How far can natural rubber be stretched before it recovers its shape?

Natural rubber, which consists primarily of the polymer cis-1,4 polyisoprene, is characterized by its remarkable extensibility and toughness. It can be stretched repeatedly to seven or eight times its original length and still recover its shape.1

While some rubberlike materials can achieve elastic extensions of up to 1,000 percent, the ability of a material to return to its original form depends on its elastic limit. Beyond this limit, the material undergoes permanent deformation or flow. To enhance these properties and ensure the material remains resilient across a wider range of temperatures, natural rubber is typically subjected to vulcanization, a process that creates cross-links between the polymer chains.234