Some plastics have high tensile strength and resistance to stretch (high modulus), but have low elongation. Most rubbers, on the other hand, have high elongation but low tensile strength and modulus. Polyurethane elastomers have high elongation, high tensile strength and high modulus. This combination provides toughness and durability in fabricated parts, and is one of the distinctive characteristics of polyurethane elastomers.

Generally, the harder the elastomer, the less it will permit elongation. However, the ability of polyurethane elastomers to achieve higher hardnesses while maintaining good elongation permits them to withstand higher tensile loads without the risk of rupture.

Test Procedure to Measure Tensile Strength ASTM Method D412
The maximum tensile stress which a material is capable of developing. It is the force per unit of the original cross-sectional area which is applied at the time of rupture of a specimen. It is known variously as "breaking load," "breaking stress" and "ultimate tensile strength." A dumbbell specimen is used for the test.

Test Procedure to Measure Elongation ASTM Method D412
The extension between benchmarks produced by a tensile force applied to a specimen as a percentage of the original distance between the marks. A dumbbell specimen is used for the test. Ultimate elongation is the elongation at the moment of rupture.

Test Procedure to Measure Break Set
A tensile force is applied to break a benchmarked dumbbell specimen. A period of relaxation follows after which the two parts are fitted together and the distance between the marks is remeasured. The difference between the new measurement and the original is expressed as a percentage of the original distance.

Test Procedure to Measure Tensile Modulus ASTM Method D412
The force per unit of original cross-sectional area required to stretch the specimen to a stated elongation. 50%, 100% and 300% extensions are commonly used. The test is performed on a dumbbell-shaped specimen.