A refined approach to bubble nucleation is presented and applied to polymer foaming process, The integral overall energy balance and the integral Clausius-Duhem inequality are used to analyze a bubble nucleation experiment. The computation of long-range intermolecular potential results in expressions for surface tension, work, and critical work for cluster formation, as functions of the Hamaker constant, molecular and/or repeat unit interaction distance, molar fractions of each component, and cluster radius, The variation of surface tension with cluster size, temperature, and pressure is determined in terms of well-known macroscopic properties and compared with available experimental data.