The use of microwave and FTIR spectroscopy for the characterisation of carbon blacks modified with stabilisers

Abstract

Previous work concerning the overall adsorption activity of different stabilisers [primary and secondary antioxidants and hindered amine light stabilisers (HALS) [Peña, JM, Allen, NS, Edge, M, Liauw, CM. Factors influencing the adsorption of stabilisers onto carbon black: flow microcalorimetry studies J Vinyl Add Technol, 2000;6:62–68] [1] onto carbon black has allowed an understanding of the concentration of stabilisers adsorbed after adsorption and desorption processes. In order to assess directly the amounts of stabilisers adsorbed and desorbed onto the carbon black after the modification, for plastic formulations purposes, microwave dielectric spectroscopy was examined as a potential analytical method, because it is a fast, simple and non-destructive technique. Several carbon blacks (CBs) were modified by adsorption with HALS, primary and secondary antioxidants. UV spectroscopy was used to estimate the CB stabiliser content during modification by assessing the stabiliser concentrations in solution before and after desorption. In addition, the CBs were characterised by X-ray photoelectron spectroscopy (XPS) and FTIR to determine the nature of functional groups on which the adsorption process relies. FTIR was used to study the way in which the stabilisers are adsorbed. Other techniques like thermogravimetric analyses (TGA) were performed in order to estimate the differences in water, volatile content and the amount of adsorbed additive of the CBs. These data were compared with the amounts of stabiliser calculated by flow microcalorimetry (FMC). The results gave several linear microwave calibration plots of the content of adsorbed stabilisers onto the CBs.