Material Chemistry:Plastics: Properties and Uses
Plastics are synthetic materials, that is, they don't occur naturally. They're made in chemical factories from crude oil or natural gas, extracted by drilling underground or beneath the sea bed. Plastics can be divided into two main groups: thermoplastics and thermosets. Thermoplastics soften, then melt, when they're heated. As the plastic cools, it hardens in whatever new shape it's been given. But when you heat a thermoset, it doesn't melt. Instead, the heat causes the material to break down. This change can't be reversed, so thermosets can't be recycled.
- Added：2006
- Country：Australia
- Duration：21
- Time of update：2011/3/11 15:03:55