INTERFACIAL-TENSION BETWEEN POLYMER MELTS MEASURED BY SHEAR OSCILLATIONS OF THEIR BLENDS

When shear oscillations are performed with melts of polystyrene (PS)/poly(methylmethacrylate) (PMMA) blends the total deformation has a large elastic portion at low frequencies. This finding is caused by the interfacial tension acting between the two phases of the blends. A simple model allows one to describe the influence of the interfacial tension on the storage and the loss moduli in a broad frequency range for all mixing ratios of the blend components. The weighted relaxation spectra tau-H(tau) of such blends show an additional peak with a characteristic relaxation time that is correlated with the interfacial tension. From this characteristic relaxation time the interfacial tension alpha between the melts of PS and PMMA can be determined. The resulting alpha = (1.9+/-0.3) x 10(-3) N/m at 170-degrees-C is in good agreement with the value obtained from recovery following melt elongation of the blends.