POLYMERS
Polymers: A polymer is a compound of high molecular mass formed by the
combination of a large no. of small molecules.
The small molecules which form therepeating unitin a polymer are called
asmonomers.
The process by which the monomers are converted into polymers is called as
polymerization.e.g.
n
CH2 = CH2
Polymerisation
ethene
– (CH2 – CH2 – )n
Polyethene
(monomer)
(Polymer)
Homopolymers and Co-polymers:
Depending upon the nature of repeating
structural unit, the polymers are divided into two categories:
1. Homopolymers: Polymers whose repeating structural unit is derived from only
one type of monomer unit are called as homopolymers.
e.g. in case of polyethene
n CH2 = CH2
ethene
– (CH2 – CH2 – )n
Polyethene
2. Co-polymers: Polymers whose repeating structural unit is derived from two or
more type of monomer units are called as copolymers.
e.g. in case of Nylon
66,
n H2N – ( CH2 )6 – NH2 + n HOOC –(CH2)4 –COOH
HexamethylenediamineAdipic acid
(monomer)
– n H2O
(monomer)
[– HN – (CH2)6– NH – OC –(CH2)4 – CO –]n
III Classification based upon Synthesis: On the basis of synthesis, polymers
can be classified as :
1. Addition polymers: In these polymers, the monomer units simply add on one
another, without losing molecule such as water, alcohol etc. This generally occurs
among molecules, which contain double bond. e.g.Polyethene, polystyrene,
polyvinyl chloride etc.
2. Condensation polymers: In these polymers, the monomer units combine
together with simultaneous loss of simple molecule such as water, alcohol
etc.e.g. Nylon,Terylene, Bakelite etc.
IV Classification based on Molecular Forces:
1. Elastomers: “Polymers in which the intermolecular forces of attraction are
weakest are called as elastomers.”
. Examples of elastomers are Vulcanized rubber, Buna-S etc.
2. Fibers: “Polymers in which the intermolecular forces of attraction are strongest
are called as fibres.”
Examples of fibers are nylons, terylene, decron, polyacrylonitrile etc.
3. Thermo plastics: “Polymers in which the intermolecular forces of attraction are in
between those of elastomers and fibers are called as thermoplastics”. Due to
less intermolecular forces of attraction, they can be easily moulded on heating.
Examples are polyethene, polystyrene, PVC , Teflon etc.
4. Thermo setting polymers: These are the polymers which undergo permanent
change on heating and become hard and infusible. On heating, they form crosslinks and become very hard. e.g. bakelite, melamine-formaldehyde resin etc.
Some Commercially important Polymers
I Addition polymers :
1. Polyethene or polyethylene:
(a) Low density polyethene (LDP):
n CH2 = CH2
ethane
473 K
1500 atm
(– CH2 –CH2 –)n
poly ethene
Uses : (i) As a packing material in the form of thin plastic films , bags etc.
(ii) In insulating wires & cables.
(iii) In the manufacture of toys, bottles etc.
(b) High density polyethene(HDP) : It is prepared by the polymerization of
ethene in the presence of Triethylaluminium& Titanium tetrachloride ( known
as Zeigler - Natta catalyst).
n CH2 = CH2
340 K, 6-7 atm
(– CH2 –CH2 –)n
(C2H5)3Al + TiCl4
Uses : in the manufacture of buckets, tubs, bottles, toys, pipes etc.
4. Polyacrlonitrile (PAN) or Orlon:
(–CH2 – CH–)n
n CH2 = CH
I
I
CN
CN
Vinyl cyanide (acrylonitrile)
Polyacrylonitrile
Uses: for making blankets, sweater, carpets etc.
6. Poly vinyl Chloride (PVC):
n CH2 = CH
I
Cl
(–CH2 – CH–)n
I
Cl
Vinyl chloride
Polyvinylchloride (PVC)
Uses: (i) In making rain coats, hand bags, plastic dolls, shoe-soles, vinyl flooring
etc.
(ii) As an insulating materials for wires & cables.
(iii) In making gramophone records & hose pipes. etc.
7. Polytetraflouro ethylene (PTFE or Teflon) :
heat
(–CF2 –CF2–)n
n CF2= CF2
press.
tetraflouroethylenepolytetraflouroethylene(teflon)
Uses: (i) As a martial resistant to heat & chemical attack.
(ii) For coating of non- stick cook wares.
(iii) For making gaskets, pump, packing, valves, seals, non-lubricated
bearings etc.
II. Condensation Polymers: These are of followingthree types:
(A) Polyesters
(B) polyamides
(C) Formaldehyde resins
O
II
(A) Polyesters: They involves ester ( – C – O – ) linkage. e.g.
1. Terylene (or Decron) :It is a polymer of ethylene glycol and terephthalic acid.
n HO – CH2 – CH2–OH + n HOOC
ethylene glycol
–[O – CH2 – CH2– O – OC
COOH
terephthalic acid
–nH2O
425K
CO –]n
Terylene (or Decron)
Uses: (i) For making cloth by mixing with cotton.
(ii) For making magnetic recording tapes, tyrecord , seat belts etc.
2. Glyptal: It is a polymer of ethylene glycol and phthalic acid
HOOC
COOH
–H2O
n HO–CH2–CH2–OH + n
OC CO
– O–CH2–CH2–O–
Glyptal
Uses: (i) In the manufacture of paints and lacquers.
(ii) For making building material such as asbestos, cement etc.
O
II
(B) Polyamides:
These involve amide (–C– NH –) linkage. e.g.
1. Nylon – 6,6 : It is a polymer of hexamethylenediamine and adipic acid.
n H2N – ( CH2 )6 – NH2 + n HOOC –(CH2)4 –COOH
– n H2O
HexamethylenediamineAdipic acid
[– HN – (CH2)6– NH – OC –(CH2)4 – CO –]n
Uses: (i) in making bristles for brushes.
(ii) In textiles e.g. in making soaks and sweaters by mixing with cotton.
2. Nylon 6, 10 : It is a polymer of hexamethylenediamine and sebacic acid .
n H2N – ( CH2 )6 – NH2 + n HOOC –(CH2)8 –COOH
– n H2O
HexamethylenediamineSebacic acid
[– HN – (CH2)6– NH – OC –(CH2)8 – CO –]n
3. Nylon- 6 ( orPerlon) : Its monomer is called as caprolactum, which is obtained
from cyclohexane, Caprolactum is hydrolysed to get ε-amino caproic acid which
is then polymerized to obtain Nylon-6.
O
Oxidation
  
H
NOH
NH2OH
  

– H2 O
H2SO4
 
N
N
O
cyclohexanecyclohexanonecyclohexanoneoximecaprolactum
H2O, 
Δ, Polymerisation
[– HN – (CH2)5–CO –]n 


Nylon-6
H2O
H2N – (CH2)5 – COOH
ε -Aminocaproicacid
Uses: In making tyres, fabric, ropes etc.
2.
Melamine–formaldehyde Resin: Melamine and formaldehyde
copolymerization to form Melamine –formaldehyde resin as shown:
undergo
Uses: It is used in making unbreakable crokerye.g cup, plate, tray etc.
Natural Rubber: It is prepared from Latex, which is obtained from Rubber trees. It
is a polymer of 2- methyl 1,
3 butadiene (isoprene)
Vulcanized Rubber: As natural rubber becomes soft in summer and hard in winter,
therefore it is improved by the process Vulcanization. It involves heating of
natural rubber with 3-5% suplhur. Sulphur forms cross- links between polymer
chain and thus make rubber harder & stronger.
S
S
Sulphur
 
S
S
S
Heat
S
S
Synthetic Rubbers:
1. Neoprene:
Uses:
(i) In making bells , hoses , shoe-heals, stoppers etc.
(ii) In making containers for storing petrol & oils.
2. Buna–S : ( or SBR) : It is prepared by copolymerization of 1,3 butadiene and
styrene , in the presence of Sodium.
3. Buna-N: Itis a copolymer of 1,3- butadiene and acrylonitrile (vinyl cyanide),
uses: (i) For storage of petrol, lubricating oils and organic solvents.
(ii) In making oil seals, hoses and tank livings
Some Commercially Important Polymers:
BIODEGRADABLE POLYMERS
VSA of One Mark
1. What is the Monomer present in Un Breakable Plastics.
2.
3.
4.
5.
Name the monomer present in Non stick appliances.
Give one application of Bekalite.
Name the monomer present in Nylon-6?
What does designation 6,6 mean in the name Nylon 6,6?
SA-1 of Two Marks
1. Arrange the following polymers in an increasing order of their intermolecular
forces.
Ans:
(i) Nylon- 6,6, Buna – S , Polythene
(ii) Nylon- 6 , Neoprene, Polyvinyl chloride.
Buna - S,Polythene, Nylon- 6,6
Neoprene, Polyvinyl chloride ,Nylon- 6
2. What are the biodegradable polymers? Give one example of a biodegradable aliphatic
polyester .
Write the structures of monomers used and one use of each of
3. the following
polymers. (a) Teflon (b) Buna – N
4. Differentiate between addition and condensation polymers with suitable
example of each.
5.
SA-2 of Three Marks:
1. Explain following process with example
Chain growth polymerization.
Step growth polymerization.
2. What is Vulcuonization? How does it changes the properties of natural rubber?
3
4. Write the information asked for in the following polymers:
i) Bakelite – materials used for preparation
ii) PVC – Monomer Unit.
5. Describe Free radical mechanism in polythene.