Page 4 - Curriculum Visions Dynamic Book

1: The nature of fibres
A fibre is a slender thread or strand of material.
It appears so fragile that you could be forgiven for thinking that it had no use at all. But a spider uses it to make a web so tough it will hold a fly, we use it to make the clothes we wear, and parachutists put their whole lives at risk and rely entirely on the special properties of fibres.
So how could such slender threads have found a place that is central to our lives? The answer lies in the fact that a fibre is much more than it appears to be.
Just as a chain appears to be no more than a thread when seen from afar, so a thread is far more complicated than it appears to be to the human eye.
The key to understanding everything about threads is to know that they are nearly all made of molecules arranged in a very special way. Fibres contain what are known as giant molecules and are made of simple repeating patterns of atoms bound together in such a way as to give a fibre incredible strength, flexibility, and elasticity. We will look at how molecules are linked together on page 10.
Fibres and filaments
There are two kinds of threads or strands of
material. When you talk about a fibre, you are talking about a thread that has a definite length. Cotton is a fibre formed in the cotton seed (boll). An extremely long (effectively endless) strand of material, as made by a silkworm or in a factory, is more accurately called a filament.
(Above and right) A spider sends out a fine, never-ending sticky thread, or filament, as it makes
its web. These filaments, often referred to as “silk,” are made inside the animal’s body and pushed out through a tiny opening in the abdomen. This process is called extrusion, and it produces a single filament that is as long as the spider wants to make it. Filaments of this kind are made of proteins.
(Below) The world contains a bewildering variety of fibres. Some are natural, such as the spider’s web opposite; others are entirely a result of human effort in a chemical factory. But nearly all of them have this in common: They are made of long chains of molecules with carbon running along their “backbones.”
See Vol. 1: Plastics to find out more about sheets of material.
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