SMALL-ANGLE X-RAY-SCATTERING (SAXS) IN CARBONIZED PHENOLIC RESINS

Small-Angle X-ray Scattering (SAXS) has been used as an analytical tool to study the development of microstructure with increasing Heat Treatment Temperature (HTT) of a carbonized phenolic resin, which is often used as matrix in commercial carbon-carbon composites. Processing parameters-heating rate and maximum heat treatment temperature-were the primary variables of interest. Results from SAXS have led to the consideration of a model for microstructure development in carbonized phenolic resins. Local density variations on the 10 angstrom-100 angstrom scale seem to be the predominant feature of these carbonized resins in the temperature range studied (450-900-degrees-C). Heat treatment results in a gradual destruction of crosslinks, which leads to clustering of the aromatic units. These clusters enclose pores, the high concentrations of which give rise to scattering maxima in SAXS data. Concentration and dimensions of pores are sensitive both to the heating rate used and the maximum carbonization temperature.