What are plastics?

plastic (plas'tik)n&adj. safe, hygienic, tough, durable, lightweight, flexible, cost effective, convenient, good insulator, energy efficient, capable of re-use, recyclable.

"Plastic" comes from the Greek word "plastikos", which means mouldable. Plastic is a material that can be moulded into a shape and then set. Plastic is made out of giant chains of molecules. They can be natural like cellulose in wool or cotton or synthetically made by humans.

How is plastic made?

Polymer chemists use a process called polymerisation where gas molecules - mainly carbon and hydrogen - are cracked and transformed to become linked together in long chains. These molecules are up to 2,000 times bigger than a water molecule.

The type of atoms and the way they are linked in the chain gives the plastic created different characteristics - like strength, melt temperature, or resistance to chemicals. This means that there are hundreds of different kinds of plastics with very different sorts of uses. There are 2 main types:

• Thermosets are concrete like and can only be shaped once - polymer ingredients are reacted together inside a mould then left to set and harden
• Thermoplastics can be heated, melted, and reshaped many times - after being heated and softened they are shaped by putting the plastic under pressure so that it flows into a mould or through a die. The plastic then cools and sets into its shape. The six most common plastics are all thermoplastics.

For more technical information, try the links above, or these sites.