Advanced torsional dynamic methods to study the morphology of uncured filled rubber compounds

Uncured compounds of SBR1500 with various levels of silica were studied using a torsional dynamic tester (rubber process analyzer; RPA). Silica-filled compounds were prepared with the appropriate amounts (8.2%) of silane, i.e., bis(3-triethoxysilylpropyl)tetrasulfane (TESPT). A carbon black-filled compound was also studied for comparison. Strain sweep tests at constant frequency show that filled rubber materials exhibit either no or limited linear viscoelastic domain. Frequency sweep tests were performed either at the lowest strain amplitude or within the linear range at several temperatures; results were treated through time-temperature superposition in order to yield G' and G" master curves at the reference temperature of 100 degreesC. Special test procedures were applied that are known to give interesting information about the morphology of complex polymer systems: the morphology damaging test (MDT) and the damaged morphology recovery test (DMRT). Results obtained are discussed with respect to the likely morphology of carbon black and silica-filled rubber compounds. (C) 2001 John Wiley & Sons, Inc.