The word POLYMER is a combination of two greek words, poly means “many”and meros means ”parts or unit”.

The polymer is a large molecule, which is formed by repeating linking of the small molecules called ‘’MONOMER”. the monomer may be identical or may be different

Polymers are large molecules made up of many smaller and identical repeating units joined together by covalent bond.

Polymers are of mainly tow types 

1. Thermoset polymer
2. Thermoplastic polymer

Thermoset polymer:-

Thermosets having the property of becoming permanently hard and rigid when heated or cured .

Such polymers that become in fusible and in soluble mass on heating are called thermosetting polymers.In general, unfilled thermosetting plastics tend to be harder, more brittle, and not as tough as thermoplastics. Thus it is common practice to add filler to thermosetting materials. these are the polymers that are set for permanently. it can not recyclable .

phenol resins and plastics are original thermosetting materials.

  example of thermosetting polymer:-

• Bakelite (phenolic)
• Cyanate esters.
• Duroplast.
• Epoxy resin.
• Fiberglass (a fiber-reinforced thermoset)
• Melamine.
• Polyester resin.
• Polyurethane.
• Silicone resin
• Vinyl esters
• Vulcanized rubber

Thermoplastic polymer:-

A type of polymer that can soften by heat , hardened by cooling , and then soften by heat over and over again. Thermoplastics are not cross linked.

such polymers that soften on heating and stiffen on cooling are termed as thermoplastics{thermo means temperature}. these are the polymers that reacts on temperature variation. it can be recyclable and reuse.

example of thermo plastic polymer:-

• polyethylene,
•  polypropylene
•  polyvinyl chloride, 
• polystyrene,
• ABS
•  polyamides,
•  polyesters
•  polyurethanes
•  polyetherether ketones,
•  liquid crystalline polymers,
•  polysulfones,
•  and polyphenylene sulfide.

thermo plastics are of two types

• semicrystalline
• amorphous

Semicrystalline polymer:-

Semicrystalline materials display crystalline regions, called crystallites, within an amorphous matrix. 

a polymer never be  a fully crystalline it is always semi crystalline in nature.

these are opaque in nature because most part of the polymer is crystalline and less part is amorphous .the polymer is mostly crystalline and its atoms are regularly arranged . That is why light can not pass through closed pack structure .and the polymer are mostly opaque .

• polyamides,
•  fluoropolymers,
•  polyurethanes,
•  biomedical polyesters etc

Amorphous polymer:-

in an amorphous polymer the molecules are arranged randomly and are intertwined and the polymer has a glass like transparent appearance.{irregular arrangements of atoms}.

these are transparent in nature because of its irregular arrangements .light can easily pass through irregular pattern.

• PS
• PMMA
• SAN
• PVC 
• PS 

thank you .