(489a) A Molecularly Based Method for Predicting the Bulk Properties of Petroleum-Derived Pitches

Petroleum-derived pitch is being investigated as an inexpensive material for carbon–carbon composites. However, a significant drawback of these pitches is their heterogeneity, depending on the initial crude-oil source and the specific method of pitch synthesis. Therefore, today pitches are typically categorized by descriptors limited to bulk properties, including softening point, char yield, and mesophase content. These descriptors do give useful information about each pitch, but prediction of fiber and composite performance from these pitch properties remains elusive.

In this research, a molecular-based method encompassing High-Temperature, Size-Exclusion Chromatography (SEC), Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI), and Supercritical Extraction/Fractionation (SCEF) is proposed. Our ultimate objective is the development of a quick and efficient method to predict downstream material properties of petroleum-pitch-based, carbon–carbon composites.

The first step in this method is the generation of SEC chromatograms for a number of individual pitches. Next, deconvolution of the SEC peaks from each chromatogram is performed, guided by both absolute molecular weight information via MALDI and by unique pitch calibration standards synthesized at Clemson. This deconvolution enables the prediction of the molecular weight distribution and pseudo-component composition for each pitch. Finally, physical deconvolution of the pitches via SCEF will be used to assess and validate the classic, math-based deconvolution method described above.

Successful completion of the above program will facilitate the development of a correlation between the bulk properties of pitches and the molecular weight distribution of the starting pitches. If successful, this research effort would provide us with the tools for “designing” the appropriate molecular composition of a pitch for a given product application.