When you buy a new packet of rubber bands they are usually dry, stretchy and you expect them to last a few weeks, even out in the weather, but after some time the rubber changes. It loses its stretch and it cracks, and eventually becomes sticky and useless. Why is this?

Natural rubber, or latex, is a gooey, sticky fluid. But when some chemicals are added it becomes tougher and stronger. It is made of polyisoprene chains, which slip past each other when they are stretched, and the great thing about rubber is its resistance to change. It can return to its original state when the tension is released.

Man?s ingenuity has found that the addition of sulphur, which creates cross-links between the chains, turns a useless product into a useful one, but when rubber is exposed to sunlight, the ultraviolet reacts with oxygen and snips the polyisoprene chains into shorter and shorter segments, until it returns to a state similar to its original. Meanwhile, the molecules of short segments form new cross-links and alter the structure of the runner. It becomes brittle and harder.

Rubber may also contain fillers, dyes and other chemicals, which all contribute to its breakdown over time. The process can be speeded up if the rubber is warmed a few degrees, and slowed down if it is cooled. It can also be speeded up if the rubber is stretched, because this causes the molecules to move closer to each other, allowing the radicals to jump across the chains and form new links.

The fact that rubber perishes is a universally observed phenomenon, and it comes as part of a general rule: whatever Man makes will eventually break down, perish, rust, and fall apart. It is a universal law. All complex things become less complex over time.

The Second Law of Thermodynamics operates everywhere. A new car slowly becomes an old car, a new set of clothes slowly becomes rags, a brand new house will eventually need to be demolished. Nothing is immune. Moving out from Manmade objects we find the same Law operating in the natural realm. Stars burn out, orbits decay, mountains erode, plants and animals spring up fresh and new but soon they age , wither and die.

Richard Gunther, Copyright 2006

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