Set Tension Compression

The test involves stretching the sample to a constant strain (generally 100% or 25%, 50%, 200%, or 300%). The sample is held at the desired strain for a fixed period before the load is removed and the sample allowed to stabilize. The increase in length of the markers is the permanent set. The methods are detailed below. 

Determination of tension set under constant elongation, and of tension set, elongation, and creep under constant tensile load Standard test methods for vulcanized rubber and thermoplastic elastomers-tension Testing of rubber and elastomers 

Determination of tension set after constant deformation Physical testing of rubber part A5 Method for determination of tension set at normal and high temperatures 

The test is composed of marking the desired length on the dumbbell, stretching the sample to the desired elongation, and holding at that elongation for a set period of time. The time duration may be 24, 72, or 168 hours. The temperature may be ambient, 70, 85, or 100°C. The test time starts 30 minutes after the sample is introduced, and the final measurements are made after 30 minutes of recovery. 

Samples of polyurethane are clamped between two plates so that they are compressed by 25%. The samples may be tested at ambient or 70°C. They are compressed for either 24 or 72 hours. After compression they are allowed to recover for 30 minutes and then remeasured. The methods are detailed below. 

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