polymer and their types

1. General Chemistry-(unit iv)
syllabus
Unit-IV Polymers- definition-explain the following with suitable
examples- addition polymerisation-condensation polymerization.
b) fibres-definition-manufacture and uses of important fibres-polyamide
fibre- polyester fibre.
c) resins-definition-manufacture and uses of amino resin, unsaturated
polyester resin
d) plastics- definition- classification of plastic- thermoplastics- thermo
setting plastics-manufacture and uses of polythene and poly vinyl
chloride

2. Polymers- introduction
Fibres, resins and plastics are the different forms of polymers.
definition
 A polymer (Greak : many parts ) is a macromolecule of high
molecular weight. It is built up by the repetition of small molecular
called monomers. The process is termed polymerization.
Types of polymer
The polymers which occur in nature are known as natural polymers
or bio-polymers e.g. starch, cellulose, protein and rubber.
 Many polymers have been prepared by synthesis and used in our
daily life. They are known as synthetic polymers.
Ex: Polyethylene, Bakelite, Teflon, silicone and polyester

3. Polymerization reactions:
Polymerization reactions are mainly of two types:
• Addition polymerization
• Condensation polymerization
Addition polymerization:- It is a process in which the polymer is formed by the addition
of two or more unsaturated monomers. Monomers of the same type yield
homopolymers while those of different types produce copolymers.
1) n CH2 = CH2 → (-CH2 –CH2 -) n
Ethylene Polyethylene
(homopolymer)
2) n CH2 = CH –CH =CH2 + n C6 H5 – CH =CH2 → (-CH2 – CH = CH - CH2 - CH2 – CH -) n
Butadiene Styrene SBR (Copolymer) C6 H5
 It is a chain reaction intimated by heat, Light or a catalyst. The addition polymers have
linear or branched chain structures.

4. Condensation polymerization :- It is a process in which the polymer is
formed by the addition of polyfunctional monomers followed by the
elimination of small molecules such as water.
n HO – R –OH- + n HOOC-R’-COOH → (-O-R-OCOR’-CO-)n + 2n H2O
Bi-functional Bi-functional Polymer
Monomer Monomer
 It is a stepwise polymerization reaction. The polymers have cross
linked structures.

5. FIBRES- definition
Polymers in the form of filaments or threads which can be woven or spun into fabrics
are called fibres. A fibre may be defined as a filament whose length is atleast 100
times its diameter.
Polyamide fibres :- These are generally known as nylons.
They are having properties identical with silk and are therefore, called artificial silk.
The nylons are described by a numbering system that indicates the number of carbon
atoms of the monomers.
Nylon 6,6 -manufacture
 It is a condensation polymer of hexamethylene diamine and adipic acid the
monomers contain 6 carbon atoms each.
n H2 N (CH2)6 NH2 + n HOOC (CH2)4 COOH → (-HN (CH2)6NHOC(CH2)4CO-)n + 2nH2O
Hexamethylenediamine Adipic acid nylon 6,6

6. Nylon 6: manufacture
It can be synthesized by the ring opening polymerization of caprolactam.
Caprolactam is a cyclic amide with 6 carbon atoms. The polymerization
reaction is carried cut by heating the monomer with water at 250°C,
n HN - (CH2)5 –CO+ H2O → n H2N (CH2)5 COOH → (-HN (CH2)5CO-)n + n H2O
caprolactam amino caproic acid Nylon 6
H OH H H N

7. Uses:-i) Nylons are used extensively for making parachutes, glider ropes,
conveyor belts, carpets, fishing nets and automobile tyre cords .
ii) Coarse nylon is used in toothbrushes, paint brushes, tennis rackets and
undergarments.
iii) Nylon sheets and films are used for cable insulation taps and packaging.

8. Polyester fibres :- manufacture:There are made by the condensation of
polytunctional acids or esters with polyfunctional alcohols. Terylene or Decron is a
popular polyester fibre. It is produced by heating dimethyl terephthalate and
ethylene glycol a 200°C in the presence of a base as catalyst.
n CH3 OOC –C6H4 – COOCH3 + n HOH2C – CH2OH → (- OC-C6H4-COOH2C-CH2-O-)n + 2nCH3OH
DMT(dimethylterephthalate) ethylene glycol Terylene

9. Uses :
i) Polyester fabrics have outstanding crease retention and wrinkle resistance.
Slight wrinkles when wet, disappear on wearing due to body heat. They are
therefore, used in wash and wear clothing.
ii) Polyester fabrics blended with natural fibres to get quality fabrics like tery-
cotton –tery-wool and tery- silk. They have the good qualities of both the
cellulose fabrics (moisture absorption and ventilation and the polyester
fabrics (wrinkle resistance, crease retention and heat insulation). Thus, they
provide better appearance and wearing comfort.

10. Iii) Polyester fibres are also used for making conveyor belts, fishing
nets, parachutes and automobile tyre cords.
Iv) Terylene can be extruded into a thin film called mylar film. It has
extreme stiffness and toughness and hence used for making cassette
recording tape and photographic film.

11. RESINS-definition
 Carleton Ellis defined resin as solid or semisolid amorphous mixture of
organic substances, having no definite melting point and showing no
tendency to crystallize.
Types:
 Resins occur widely in plants and animals. These are called natural resins.
 However, a number of resins are now a days prepared by synthesis from
non biological materials. These are termed synthetic resins.
RESIN- introduction
 The term resin refers to naturally occuring amorphous solid or semisolid,
translucent, brownish or yellowish organic substances, mostly of vegetable
origin, exuding from the barks of many varieties of trees and shrubs.
 Chemically it is a mixture of carboxylic acid, essential oils and terpenes.

12.  resins are rosin and balsam obtained from coniferous trees. Shellac is a
natural resin obtained from the secretions of an Indian insect.
 In general resins have a strong pleasant odour. They are hard and
brittle when cold.
 They are combustible and electrically non-conductive.
 They are insoluble water but soluble in organic solvents.
 They are widely used varnishes, adhesives and electrical insulation .
 synthetic resins which are man made high polymers resulting from an
addition or condensation reaction, with heat or a catalyst. Unlike natural
resins which are mixtures of simple substances, synthetic resins
polymeric compounds. Thus synthetic resins do not have chemical
resemblance with natural resins.

13. The first synthetic resin developed by Backeland, in 1911 was phenol-formaldehyde
resin.
they are insoluble in water, resistant to attack by chemicals and highly non conductive
Based on their properties, synthetic resin can be divided into thermoplastic resin and
thermosetting resins .
 They are used in plastics, textiles and paints.

14. • Amino resin (or)Urea formaldehyde plastic :-manufacture: Urea and
formaldehyde react to give resins which when mixed with fillers like flour
and colouring matter, produce plastic. It is prepared by condensing urea
and formaldehyde at about 330K.
• Uses: It is thermosetting in nature. It is widely used in the manufacture of
adhesives, plywood, fibres, crease-resisting textiles, etc.

15. Glyptal (or) unsaturated polyester resin:
It is a polyester having cross linkages. It is manufactured by the action of phthalic acid on
glycerol.
Uses:
• Composite materials
• It is a thermosetting plastic. It is used as coating in the lacquer and paint industry
• Wood paints, bathroom fixtures
• Self-extinguishing composite materials
• Quartz, marble and artificial cement

16. PLASTICS -introduction
• Plastics are synthetic high polymers mixed with other modifying materials
such as fillers, colouring matter, plasticizers, catalysts, etc. and they are
capable of being moulded, with or without the application of heat.
Distinction between synthetic resins and plastics:
• Synthetic resin is a high polymer by itself. But plastic is a polymer
mixed with other additives such as plasticizers, colouring matter, fillers, etc.
in other words, synthetic resins are the basis of many plastics.
• Celluloid was the first plastic produced in 1869. It was a mixture
of cellulose nitrate and camphor. Backelite, a condensation product of
phenol and formaldehyde was introduced by backeland in 1907. Bakelite is
the first truly synthetic high polymer. It is a substitute for shellac, a natural
resin.

17. Classification:
Plastic may broadly be classified into two group namely
(i) Thermoplastic
(ii) Thermosetting
Thermoplastics:
 These are linear polymers having long chains with a few chemical bonds acting as cross links
between the chains.
 Such plastics when heated, become soft and they can be remoulded into useful shape.
 They are soluble in many organic solvents.
 Examples:Polystyrene, polythene, polymethyl methacrylate, PVC
Thermosetting plastics
 These are normally semi fluid substances with low molecular weight.
 Under heat and pressure, they become highly cross linked and get moulded.
 On reheating they become highly cross linked and get moulded.
 On reheating they will not soften again.
 These three dimensional polymers are insoluble in almost all solvents.
 Examples: Backelite, urea-formaldehyde plastic and glyptal

18. • Polythene (or) polyethylene : It is produced by polymerizing ethylene at
high pressures between 1000-3000 atmospheres and at temperature
between 100- 300°C in the presence of peroxide .
n CH2 = CH2 → (-CH2 –CH2 -) n
Ethylene Polyethylene
• It is a thermoplastic. It is resistant to water , acids, alkalis and many organic
solvents. It is inexpensive also. It is used in making package sheets, non-
breakable bottles, pipes, laboratory chemical wares and also in wire and
cable insulation.

19. • Polyvinyl Chloride (PVC) is obtained by the polymerization of vinyl chloride in the
presence of H2O2 or benzoyl peroxide at about 40°C under pressure.
• It is then mixed with plasticizers (dibutyl phthalate and cresyl phosphate),
stabilizers like white lead and red lead lubricant, fillers and pigments. The
resulting plasticised PVC non–inflammable and thermoplastic. It is stable to heat
and light. It’s softening temperature in high. It is used in industry, especially for
moulding articles.