Elongation or Elastically of Foam

Unit of Measure	%
Test Method	JIS K6767-1976

Elongation @ Break is the elongation of the foam recorded at the moment of rupture of the specimen, often expressed as a percentage of the original length. It corresponds to the breaking or maximum load. In layman’s terms it is the amount the foam can stretch before it snaps. A “brittle” foam will have a lower figure than a foam that is more like warm chewing gum.

This test is done in conjunction with the Tensile Strength test, using the same dumbbell shaped piece of foam. The ends are pulled apart, and the amount of stretch is measured at the time of breaking.

Calculation of Elongation @ Break (E),

E = (l₁ – l₀) / l₀ x 100

For example, calculate the Elongation @ Break of EVA45:

Using our dumbbell shaped test piece we measure a length of 0.040m prior to testing and mark this on the sample, thus giving us l₀ = 0.040m.

The Tensile Strength test is then performed, and the sample length had stretched to 0.150m at the time of breaking, thus giving l₁ = 0.150m.

From above, E = (l₁ – l₀) / l₀ x 100

          Where,  l₀ = 0.040m

                        l₁ = 0.150m

          Therefore                E = (0.150 – 0.040) / 0.040 x 100

                                            = 275%

Thus, the Elongation @ Break of this example is 275%.

The graph shows that typically EVA foam is much more elastic than PE foam.