What Makes a Rubber Band Stretch?

Rubber bands are made of rubber. Since rubber, which has been used by humans since ancient times, is an elastic material that provides insulation against water and heat, is a soft and long-lasting material, it has a wide usage area today. It is a macro molecule called rubber isoprene, formed by connecting small molecule units to each other. The polymer chains that make up the rubber are located in an intertwined, soft-like state. Chemical bonds can occur between different polymer chains in the rubber's structure. This event is called crosslinking.

When the rubber band is stretched, the interlocked polymer chains open and become flat. When the applied force is removed, the polymer chains return to their former shapes. What makes the molecules return to their old entangled states is cross-linking between different polymer chains.

The elasticity of the rubber band after it is stretched is due to this feature of rubber. However, if the force exerted on the package tire is large enough to cause the breakage of the bonds between the different polymer chains, the elongated rubber band cannot be restored.