Specific Shape Characterization of Carbon Black Primary Units

Abstract

Abstract A full field feature specific image analysis system has been developed for direct morphological characterization of carbon black in the electron microscope. The system provides quantitative size and non-dimensional shape information, as well as qualitative classification into specific shape categories using pattern recognition programming methods. Data on samplings of 500–1000 primary black units can be recorded on magnetic tape in less than 10 minutes. Although not yet tested on a full range of rubber grade blacks, the new system has demonstrated good sensitivity in resolving morphological differences among a series of four HAF blacks of varied DBP absorption. The blacks exhibited large frequency variations across nine specific shape categories which range from spheroidal to fibrous types. Within each category, the unit size and non-dimensional shape factors were similar for all four blacks. On a composite average basis, however, large differences in unit size (longest dimension or projected area), anisometry (length/width ratio), and irregularity (perimeter/area ratio) were observed. The new image analysis system also has the capability of volume measurements based on microdensitometry. Although data is limited at this time, such measurements should provide more three-dimensional approximations of carbon black unit size. It is also anticipated that microdensitometry will aid in the determination of domain (particle) size.