Title: Plastics
Course: Technology > Section: Materials

PLASTICS

PLASTICS

Definition: Plastics are materials formed by polymers

from wikipedia

The word plastic is derived from the Greek πλαστικός (plastikos) meaning "capable of being shaped or molded", from πλαστός (plastos) meaning "molded".It refers to their malleability, or plasticity during manufacture

Polymers are long chains that are composed of many repeated subunits called monomers

CLASIFFICATION DEPENDING ON THEIR ORIGIN

There are two kinds of plastic materials: natural and synthetics. They are usually synthetic, most commonly derived from petrochemicals, but many are partially natural.

Natural plastics are obtained directly from raw materials (vegetable or animal proteins) such as latex, cotton, casein.

Synthetic plastics are made from processed materials extracted from petroleum, natural gas and carbon.

CLASSIFICATION DEPENDING ON THEIR STRUCTURE

Plastics are usually classified by their chemical structure.

Thermoplastics

Most plastics belong to this group. They are formed by weakly-linked chains criss-crossed in different directions. This weak linkage permits thermoplastics to be remoulded at high heat many times.

Thermostables

They are formed by strongly-linked chains criss-crossed in different directions. This strong linkage is irreversible, and once applied cannot be undone.

Elastomers

They are formed by strongly-linked lateral chains. They have a very organized structure which permits them to be very elastic and resistant. Elastomers plastics can be or thermoplastics either thermostables.