Thermostimulated current characterization of poly(ethersulfone)

Two thermal analysis techniques, differential scanning calorimetry (DSC) an d thermostimulated currents, are used to characterize two Poly(ethersulfone s) (PESs) obtained with the same process by two different manufacturers. Th e glass transition temperature observed by DSC is the same for both PESs an d equal to 235 degrees C. When PES samples are heated above the glass trans ition temperature (250-260 degrees C), one initially white and opaque PES ( B) looks transparent while the other one (A) stays in the initial stage. Th e PES B is visibly degraded upon increasing at a lower temperature than PES A. Below the glass transition temperature, two complex relaxation modes al pha and beta situated at +170-175 and -120 degrees C, respectively, are obs erved. The analysis of the fine structure shows that they are constituted o f elementary processes characterized by relaxation times following compensa tion laws. For PES A at high temperatures the cooperative movements are pre cursors of the glass transition. For PES B a double compensation phenomena reveals the biphasic character of the vitreous phase. The comparison betwee n the two PESs reveals different microstructures that could be due to diffe rent processing conditions. (C) 2000 John Wiley & Sons, Inc.