Factors affecting the adsorption of stabilisers on to carbon black (flow micro-calorimetry studies) - 4. Secondary antioxidants

The surface activity of different types of carbon black with secondary anti oxidants (aryl phosphites and phosphonites) is examined using flow micro-ca lorimetry (FMC), X-ray photoelectron spectroscopy (XPS) and Fourier transfo rm infra-red spectroscopy (FTIR). Significant differences in both the overa ll adsorption activity and the levels of probe adsorption are observed. Dif ferences in behaviour between types of carbon black are evident and show th at the specific surface area is not the most important factor affecting the adsorption activity, but also the chemical nature of its surface. Essentia lly, two factors were found to affect the behaviour of phosphite stabiliser s: Phosphite and phenyl groups were found to form the strongest interaction s with carbon black. Furthermore, steric hindrance of Phosphite by alkyl gr oups and the three dimensional structure are the main factors, which influe nce adsorption activity. 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 prov ides valuable information regarding the adsorption mechanisms on to carbon black surfaces. Other techniques include thermogravimetric analysis (TGA), N-2 BET adsorption studies and Karl Fisher analysis. The latter tests were performed in order to determine differences in the volatile and water conte nts, respectively, of the carbon black samples. (C) 2001 Elsevier Science L td. All rights reserved.