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The relative residual strain after stretching of a TPE sample or product is often a decisive factor in material selection. Although thermoplastic elastomer products such as carpets, children’s toys, medical devices, and seals mainly operate under compression, many technologists and end users still “stretch” them to evaluate the rubber-like properties of the material.
Relative residual strain after stretching is defined as the percentage ratio of the increase in length of a specimen after stretching to its original length before stretching.
This parameter depends on the hardness of the material and, consequently, on the proportion of plastic in the TPE formulation. TPEs from different manufacturers with the same hardness can show significantly different residual strain values. Low-quality grades with very little rubber in their composition effectively transform the material from an elastic band into a “soft rag.”
When comparing TPEs with rubber, the results are often not in favor of TPEs. TPEs can stretch 7–10 times before breaking, while rubber typically stretches only 2–3 times. However, under equal conditions—for example, when both are stretched to 200–300% elongation—the recovery of TPE and rubber is comparable. The most widely used TPE grades on the market, with hardness of 55–70 Shore A, exhibit relative residual elongation after rupture of about 80–150%.
By contrast, the LCS grades we produce demonstrate relative residual elongation after rupture of only 30–35%.
