Abstract
It is generally accepted that the internal area arising from pores in an oxidized carbon black does not contribute to performance characteristics in rubber. While such pores are available to nitrogen, commonly used in evaluating surface area, they do not appear to be accessible to an elastomer molecule. Thus in predicting performance from area measurements one should consider the external area. Of course, for a non porous black the external and total (BET) area will be identical. In the past, the electron microscope provided the only independent means of evaluating external area. However, with the development of oil furnace blacks, particularly the more recent grades of high structure, identification and measurement of individual particles becomes more difficult and the electron microscope procedure less reliable. However, in recent years the so called “t curve” procedure has come into prominence and appears to provide a useful comparative method for detecting porosity and, to a degree, its extent. The method is quite empirical and requires the selection of a “non porous” adsorbent to serve as a standard with which other samples may be compared. A number of standards have been proposed but that of de Boer appears to be most widely used. The de Boer standard is based on a calcined alumina. In undertaking porosity studies on carbon blacks it appeared to us from earlier studies on silicas and titanias that a non polarizing carbon would be preferable to an oxide surface. Accordingly, we have selected a fine thermal black as a t curve standard. The present paper presents some of the results of this study. They differ to a degree from those of other investigations in which the de Boer standard was employed.
Two Different Type Nitrate Aerosols in the Winter Polar Stratosphere: Morphology of Individual Particles Observed with an Electron Microscope.
