Stability of carbon fiber surface functionality at elevated temperatures and its influence on interfacial adhesion

The thermal stability of the surface chemistry of a surface treated carbon fiber, from room temperature to 1000 °C, was investigated by X-ray photoelectron spectroscopy. Within a range of temperatures from room temperature to 400 °C, the only surface functionalities that decomposed were carboxylic acids and dangling nitrogen containing functionalities like amines, amides or nitriles. Significant amounts of water were desorbed as well. This study enabled the testing of the coherence of the fitting of the C(1s), O(1s) and N(1s) peaks. Particularly, when considering the fitting of in the O(1s) peak, carboxylic acids were shown to be included in a single component peak centered at a binding energy of 532.1 eV. The reaction of the carbon fiber surface and an acrylate resin at high temperature, because of the decomposition of carboxylic acids, was highlighted by differential scanning calorimetry. The thermal history of the composite material during its manufacture appeared to be a major influence on the nature of the interactions generated at the fiber–matrix interface and the resulting mechanical properties.