynamic model (SVTDM) was used to describe the equilibrium distribution of structural components in the melts and to establish a relationship between melt structure and surface tension. Multilinear regression identified B, BaS2, C2BS, and NB3 as surface active components associated with lower surface tension. These results indicate that surface tension in multicomponent borosilicate melts is related to the equilibrium distribution of structural components rather than to individual oxide concentrations, providing a thermodynamic link between melt structure and surface properties.