Heat Build-Up and Blow-Out of Rubber Blocks
AKRON UNIV OH INST OF POLYMER SCIENCE
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Rubber blocks heat up under repeatedly-applied severe deformations and sometimes explode blow out. This phenomenon is shown to be due entirely to the high temperatures developed internally, about 200 C, which cause decomposition of the vulcanizate, and generation of a volatile product. When the internal pressure is high enough, the surrounding rubber is torn apart and the sample bursts. The same process can be observed with a microwave oven, when the rubber sample is heated internally, without stress, to the same critical temperature Tc. Values of Tc are reported for different vulcanizates of several elastomers. They are found to be lower for softer materials, in accord with the theory of elastic expansion to burst of internal gas bubbles, and lower for materials having less stable crosslinks for example, polysulfidic instead of monosulfidic or C-C cross-links. Maximum values of Tc were about 240 C, significantly below the temperatures for rapid decomposition of the elastomers themselves. Possible reasons for this anomaly are discussed. Keywords Explosive rupture FractureMechanics Heating Thermal decomposition.
- Elastomers and Rubber