Classification of polymer

Classification of polymer

Thousands of different polymers have been synthesized and more will be produced in the future. Conveniently, all polymers can be assigned to one of two groups based upon their processing characteristics or the type of polymerization mechanism. A more specific classification can be made on the basis of polymer structure. Such groupings are useful because they facilitate the discussion of properties

Classification based on broad sense.

(a)    Biological polymer.  e.g – D.N.A, R.N.A, Protein.

(b)    Non- biological / Industrial polymer:  e.g. fibre, plastic, rubber, adhesive materials, coating materials.

Classification of Industrial Polymers:

1. On the basis of origin / source

(i) Natural: Those isolated from natural material

                              e.g cotton, silk, wool, rubber, Cellulose rayon.

(ii) Synthetic: Polymer synthesized from low molecular weight compound.          

                                  e.g. Polyethylene, Poly vinyl chloride

2. On the basis of chemical nature of the polymer,

(i) Inorganic: Polymer generally contains no carbon atom in their chain backbone.               

                                  e.g.  Glass, Silicon, Rubber etc

(ii) Organic: A polymer whose backbone is essentially made of carbon atom.   

                                   e. g.  poly ethylene, PVC, Nylon.

3 On the basis of behavior towards heat :

All polymers can be divided into two major groups based on their thermal processing behavior. 

(i) Thermo plastic: Polymer which soften on heating and stiffen on cooling are termed Thermoplastic. 

Those polymers that can be heat-softened in order to process into a desired form are called thermoplastics. Waste thermoplastics can be recovered and refabricated by application of heat and pressure. Polystyrene is an important example of a commercial thermoplastic,    e.g.- Polyester, nylon.

(ii) Thermo setting: Polymers which become infusible and insoluble mass on heating are called Thermo setting.

In comparison, thermosetsare polymers whose individual chains have been chemically linked by covalent bonds during polymerization or by subsequent chemical or thermal treatment during fabrication. Once formed, these crosslinked networks resist heat softening, mechanical deformation, and solvent attack, but cannot be thermally processed. Such properties make thermosets suitable materials for composites, coatings, and adhesive applications. Principal examples of thermosets include epoxy, phenol–formaldehyde resins, and unsaturated polyesters that are used in the manufacture of glass-reinforced composites such as Fiberglas

                                                    e.g. Urea formaldehyde, Melamine formaldehyde.

                                     

                                    

4 On the basis of geometrical structure of polymer:

(i) Straight: Having no branching in the polymer backbone.

                                e.g. polyethylene

(ii) Branched: Having branching in the polymer backbone.

                                e.g. PVC, PVA,

(iii) Cross linked: Having cross-linked between and among polymer chain.               

                                  e.g.- Urea Formaldehyde, Melamine Formaldehyde

5 Based on form and use:

(i) Fibre: A fiber or staple fiber is a unit of matter which is usually at least 100 times longer than      its thick.                                     e.g. – Polyester, nylon

(ii) Elastomer: When vulcanized into rubbery products exhibiting good strength and elongation , polymers are used as elastomers.

                                      e.g. – Rubber

(iii) Plastics: When a polymer is shaped into hard and tough utility articles by the application of hear and pressure it is used as a plastic  

                                       e.g.  PVC

6. Based on monomer present:

(i) Homopolymer: When the unit are all the same and are joined linearly (a linear polymer), the polymer is a homo-polymer and it’s structure may be represented as [M] _n where M is the repeat unit and n is the no of repeat units or degree of polymerisation (D.P).

(ii) Co-polymer:  When more than one type of repeat unit is involved the polymer is called copolymer.                                          Example-PVC  

7. Based on the mechanism of Polymerisation:

(i) Chain Polymer: e.g. Polyetylene

(ii) Step or condensation:

8. Based on side chain present :

(i) Isolatic:   When a polymer chain grows if the vacanted orbits arranged at the same position all the time, incoming monomeric units are inserted with the same spatial arrangement resulting the isotatic polymer.

(ii) Syndoitactic:  When a polymer chain grows, the insertion of each monomeic unit if migrates from one position to the other er alternatively spatial arrangement resulting syndiotactic.

(iii) Alactic: When a polymer chain grows if the vacanted orbits arranged randomly is called alactic


In the next tutorial you will get total classification of polymerization. so stay with
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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)