ABSTRACT
Good compounding goes for naught if tests of compound suitability are poorly chosen and/or improperly done. The best test for a compound is of course a service test. A prime example is the testing of tread compounds by road tests. Tread wear is developed quickly by continuous driving on courses of varying abrasiveness, usually in low traffic areas. Tear resistance is highest with crystallizable rubbers such as natural rubber, where strain induces crystallization and the crystals impede the tearing. In compounding for low temperatures, however, hysteresis may cause the internal heat developed in a rubber to warm the part well above the ambient temperature. Specifying a rubber part is accompanied by difficulties that are not experienced when metal parts are designed. Such difficulties are best overcome by having a performance specification, preferably citing a formula that has given satisfaction but not restricting the supplier to that example.
