Page 30 - Curriculum Visions Dynamic Book

The properties of plastics
Plastics are a group of carbon-based materials that scientists often refer to as polymers. They vary greatly, but they have a number of properties in common.
•Most plastics are not very strong and could not, for example, replace steel in uses such as the frames of buildings.
•Most plastics are easy to bend.
•Many plastics will change shape if they are pulled. •Many plastics are not very hard and will scratch easily. •Many plastics are not very dense, that is, they are quite
lightweight materials. Some will float in water; most of the
others are only just a little denser than water.
•Many plastics are very brittle at low temperatures, that is,
they will harden and crack easily in very cold conditions. •Many plastics soften easily when they get hot (and so cannot be used for things like oven-based cookware).
However, there are exceptions, such as nonstick materials. •Plastics expand about ten times as much as metals as they
get hotter.
•Many plastics are destroyed by fire (they decompose),
even though they do not actually burn.
•Most plastics are very good electrical insulators, and
so can be used to insulate cables, for plugs and
sockets, etc.
•Plastics tend to become brittle with age. This
is especially so with those exposed to direct
sunlight (ultraviolet radiation).
•Plastics are mostly very resistant to being
broken down by chemical attack, and they are not water-soluble, which is why they do not decompose when placed out in the open or buried.
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