Rupture of rubber. VII. Effect of rate of extension in tensile tests

An autographic method is described for obtaining loadextension curves of ring specimens extended at various rates from about 0.1 to 2000% per second. Results showing the effect of the rate of extension on the tensile strength and breaking extension and on the load-extension curve are given for a GR-S gum vulcanizate and for two GR-S vulcanizates containing carbon black. The tensile strength of the gum vulcanizate, at the temperatures at which the tests were carried out, increases uniformly with the rate of extension, but the tensile strength of the filled vulcanizates passes through a maximum. The effect of the rate of extension on the load-extension curve of the gum vulcanizate is that to be expected from the viscoelastic properties of the material; the effect in the case of the filled vulcanizates is more complex. These results are briefly discussed.