Experimental Study of Low-Frequency Effects on the Dynamic Modulus of a Buna-N Rubber

Abstract

Abstract The linear dynamic Young's modulus of a vulcanized Buna-N gum rubber was measured at frequencies of 0.05, 0.10, and 1.00 cps, in the temperature range − 22° C to 30° C, by a method in which a small differential sinusoidal elongation is superimposed on a 5 per cent static elongation. The width of the dispersion range on the temperature scale (the range in which the logarithm of the modulus increases steeply with decreasing temperature) is only about 10° C, contrasted with widths as great as 25° C found in previous measurements on a similar compound at frequencies of several kilocycles. The modulus-temperature plot shifts upward by only about 4° C per decade of frequency increase of the present range, contrasted with about 10° C per decade in the previous measurements at higher frequencies. It is concluded that this elastomer cannot be described properly by means of the “method of reduced variables”, in which the dynamic properties are ascribed to mechanisms having identical temperature dependence, and that the low-temperature behavior is governed by mechanisms distinct from those effective in the audio-frequency range at room temperature.