Factors affecting the adsorption of fatty acids, alcohols and aromatic compounds on to carbon black pigments (flow micro-calorimetry studies)

The surface activity of different types of carbon black with fatty acids, alcohols and aromatic compounds, is examined using flow micro-calorimetry (FMC), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Significant differences in the overall adsorption activity of fatty acids and aromatic compounds are observed. The differences in behaviour between the various types of carbon black are evident and show that the specific surface area, as well as, their chemical nature are integral factors affecting the adsorption activity. Essentially, four factors were found to affect the adsorption activity of the fatty acids and alcohols: the presence of carboxylic and hydroxyl groups (which are found to form the strongest interactions with carbon black), the length and linearity of the hydrocarbon chain and the presence of unsaturation in the structure. Presence of aromatic ring type of functionality and size are also determinant factors in the adsorption of aromatic compounds. In order to characterise different carbon blacks, FTIR and XPS analysis have been used in an attempt to determine the nature of functional groups present on the surface of the carbon blacks. This provides valuable information regarding the adsorption mechanisms onto carbon black surfaces. Other techniques include thermogravimetric analysis (TGA), N2 BET adsorption studies and Karl Fisher analysis. The latter tests were performed in order to determine differences in the volatile and water contents, respectively, of the carbon black samples.