Factors affecting the adsorption of stabilisers on to carbon black (flow micro-calorimetry studies) Part II Hindered amine light stabilisers (HALS)

The interaction of hindered piperidine light stabilisers (HALS) with carbon black has been examined using flow micro-calorimetry (FMC) and Fourier transform infrared spectroscopy (FTIR). Significant differences in both the overall adsorption activity and molar heats of probe adsorption are observed. Differences in adsorption behaviour between different types of carbon black were clearly evident and, as with a previous paper (see reference 1, in the latter paper, surface chemistry of the carbon blacks investigated is extensively analysed by XPS, FTIR, N₂ BET adsorption and Karl–Fischer analysis), were mainly to be due to differences in carbon black surface chemistry. The specific surface area merely physically affected the level and heat of adsorption (per unit mass of carbon black). Variation in the degree of substitution of the piperidine amine is an important factor that is found to influence the adsorption activity of HALS, as well as the number of adsorption active and sterically accessible functional groups per HALS molecule. In some cases the adsorbed HALS could be detected by FTIR; shifts in absorption frequencies associated with both the adsorbate and the substrate yielded significant insight into the mode of adsorption of several of the HALS investigated.