Introduction to polymer science

Introduction to Polymer Science

Polymer: 

The word polymers are derived from the Greek word poly means many and mers means unit or part. Polymers are chemical substances having very high molecular weight. Molecular weights of ordinary chemical substances are counted in ten or thousands. Whenever  Molecular weight of polymers are counted in  thousands and hundreds of thousands, because of the big size of the polymer molecules. They sometimes referred to as macro or giant molecules. They are built up of many small molecules joined together by chemical bonds.

                                    Example polyethylene                 

Monomer:

The word Monomer is derived from the Greek word Mono means one and mers means unit or part. Polymers are chemical substances having very high molecular weight. The small molecules of the substances from which a polymer is found is called Monomer or Monomers are low molecular weight compounds having a functionality of two or more are called Monomers.

Example ethylene                         

   

Polymerisation:

The chemical reaction by which monomer or in the case of co-polymerisation more than one monomer is converted to polymer is called polymerisation. Most generally the reaction may be represented as  

  

Where n is the degree of polymerisation usually n has high values.

Repeat unit:  

The structural unit enclosed by brackets is referred to as the repeat unit/monomeric unit.

End group:

End groups are the terminal units that terminate polymer chain where end groups are specified they are shown outside the brackets.

e.g.: CH₃ – CH₂  (CH₂ – CH₂)_n – CH = CH₂  End group.

D.P.→The degree of polymerisation refers to the total no of structural units including end groups and hence is related to both chain length and molecular a weight of the structural unit.

Monomer residue:

The remaining part of the monomer that is present in the polymer is called monomer residue.

The importance of polymer science to study for textile engineering:

(1)     Textile fibres are polymeric substance.

(2)     Size materials are polymer (used in weaving).

(3)     Printing thickeners are polymers.

(4)     Binders and fixers used in coloration with pigments are also polymers.

(5)     Many of finishing applied on textile goods are based on polymers.

(6)     Polymers are also used as wet processing aids.

Difference between polymer and ordinary chemical substance:

Properties	Polymer	Ordinary chemical
Molecular weight	High	Low
Dissolution	Slow,long time	Quick, less time
Solution viscosity	Very high	Low
Melting	Range of melting temperature	Short melting temperature

How do we write the name of a polymer?

If the name of monomer remain one words the name of the polymer is obtained by prefixing the word “poly” to the name of the monomer, such as polyethylene, polypropylene. If the name of the monomer consists of two or more words then we write the name of the polymer by poly ( name of the monomer) and poly ( poly vinyl, vinyl chloride)

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