DYNAMIC VISCOELASTIC PROPERTIES OF CARBON-BLACK LOADED CLOSED-CELL MICROCELLULAR ETHYLENE-PROPYLENE-DIENE RUBBER VULCANIZATES - EFFECT OF BLOWING AGENT, TEMPERATURE FREQUENCY, AND STRAIN

Dynamic mechanical analysis of carbon black loaded solid and closed-ce ll microcellular ethylene-propylene-diene (EPDM) vulcanizates was stud ied at four frequencies of 3.5, 11, 35, and 110 Hz and temperatures fr om -100 to 150 degrees C. A plot of the log of the storage modulus bea rs a linear relationship with the log of density for solid as well as closed-cell microcellular rubber. The slope of the line is found to be temperature-dependent. The relative storage modulus decreases with de crease in the relative density. It was also observed that the storage modulus and tan delta are both frequency- and temperature -dependent. The storage modulus results are superposed to form master curves of th e modulus vs. log temperature-reduced frequency, using shift, factors calculated by the Arrhenius equation. Strain-dependent isothermal dyna mic mechanical analysis was carried out for DSA varying from 0.07 to 5 %. The effect of blowing agent loading on the storage modulus (E') and loss tangent (tan delta) were also studied. Cole-Cole plots of microc ellular rubber shows a circular are relationship with the density. Plo ts of tan delta against E' were found to exhibit a linear relationship . (C) 1996 John Wiley & Sons, Inc.