Thermal degradation of IM7/BMI5260 composite materials: characterization by X-ray photoelectron spectroscopy

Thermal degradation mechanisms of the graphite/polymeric composite (IM7/BMI5260) have been characterized using X-ray photoelectron spectroscopy (XPS). Binding energies of carbon fibers can be uniquely determined due to their electrically conducting nature, whereas those of the polymeric matrix are shifted by the amount of bias voltage applied to a charge neutralization electron flood gun. This effect turns out to be useful in separating the contribution from carbon-fibers and polymeric matrix, thereby changes associated with photoelectron peaks for carbon-fibers and polymeric matrix can be measured independently. An ‘in-situ’ oxidation chamber was constructed to simulate the environmental conditions. It was found that the thermal degradation was initiated by preferential oxidation of weakly bonded carbons in BMI5260, converting to carbonyl species, followed by the total degradation of polymer backbone structure. No change in the carbon fibers was detected throughout the course of ‘in-situ’ treatment.