Analysis of Thermal Stability of Morphology in Certain Polymers Using X-ray Scattering

Author(s):

Frederick L Beyer and Randy A Mrozek

Abstract:

In this study, X-ray scattering was combined with in situ heating to at least 200 °C to determine the morphological stability of a series of thermoplastics typically used in high-temperature applications. Poly(phenyl sulfone) (PPSU), poly(ether imide) (PEI), and a proprietary blend based primarily on polycarbonate (PC) showed the best thermal stability. Samples of poly(oxymethylene) (POM), poly(p-phenylene sulfide) (PPS), impact-modified high-temperature nylon, and filled high temperature nylon all exhibited changes in morphology as a function of temperature. POM exhibited strong crystallinity at room temperature and displayed a sharp melting transition around 170 °C, becoming a free-flowing liquid. The small-angle X-ray scattering data indicate that the POM crystallites begin to change as early as 130 °C. In contrast, PPS crystallized upon heating, at approximately 105 °C. PPS was found to be morphologically unstable at only 70 °C. The results from this study suggest that PPSU, PEI, and the PC-siloxane product studied here may be considered thermally stable under these testing conditions.