Tuning the Acid/Base Surface Character of Carbonaceous Materials by Means of Cold Plasma Treatments Pietro Favia,* 1,2 Nicoletta De Vietro, 1 Rosa Di Mundo, 1 Francesco Fracassi, 1,2 Riccardo d’Agostino 1,2 1 Department of Chemistry, University of Bari, Via Orabona 4, 70126 Bari, Italy Fax: 0039 080 5443031; E-mail: favia@chimica.uniba.it 2 Institute of Inorganic Methodologies and Plasmas (IMIP)-CNR, Bari Via Orabona 4, 70126 Bari, Italy Received: September 13, 2005; Revised: December 2, 2005; Accepted: December 6, 2005; DOI: 10.1002/ppap.200500073 Keywords: carbon black; plasma treatment; surface modification; water contact angle (WCA) Introduction Carbon black (CB) is the commonly accepted name for a variety of finely divided carbonaceous powders or granules produced by the partial combustion or thermal decomposi- tion of liquid or gaseous hydrocarbons under controlled conditions. The carbon content of CB usually ranges from 80 to 99%, [1] with oxygen and hydrogen being the most common other elements. The surface area, structure, and composition of CB vary over a wide range depen- ding on the operating conditions of the manufacturing process. CB and related carbonaceous materials are widely utiliz- ed as reinforcing fillers in polymer matrices, as adsorbents and filters in many practical applications, e.g., for gases, vapours and liquids, as supports for catalysts and for many other uses. For many years, CB has been the main inexpensive reinforcing filler in rubber goods. [2] Summary: Carbonaceous materials, in the form of flat gra- phite slabs and carbon black granules, are surface-modified in radio frequency (RF, 13.56 MHz) glow discharges fed with NH 3 /O 2 mixtures at different power values, in order to graft oxygen-containing and/or nitrogen-containing chemical groups. In this way, it is possible to adjust the acid/base character of the material surfaces in a predictable way, as a function of the feed composition and of the power. A plasma reactor equipped with a rotating vacuum chamber and internal glass wings is used to keep the granular materials homogeneously stirred and to modify the surface of both graphite slabs and carbon black granules. The chemical modi- fications have been evaluated using X-ray photoelectron spectroscopy. Water contact angle measurements have been carried out on flat graphite, with water solutions at different pH, in order to study the acid/base character imparted to the functionalized surface. Scanning electron microscopy anal- ysis has been performed to check the effects of plasma treatments on the morphology of the substrates. SEM images of an untreated CB granule (left) and the same granule after 20 min of a O 2 - plasma treatment (right). Plasma Process. Polym. 2006, 3, 66–74 ß 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 66 DOI: 10.1002/ppap.200500073 Full Paper