| Plastic is the general common term
for a wide range of synthetic or semisynthetic organic amorphous solid
materials suitable for the manufacture of industrial products. Plastics
are typically polymers of high molecular weight, and may contain other
substances to improve performance and/or reduce costs.
The word derives from the Greek (plastikos),
"fit for molding", "molded". It refers to their malleability, or plasticity
during manufacture, that allows them to be cast, pressed, or extruded into
an enormous variety of shapes - such as films, fibers, plates, tubes, bottles,
boxes, and much more.
The common word "plastic" should not
be confused with the technical adjective "plastic", which is applied to
any material which undergoes a permanent change of shape (a "plastic deformation")
when strained beyond a certain point. Aluminum, for instance, is "plastic"
in this sense, but not "a plastic" in the common sense; while some plastics,
in their finished forms, will break before deforming — and therefore are
not "plastic" in the technical sense.
There are two types of plastics, thermoplastic
and thermoset. Thermoplastics, if exposed to heat, will melt in two to
seven minutes. Thermosets will keep their shape until they are charred
and burnt. Some examples of thermoplastics are grocery bags, piano keys
and some automobile parts. Examples of thermosets are kid's dinner sets
and circuit boards. |
