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ROBOTS AND HUMANS
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PLASTIC
 What are the properties of plastic?
Well, there are two main families of plastics - thermosets and thermoplastics and they've got quite different properties.
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Thermosets
These are hard, strong and very heat resistant. There are quite a few different types of thermosetting plastics. They're used for things like electrical plugs and sockets, kitchen work surfaces, kettles and special adhesives like epoxy resin. Thermosetting plastics don't melt if they're heated, but instead, they tend to char or burn.
Thermoplastics
These are tough, easy to mould and flexible. Two types of thermoplastics - polypropylene and polythene are used to make boxes and bags. PVC is used to make drainpipes, window sills and inflatable boats because it is resistant to damage from ultraviolet light - which can cause other types of plastic to break down. Polycarbonate is a very tough thermoplastic used in police riot shields and some windows. Thermoplastics will melt if they are heated up.
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What are the other properties of plastic?
Plastics are very good electrical insulators - which is why electrical wires are covered with plastic. Most plastics are resistant to corrosive chemicals like acids and alkalis but they may be damaged by organic solvents like ethanone. Plastics are also light - around five or six times less dense than steel. Gamma radiation will pass easily through plastic.
Robot Constructor and plastic
You should be aware that the behaviour of the plastic coded into the software in Robot Constructor is thermoplastic.
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STEEL
What about steel? What is it, and what are its properties?
Steel is an alloy (a metallic substance composed of two or more elements) made from iron and small amounts of carbon. The addition of the carbon makes steel much stronger than iron and the more carbon the steel contains the harder it becomes. Unfortunately harder steel is more brittle.
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Image courtesy of Sir Robert McAlpine Ltd
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What types of steel are there?
Mild steel contains under 0.3% carbon. It is the softest, cheapest and therefore the most common type of steel. It's used for things like nuts and bolts, ships and car bodies.
Tool Steel contains about 1% carbon. It is used to make tools like chisels and screwdrivers. It is possible to make this high carbon steel even harder by heating it to 820 Celsius and quenching it in water.
Stainless steel is made by adding small amounts of the metal chromium to the steel when it is being manufactured. Stainless steel is highly resistant to oxidation (which makes steel rust) and is very hard and strong. It is used to make cutlery, sinks and saucepans.
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What are the other properties of steel?
Steel is magnetic and being a metal, conducts electricity. It is strong and relatively light and has a high melting point - over 1000 Celsius. All steels, except stainless steel react with oxygen in the atmosphere to produce rust. They also corrode if exposed to acid. Gamma radiation will pass easily through steel plate.
Robot Constructor and steel
You should be aware that the behaviour of the steel coded into the software in Robot Constructor is mild steel.
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LEAD
What are the properties of lead?
Lead is a soft, grey metal with a low melting point - just 327 Celsius. It's very dense - about nine times as dense as plastic and about one third more dense than steel. Lead's high density makes it ideal for shielding sources of gamma radiation and X rays. The rays aren't always stopped but their intensity is greatly reduced. The thicker the lead shielding, the better. Lead is also very inert (chemically unreactive) which makes it resistant to attack from corrosive chemicals like acids and alkalis.
Robot Constructor and lead
If you make your robot from lead, it will be very heavy and so will require large amounts of energy to make it move. However it will be able to survive radioactive zones without any trouble.
HUMANS
What are humans made of?
Humans and more or less all other living things are made of a relatively few elements. Mostly carbon, hydrogen, oxygen and nitrogen. There is also some phosphorus, sulphur, magnesium, calcium and iron. Materials that hold our body in shape, support it and help it move are skin, bones and muscles, tendons and ligaments.
The skin
The skin is the external cover of the body and as such, it holds the body in shape, is waterproof and protects us from injury, dirt and bacteria. It has receptors in it which make it sensitive to touch, pain, pressure and temperature. It also has special glands which secrete sweat, and help to regulate body temperature. Fat is stored under the skin, which acts as insulation and a food reserve.
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The skeleton
The human skeleton provides the body with support and protects internal organs, like the lungs, heart and brain. It moves the body with the help of muscles. While the outside of the bones are hard, the inside is made of soft bone marrow. This is where the red blood cells are made. Bones need muscles to make them move. They are attached to the bones by tendons. Tendons contain collagen fibres which resist stretching. A ligament is a strip of connective tissue, which links two bones together. It is flexible but is packed with collagen fibres which strongly resist stretching.
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MATERIALS robots & humans
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