Miscible PS/PPE compounds: an alternative for blend phase morphology studies? Influence of the PPE content on the surface tension of PS/PPE and on the interfacial tension in PP/(PS/PPE) and POM/(PS/PPE) blends

The influence of the PPE content in a miscible PS/PPE phase on the surface tension and polarity of PS/PPE mixtures, and on the interfacial tension in PP/(PS/PPE) and POM/(PS/PPE) blend systems was investigated. Surface tensions, sigma(T), and polarity, x(p), were experimentally determined by means of the pendant drop analysis technique, and were compared to the values predicted theoretically via Macleod's theory. The interfacial tension, sigma(12), was determined both from the dynamic breaking thread method, and from the pendant drop analysis, which is an equilibrium method. The experimental values were compared to those predicted from the harmonic mean equation. Good agreement was found between the absolute values for sigma(12) Obtained from both the techniques. The surface tension of the PS/PPE mixtures, in a temperature range of 230-260 degrees C, appears to be unaffected by the presence of PPE, within the experimental error of the measurements. These findings were in good agreement with the prediction of a(T) from Macleod's theory. The interfacial tension of the PP/(PS/PPE) or POM/(PS/PPE) blend systems did not seem to be affected significantly when using a PS/PPE phase with a higher content of PPE. Finally, calculations showed that PPE causes the polarity of the PS/PPE mixtures to increase slightly from a value of 0.17 for pure PS to 0.20 for pure PPE. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.