A highly convergent algorithm for phase equilibria calculations of ternarypolymer/solvent systems using an equal-area rule method

Solubility diagrams of ternary polymer systems are usually analyzed using c alculated critical points and spinodals rather than tie lines and binodals. This is partly because achieving convergence in rigorous calculations of t ie Lines and binodals is difficult. To overcome this problem, we have exten ded the equal-area rule (EAR) method for calculating phase equilibria of sy stems containing small molecules to calculate the tie lines and binodals of polymer 1/polymer 2/solvent and polymer/solvent 1/solvent 2 systems. An ad vantage of the EAR method over those available in the literature for calcul ating the tie lines and binodals is that this method does not require an in itial guess for the equilibrium concentrations to begin the calculation pro cess. This capability is particularly useful for prediction purposes in the absence of experimental data. The method has been applied to several polym er/solvent ternary systems using the Flory-Huggins model to represent the c hemical potentials of the components. The results show that the EAR method is highly efficient and reliable in calculating the tie lines and binodals in ternary polymer/solvent; systems.