Measurement of Tensile Strength of Natural Rubber Vulcanizates at Elevated Temperature

Abstract

The tensile strength of test pieces made from natural rubber vulcanizates drops abruptly at a critical temperature which can vary from 40 to 130°C. This variation in critical temperature is shown here to be a result of the variation in critical cut length with temperature. When the naturally occurring flaws in the test piece are smaller than the critical cut length, high tensile strength values occur, but when the flaws are longer than the critical cut length, low tensile strength values occur. The critical cut length decreases as the temperature increases, and the abrupt drop in tensile strength occurs as the critical cut length reaches the natural flaw size in the test piece. The natural flaw size in tensile test pieces depends on the sharpness of the cutter, and for tensile strength measurements at elevated temperature, it is shown that even a slightly blunt cutter may give markedly different results from a sharp one.

A new paradigm for the molecular basis of rubber elasticity

“…Maximum stresses calculated range between 30 and 80 MPa and failure strains range between about 6 and 12, depending on the crosslink concentration. The reported experimental failure stresses (highest reported value) are: 32 [44], 20 [44], 25 [45], 16 [46], and 35 [47] MPa. The upper range of these values is within about a factor of two of the failure stresses predicted by our simulations.…”

Mechanical Properties and Fracture Surface Morphology of Clay-Filled Thermoplastic 1,2-Polybutadiene Rubber at Elevated Temperatures

“…It may be remarked that the data for elongation exhibit some scatter which is larger at higher temperature. Such scatter in tensile data has been reported for NR in the temperature range 80-120 "C. In this critical temperature range, tensile strength also showed an abrupt fall (Bell et al, 1982).…”

Transition of rupture mode of strain crystallizing elastomers in tensile edge-crack tests

“…Eqn (2) was experimentally validated using the edge-crack test of non-SIC rubbers by varying the initial notch length (c 0 ): 52 the strain energy density at break (W b ) is simply proportional to c 0 À1 , reflecting the fact that G is a material constant for non-SIC rubbers. By contrast, SIC rubbers exhibit a discontinuous transition in the W b -c 0 relationships: W b decreases with increasing c 0 , and notably, W b falls abruptly at a characteristic value of c 0 (c à 0 ), 36,[46][47][48] which is schematically shown in Fig. 1a.…”

“…Thomas et al assumed that the corresponding crack propagates like crack growth under cyclic loading. 36,46,47 When the notch grows by Dc during the loading, G is given from eqn (2) as follows:…”

“…1a. Thomas and coworkers 36,46,47 explained the experimental data for NR at c 0 4 c à 0 and c 0 o c à 0 using eqn (3) and ( 7), respectively. The W b values below c à 0 are significantly larger than those beyond c à 0 , reflecting the enhancement effect of SIC on the tearing energy.…”