Tensile strength is the force required to rupture a specimen of a given elastomer when subject to stretch at a constant rate. Tensile strength is measured in psi (pounds per square inch) or MPa (Mega Pascals).
Tensile strength is a very common quality assurance measurement used in the rubber industry to ensure compound uniformity. It is also useful as an indication of deterioration of the compound after it has been in contact with a fluid for long periods. If fluid contact results in only a small reduction in tensile strength, seal life may still be relatively long, yet if a large reduction of tensile strength occurs, seal life may be relatively short. Exceptions to this rule do occur and should be investigated on a case by case basis with a Parker applications engineer.
Tensile strength is not a proper indication of resistance to extrusion, nor is it ordinarily used in design calculations. However, in dynamic applications a minimum of 1,000 psi (7 MPa) is normally necessary to assure good strength characteristics required for long-term sealability and wear resistance in moving systems.