AVS 47th International Symposium
    Material Characterization Tuesday Sessions
       Session MC-TuM

Paper MC-TuM5
Thermal Degradation of IM7/BMI5260 Composite Materials: Characterization by X-ray Photoelectron Spectroscopy

Tuesday, October 3, 2000, 9:40 am, Room 207

Session: Real World Surface Analysis
Presenter: S. Ohno, University of Washington
Authors: S. Ohno, University of Washington
M.-H. Lee, University of Washington
K.Y. Lin, University of Washington
F.S. Ohuchi, University of Washington
Correspondent: Click to Email
High performance polymeric composites (IM7/BMI5260) are being considered for use in structures for high speed aerospace vehicles. In this application, composite components are exposed to elevated temperatures for a long time period. This results in physical and chemical degradation of the polymers. In this paper, experimental studies were conducted to investigate the effects of isothermal aging of the IM7/BMI5260 exposed at 150 - 200°C using x-ray photoelectron spectroscopy (XPS). During the XPS measurements, binding energies for the carbon-fibers are uniquely determined because of their electrically conducting nature, whereas binding energies for the polymeric matrix are shifted by the amount of bias voltage applied to an electron flood gun. This effect turns out to be useful to separate out the contribution from carbon fibers and polymeric matrix, thus we have established a unique experimental protocol to analyze the composite material surfaces. Experimentally, the composite specimens were oxidized in an environmental cell specially designed to mimic the aging conditions, and analyzed to learn intrinsic nature of the chemical reactions. These data were further compared with those obtained from long-aged specimen (7 months at 205 °C in air). Our results indicate that degradation of the IM7/BMI5260 is initiated by preferential oxidation of the carbon sites in the BMI to form the carbonyl species, followed by the oxidation to CO@sub2@ leading to degradation.