Abstract - Non-linear Viscoelastic Characterization of Natural Rubber Gum through Large Amplitude Harmonic Experiments


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	Publications of MRB Latest Publications MRB Digest Journal of Rubber Research 3^rd Qtr 2008 Vol 11(3) 2^nd Qtr 2008 Vol 11(2) 1^st Qtr 2008 Vol 11(1) 4^th Qtr 2007 Vol 10(4) 3^rd Qtr 2007 Vol 10(3) 2^nd Qtr 2007 Vol 10(2) 1^st Qtr 2007 Vol 10(1) 1^st Qtr 2006 Vol 9(1) 2^nd Qtr 2006 Vol 9(2) 3^rd Qtr 2006 Vol 9(3) 4^th Qtr 2006 Vol 9(4) Submit paper/article Order Form	Abstract Non-linear Viscoelastic Characterization of Natural Rubber Gum through Large Amplitude Harmonic Experiments J.L. Leblanc Standard dynamic testing requires strict proportionality between stress and strain for valid resolution of the (measured) complex modulus into its elastic and viscous components. Thus, it is restricted to material and/or testing conditions that correspond to linear viscoelastic behaviour; otherwise ‘apparent’ results are obtained, with therefore limited meaning, if any, in terms of material science. Correct non-linear harmonic testing under large amplitude oscillatory strain is however feasible today using purposely modified torsional rheometers to capture full strain and torque signals which are appropriately treated in order to extract pertinent and useful information. Harmonic techniques that require signal processing to convert the response of the material in the time domain into a material property in the frequency domain are usually referred to as Fourier Transform (FT) rheometry, i.e. a development of the so-called dynamic (or harmonic) testing to investigate both the linear and the non-linear viscoelastic domains of polymer materials. It consists essentially of considering the frequency spectrum of the torque signal obtained when submitting a material to high strain. Contrary to standard dynamic testing, no validity condition is needed for FT rheometry. In principle, any dynamic rheometer can conveniently be modified for FT testing, but implementation of the technique on a commercial torsional rheometer, operating with a closed test cavity, proved to give repeatable and reliable results on a number of polymer systems. A series of natural rubber gum samples were tested in order to further illustrate the capabilities of the technique. back
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