Influence of the blend composition in the internal friction of NR/SBR compounds

Mechanical dynamic measurements were used in this work to analyze the behav ior of cured, carbon black-filled NR/SBR blends using a sulfur/accelerator system. The loss tangent (tan delta) of the compounds was studied in the fr equency range between 10(-3) and 10 Hz and temperatures between 80 and 260 K. Measurements were performed with an automated sub-resonant forced pendul um. A new model was applied to loss tangent data, based on the consideratio n of the phase network. A secondary transition (beta relaxation) appears in the blends at temperatures between 100 K and 160 K, in addition to the gla ss transition. This peak is analyzed in terms of the rotation of the cis an d vinyl units from butadiene of SBR.