Carbon black functional group characterization

Fourier Transform IR Spectroscopic Characterization of the Functional Groups on Carbon Black... 

Besides water and organic compounds, the evaluation of heats of iimnersion in alcohols has also been emplt ed for the characterization of the surfece chemistiy of carbons [308-311], In this context, the active hydrogen-containing sites of the functional groups, such as hydroxyls or carboxyls, present on carbon blacks were evaluated ftom the heats of inteiactiona between those sites and various alcohols. The immersion heats of the carbon... 

In the 1960s, carbon blacks were mainly prepared by channel processes, and their acidic functions were present at about 10 eq/g, which allows relatively easy determinations but now, with furnace blacks, the surface acidic functions are generally of about 10 eq/g, and specific techniques (Bertrand and Weng, 1998) or drastic reaction conditions must be used (Custodero et al., 1992). Obviously, such delicate determination must be conducted on previously extracted black, in order to eliminate basic mineral impurities that would hinder any characterization of the rare acidic groups present on carbon black. 

Oxygenated Functions. Oxygenated functions on carbon black surface were observed in the early 1950s [70] and completely characterized by H. P. Boehm in the 1960s [71]. At this time, interaction between carbon black and natural rubber was considered the consequence of chemical reactions between the carbon black surface s acidic groups and basic moieties present in the natural rubber structure [71a]. 

The carbon black surface function characterization consists of suspending a given amount of carbon black in solutions of known normality of basis of different strength NaHCOs, Na2C03, NaOH in water, and EtONa in ethanol [72]. Then carbon black is filtered and the number of reacted acidic groups obtained by titrating the remaining basis in filtrate (Fig. 2). 

The usefulness of XPS in the study of the surface chemistry of carbonaceous materials is well established [120-123]. It is significant, however, that in 1994, while reviewing some aspects of the surface chemistry of carbon blacks and other carbons (in particular, active carbons), Boehm [48] devoted only a few lines to XPS and argued that XPS is not very useful for quantitative determinations. The selected examples included here are meant to give the reader an idea of the use of XPS in the last decade, often in combination with other methods such as FTIR and TPD, and more recently with solid-state nuclear magnetic resonance (NMR), for both qualitative and quantitative characterization of the surface chemistry (i.e., functional groups) either of raw carbonaceous materials or after their treatment (e.g., activation, thermal or chemical treatment, and pyrolysis). 

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