Factors affecting the adsorption of stabilisers on to carbon black (flow micro-calorimetry and FTIR studies) - Part I - Primary phenolic antioxidants

The surface activity of different types of carbon black with phenolic antio xidants is examined using flow micro-calorimetry (FMC), X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared spectroscopy (FTIR). Sig nificant differences in both the overall adsorption activity and the levels of probe adsorption are observed. Differences in behaviour between types o f carbon black are evident and show that the specific surface area is not t he most important factor affecting the adsorption activity, but also the ch emical nature of its surface. Essentially, two factors were found to affect the behaviour of phenolic stabilisers: Phenolic hydroxyl and ester groups were found to form the strongest interactions with carbon black. Furthermor e, steric hinderance of phenolic hydroxyls by alkyl groups is the main fact or which influences adsorption activity. In order to characterise different carbon blacks, FTIR and XPS analysis have been used in an attempt to deter mine the nature of functional groups present on the surface of the carbon b lacks. FTIR analysis also shows that some adsorbed antioxidants on the surf ace of the carbon black could be successfully detected. This provides valua ble information regarding the adsorption mechanisms on to carbon black surf aces. Other techniques included thermogravimetric analysis (TGA), N-2 BET a dsorption studies and Karl Fisher analysis. The latter were performed in or der to determine differences in the volatile and water contents, respective ly, of the carbon black samples. (C) 2001 Kluwer Academic Publishers.