CURE AND MECHANICAL-BEHAVIOR OF RUBBER COMPOUNDS CONTAINING GROUND VULCANIZATES .2. MOONEY VISCOSITY

Mooney viscosities and thixotropic behavior have been determined for S BR melts containing carbon black and/or ground vulcanizate particles. A composition containing ambiently ground rubber has a higher viscosit y than one with cryogenically ground rubber. This is attributed to occ lusion of continuum rubber within the sponge-like, ambiently ground ru bber; occlusion is not possible with the smooth, cryo-ground particles . Viscosity was independent of particle size. On an equal phr (weight) basis, the addition of N330 carbon black and cryo-ground rubber augme nt Mooney viscosity to a similar extent. While the Guth-Gold Equation is approximately applicable to black-filled melts, samples containing ground rubber are a much better fit by the simple Einstein Equation. G round rubber addition has only a minor influence of thixotropy, in con trast to carbon black, which greatly increases thixotropy.