Factors affecting the adsorption of stabilisers on to carbon black (flow micro-calorimetry studies) Part III Surface activity study using acid/base model probes

The first and second part of this series of papers investigated the interaction between carbon black and stabilisers (phenolic antioxidants and HALS, respectively) and showed that the mechanism was dependent on both the chemical nature of the carbon black surface and the molecular structure of stabilisers. In this third part, the interactions between model compounds, of varying acidity, and the same four carbon blacks, are investigated using flow micro-calorimetry (FMC) and Fourier transform Infrared spectroscopy (FTIR). As with the first and second parts, differences in adsorption behaviour between the four types of carbon black were evident and were principally related to the chemical nature of the surfaces and the adsorbates. In this study further insight in to the nature of the interactions between the carbon black surface functional groups and the acidic and basic probes has been acquired. The main forms of interaction are hydrogen bonding and Lewis and Bronsted acid/base interactions, formation of proton transfer complexes was also considered possible in cases of strong adsorption. The adsorption behaviour of acid and basic aromatic probes, together with octadecanol and stearic acid, was also found to be dependant on the carbon black surface topography. Flat graphene layers containing minimal heteroatoms favoured adsorption of the latter species as flat adsorption and/or structural ordering was permissable.