C2 material choices

One way of comparing materials is to measure thier properties.

Properties of materials can include:

• melting points,
• strength (in tension and compression)
• stiffness
• hardness
• density

When choosing a material for use it helps to have an accurate knowledge of it's properties.

Polymers are materials which are made up of long-chain molecules.

There are natural polymers such as cotton, paper, silk and wool.

There are synthetic materials which are alternatives to materials from living things.

There are many examples of modern materials made of synthetic polymers that have replaced older materials such as wood, iron and glass.

Crude oil is made mainly of hydrocarbons.

Most of the materials from oil are fuels and only a small percentage of crude oil is used to make new materials.

Refining crude oil produces some small molecules which can join together to make very long chain molecules; this process is called polymerization.

Polymerization produces a wide range of plastics, rubbers and fibres.

The properties of polymer materials depend on how the long molecules are arranged and held together.

It is possible to modify polymers to change their properties. This includes modifications such as:

• Increasing the length of the chains.
• cross-linking the molecules. (this makes the material stronger)
• Adding plasticizers to lubriate the movement of molecules. (this makes the material more flexible)
• Crystallinity by liking the molecules (this makes the material stronger and stiffer)