Natural polymers: The polymers which occur in nature i.e., which occur

either in plants or animals, are called natural polymers. For example,

natural rubber, proteins, cellulose, starch (polysaccharides), wood, silk and

nucleic acids are natural polymers.

Synthetic polymers: Synthetic polymers are man-made polymers. These

polymers are made in laboratories or factories. Typical examples of

synthetic polymers include polyethene, PVC, nylon, terylene, Teflon,

synthetic rubber, Bakelite and melamine.

Semi-synthetic polymers: Chemically modified natural polymers are

called semi-synthetic polymers. For example, nitrocellulose, cellulose

acetate etc. are termed semi-synthetic polymers. These polymers are also

called chemically modified natural polymers.

Linear chain polymers: The polymers m which the constituent monomers

link with each other to form a long straight chain are called linear chain

polymers, or straight chain polymers.

Linear polymers are well packed and thus have high densities, high tensile

strength and high melting points. For example, high-density polythene

(HDPE) is a linear chain polymer.

Branched chain polymers: The Polymers which have side-chains

attached to the linear chains consisting of monomers are called branched

chain polymers.

The branched chain polymers are irregularly packed and thus have lower

tensile strength, lower melting point and lower density. For example,

low-density polythene (LDPE) has lower density, lower melting point and

lower tensile strength than the linear high-density polythene (HDPE).