Fourier transform rheometry on carbon black filled polybutadiene compounds

A series of high cis‐1,4 polybutadiene compounds with various levels of N330 carbon black were prepared and tested using a Rubber Process Analyzer RPA® (Alpha Technologies), suitably modified for so‐called Fourier transform rheometry. Strain sweep test protocols were used in order to capture strain and torque signals, that were consequently treated through Fourier transform calculations, using the appropriate proprietary software. Through strain sweep tests, the non‐linear viscoelastic behavior was investigated, with significant odd‐harmonics detected in the torque response, not only as the strain magnitude increases but also as the carbon black level increases. Differences in non‐linear behavior, due to growing filler level are easily and clearly detected and the dependence upon strain of the relative third harmonic component is adequately modelled with simple four parameter models. Two such models were compared and found to give similar results, both offering two parameters to describe the strain sensitivity. First derivatives of the models allow a single number, i.e., the slope at a given strain, to be calculated as a “quantification” of the strain sensitivity, and hence of the non‐linear character. Carbon black volume fraction appears then as the main compounding parameter influencing the non‐linear viscoelastic response. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 5102–5118, 2006