The Applicabilin of Modern Analytical Techniques to Detection of Changes in Roofing Membrane Materials Brought about by Heat Aging

The U,S. Army Construction Engineering Research Laboratories (CERL) has been investigating the development of a test methodology for evaluating the service life of roofing membrane materials. As pat of this effort, CERL conducted a study to investigate the applicability of strain energy (a mechanical test) and Fourier transform infrared (FTIR) spectroscopy (a chemicat analysis) as methods for characterizing changes that rooting membrane materiats may undergo upon exposure to elevated temperatures [1]. In the ease of FTIR, the intent was to evaluate whether changes in the earlxisyl index as a function of therrmd exposure could be used as an indicator of the stability of the membrane materials. The earbonyl index is the ratio of the intensity of the carbonyl absorption band (i.e., C=O) to that of another band (such as C-H stretching or bending) in the spectrum. Increases in a material’s carbonyl index after exposure may bean indkation that oxi&tion occurred during the exposure. Measurements of both strain energy and carbonyl index have been used for specific types of membrane materials. Neither has been applied univerardly to the variety of membrane materials currently available [1].