HIGH-FREQUENCY VISCOELASTICITY OF CARBON-BLACK FILLED COMPOUNDS

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, alpha, and sound velocity, v. Preliminary re sults were obtained for a number of filled and unfilled polymers. The grade of carbon black used, filler loading, crosslinking density and f iller dispersion were varied during the study. Temperature sweepS from -100 degrees C to +60 degrees C were also studied. It was found that the polymer type had a greater influence on alpha and upsilon than did the grade of carbon black, loading or dispersion. The experimental da ta show that shear waves do not propagate in the rubbery state. Above the glass transition temperature, T-g, the longitudinal wave measureme nts could be sufficient to determine the high frequency dynamic proper ties of filled and unfilled polymers to characterize a tire tread comp ound. The temperature sweep measurements allowed the determination of the T-g of polymers at high frequency. It is proposed that the describ ed method of measuring alpha and v be used as a laboratory tool for po tential tire traction prediction.