Elongation

Elongation

Elongation is defined as the length at breaking point expressed as a percentage of its original length (i.e. length at rest). If a rubber reaches twice its length before breaking its elongation is 100%.

Importance

To qualify an elastomer mechanically for its applied usage, it is necessary to measure the force needed to get a sample to its rupture point. Understanding the elongation for elastomers is important for determining the best option to use by our customers. Pulling a rubber sample will lead to rubber deformation. As the sample gets longer, sections will get reduced that will eventually lead to a break.

Measurement

The test method determines the variability in rubber vulcanizates and the influence of parameters affecting the stress-strain properties such as temperature, relative humidity, and the preconditioning of rubber.

A traction device, called a dynometer, has an extensometer that optically or mechanically follows 2 marks on the sample. The dynometer can measure, at any time, the size of the rubber test sample during the extension pulling stage, and when the breaking point arrives.

Bone-shaped samples are stretched in the narrow section where the two marks are made. O-ring samples are often rotated during extension so that no specific zone is affected. Rotation speed is included in the results.

Calculating

When gauge marks or extensometers are used to define a specific test section, only this length is used in the calculation, otherwise the distance between the grips is used as the initial gauge length.

Results/Reporting

The elongation is expressed as a percentage, and is reported out to two significant figures.

elongation percent = (elongation at rupture) x 100/(initial gauge length)

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