A summary of the latest efforts to characterize carbon black and the latest findings using state-of-the-art scientific instrumentation is presented. Over the years, advanced studies of furnace carbon black formation and characterization have helped the rubber technologist to better predict the performance of the end product (i.e., a tire) but still today these characteristics are not totally sufficient and more work is necessary to better define and describe the exact nature of carbon black produced using the furnace process.

The filler dispersion is an essential rubber compound characteristic. Traction, treadwear, and rolling resistance are affected by filler dispersion. The quantification of dispersion is a length scale phenomenon. The existing experimental tools, which are capable of measuring dispersion, for example transmission electron microscopy (TEM), mechanical scanning microscopy (MSM), optical microscopy, and reflectometry, have limitations and the information they provide may not probe the relevant scale length. The recent advance in instrumentation allows one to include electrical measurements in the arsenal of tools available to quantify the dispersion. This paper reviews the range of dispersion measurements and the correlation with compound dynamic properties is presented.

A high frequency viscoelasticity spectrometer, using the state-of-the-art ultrasonic technology, was constructed. The longitudinal and shear waves characteristics were measured in rubber compounds to obtain the attenuation coefficient, α, and sound velocity, v Preliminary results were obtained for a number of filled and unfilled polymers. The grade of carbon black used, filler loading, crosslinking density and filler dispersion were varied during the study. Temperature sweepS from −100°C to +60°C were also studied. It was found that the polymer type had a greater influence on α and v than did the grade of carbon black, loading or dispersion. The experimental data show that shear waves do not propagate in the rubbery state. Above the glass transition temperature, Tg, the longitudinal wave measurements could be sufficient to determine the high frequency dynamic properties of filled and unfilled polymers to characterize a tire tread compound. The temperature sweep measurements allowed the determination of the Tg of polymers at high frequency. It is proposed that the described method of measuring α and v be used as a laboratory tool for potential tire traction prediction.

A new method of measuring carbon black dispersion in rubber is presented. This method is based on the measurement of the light reflectivity from the rubber sample using standard equipment used in the evaluation of the tint strength of carbon black (ASTM D3265 procedure). This method can be applied for both uncured and cured samples; however, the uncured sample measurement has significant advantages in the simplicity of the sample preparation and obtaining important filler dispersion information of the compound. It is shown that samples with better dispersed carbon black reflect less light as compared to samples with poor carbon black dispersion.