Adsorption and Calorimetric Investigations on Carbon Black Surfaces I. Immersional Energetics of Heat Treated Channel and Furnace Blacks

Abstract

Adsorption of gases under reversible conditions on carbon blacks can provide important basic information revealing the highly heterogeneous nature of the surface electronic fields and relating to physical interactions between the black and elastomeric molecules. Precise, immersional, calorimetric measurements likewise document the strongly heterogeneous surface energies and provide a powerful technique for measuring both physical and chemisorptive interactions between the surface and organic adsorbates. In the first phase of this study a broad spectrum of channel and reinforcing furnace blacks has been studied by immersional calorimetry to provide a survey of both integral and, to a lesser extent, differential heats of adsorption using methanol, n-decane, benzene, and water as adsorbates. The blacks studied were thermally treated at appropriate temperatures so that a wide span of surface conditions could be investigated, including the entire range of coverage by oxygenated functional groups and the regions of maximum hydrogen evolution and incipient graphitization. With these heat-treated blacks, marked integral immersional heat differences between channel and furnace blacks were observed with some adsorbates but not with others, and these results are discussed in terms of black surface conditions. Subtle differences between furnace blacks revealed by differential immersional heats are also presented.