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Polymers
Polymers are extremely large molecules that are essential to our very existence.
They are a main constituent of our food (starch, protein, etc.), our clothes
(polyester, nylons, cotton, etc.), our houses (wood cellulose, paints, etc.), and our
bodies (poly (nucleic acids), proteins, etc.).
The word polymer derived from a Greek words (poly) meaning many and (meros)
meaning part.
Types of Polymers
Polymers can be separated into plastics, fibers and rubbers. As engineering
materials, it is appropriate to divide them into the following three categories:
1. Thermo-plastic polymers
2. Thermo-setting polymers
3. Elastomers
Thermoplastic polymer can be heated from a solid state to a viscous liquid state
and then cooled back down to solid, this heating and cooling cycle can be repeated
multiple times without degrading the polymer.
By contrast, thermosets change chemically when heated, which cross-links their
molecules and permanently sets these polymers.
Polymer Synthesis
There are two major types of' polymerization methods used to convert small
molecules (monomers) into polymers. These methods were originally referred to as
addition and condensation polymerization. Addition polymerization known as
chain-growth, or chain- reaction polymerization. Condensation polymerization is
now referred to as step-growth or step-reaction polymerization.
