Why can natural rubber stretch and return to its original shape?

Natural rubber is an elastomer, a material composed of long, chainlike molecules known as polymers. Under normal conditions, these molecules exist in an irregularly coiled, compact state.1

When force is applied to the material, these long chains straighten out in the direction of the pull, allowing the rubber to stretch to great lengths. Once the force is released, the molecules spontaneously return to their original, random, and compact arrangement, causing the material to recover its shape.12

While these molecular properties provide inherent elasticity, natural rubber is often modified through vulcanization—a process involving the addition of sulfur to create cross-links between the polymer chains. This chemical interlinking creates a stable molecular network that prevents the material from flowing like a liquid when warm and improves its overall resilience and durability for practical applications.34