CHAPTER:POLYMERS

POLYMERS

The macromolecules which consist of large number of repeating units are known as polymers. They have high molecular masses .Mostly they  have organic origin i.e. they contain backbone chain of carbon atoms.

E.g. Polythene, rubber, nylon etc.

MONOMERS

The repeating units of polymers are called monomers. They  are linked together by covalent bond.E.g polythene is a polymer  of  ethene monomers.

POLYMERIZATION

The process of formation of polymers from monomers is known as polymerization.E.g. large number of ethene monomers undergoes polymerization to form polyethene.

                                                     

           

                          

HOMOPOLYMERS :- The polymers which are made up of only one type of monomers are called homopolymers. E.g. polythene is a homopolymer because it consists of only one type of monomers called ethenes.some other examples are ,nylon,isoprene,etc.

                              

                               

           COPOLYMERS: - The polymers which are made up of two or more types of monomers are known as copolymers.The process of formation of a copolymer is known as copolymerization.

                                  

                              

               

(3) ON THE BASIS OF STRUCTURE

                                                                                        THREE TYPES

          (i)  LINEAR POLYMERS                      (ii)  BRANCHED-CHAIN POLYMERS                 (iii)    CROSS-LINKED POLYMERS

(i) LINEAR POLYMERS :- The polymers  having strait chain structure are known as linear polymers.E.g. High-density polythene,PVC,Novolac,Nylon-66 etc.

                                                        

(ii) BRANCHED CHAIN POLYMERS :- The polymers having branched chain structure are called branched-chain polymers.E.g. Low-density polythene, Glycogen, Starch, Vulcanized rubber etc.

                                                          

(iii) CROSS-LINKED POLYMERS:- The polymers having cross-links between the chains are called cross-linked polymers.E.g. Bakelite, Melamine formaldehyde resin etc.

                                           

                                                           (4) ON THE BASIS OF INTERMOLECULAR STRUCTURE

                                                                                                           FOUR TYPES

                                                                       

(i) FIBRES                            (ii) ELASTOMERS                       (iii) THERMOPLASTICS        (iv) THERMOSETTING POLYMERS

(i) FIBRES :-The polymers in which long chains are held together by strong intermolecular forces are called fibres.E.g. Terylene,Silk,Nylon-66 etc.

(ii)ELASTOMERS: - The polymers in which long chains are held together by weak intermolecular forces are called elastomers.They are elastic in nature.E.g.Buna-s,Natural rubber, Neoprene etc.

(iii)THERMOPLASTICS :- The polymers  whose strength of intermolecular forces lies in-between that of fibres and elastomers are called thermoplastics.They soften on heating and stiffen on cooling.E.g.PVC,Polythene etc.

(iv)THERMOSETTING :-The polymers which get changed into an infusible mass on heating are called thermosetting polymers.They do not get soften on cooling.E.g.Bakelite,Melamine formaldehyde resin etc.

Q:-What are PLASTICIZERS?

Ans:-The organic  compounds which are used to soften stiff and hard polymers like PVC are called plasticizers. E.g.Dialkylphthalates,phthalates etc.

                   

(5) ON THE BASIS OF MODE OF POLYMERIZATION

             TWO              TYPES

                (i) ADDITION POLYMERS                                                                                    (ii) CONDENSATION POLYMERS

(I) ADDITION POLYMERS :-The polymers which are  formed by the addition of monomers  without the removal of simple molecules are called addition polymers.E.g. Polythene, Nylon, Isoprene, PVC etc.

ADDITION POLYMERIZATION:-The process of formation of addition polymers is known as addition polymerization.E.g. Polythene is a addition polymer formed by addition polymerization as follow:

                                              

(ii)CONDESATION POLYMERS:-The polymers which are formed by the condensation of monomers with the removal of simple molecules like water, ammonia etc are called condensation polymers.E.g. Bakelite, Melamine, Terylene, Nylon-66 etc.

CONDENSATION POLYMERISATION:-The process of formation of condensation polymers is known as condensation polymerization.E.g.Nylon-66 is a condensation polymer formed by condensation polymerization of monomers hexamethylene diamine and adipic acid.as follow:

Q:-Explain chain growth polymerization or addition polymerization?

Ans:-It is a process of formation of polymers by successive addition of monomers in a chain.The reaction is initiated by some active species such as free radical or ionic species.E.g. formation of polythene,PVC,Polypropene etc.

                                                            

Q:-Explain step growth polymerization or condensation polymerization?

Ans:-It is a process of formation of polymers  through a series of reactions which take place in a stepwise manner.It involves condensation of monomers  with the removal of simple molecules like water,ammonia etc.E.g. polymers like Nylon-66,Bakelite etc.

Q:-Explain free radical mechanism of addition polymerization or chain growth polymerization?

Ans: FREE RADICAL MECHANISM: This mechanism involves three steps

(i)CHAIN INITIATION

(ii)CHAIN PROPAGATION

(iii)CHAIN TERMINATION

(i)CHAIN INITIATION:-In this step alkenes initiate  polymerization in the presence of free radical initiator like Benzoyl peroxide.It undergoes homolytic cleavage to form bezoyl free radical which gets attached to ethene to form another large sized free radical.

                       

(ii)CHAIN PROPAGATION:-In this step free radical combines with other molecule of ethene to form still bigger radical and this step is repeated again and again.

       

(iii)CHAIN TERMINATION:-In this step bigger free radical formed in step two combines with another free radical to form polythene.

Q:-Give name and structure of monomers, type,  preparation and uses of following polymers.

               

1)POLYTHENE

                                                                                                 TWO TYPES

                                                    

                                                     (a)   LDPE                                                                                        (b)  HDPE

(a)   LOW DENSITY POLYETHENE

(i)              It is a branched polymer hence it has low density.

(ii)            Its monomer is ethene.

                      CH₂=CH₂

(iii)           It is a homopolymer.

(iv)           It is a addition polymer.

(v)             It is prepared by addition polymerization in the presence of a free radical as initiator.

                                                  

USES  OF LDPE

(i)         It is used as packing material in the form of thin plastic bags.

(ii)       It is used to insulate electrical wires and cables.

(iii)      It  is used to prepare flexible pipes ,toys and squeezing bottles.  

(b)  HIGH DENSITY POLYETHENE

(i)           It is a linear polymer and hence it has high density.

(ii)          Its monomer is ethene.

CH₂=CH₂

(iii)        It is a homopolymer.

(iv)        It is an addition polymer.

(v)                  It is prepared by addition polymerization in the presence of  a catalyst called Ziegler-Natta catalyst[(C₂H₅)₃Al + TiCl₄ ].

                                           

USES OF HDPE

(i)         It is used to prepare buckets, tubes, dustbins etc.

(ii)       It is used to prepare different house wares, pipes, bottles etc.

(2) TEFLON OR POLYTETRAFLUOROETHENE

               (i)   Its monomer is Tetrafluoroethene.

                    CF₂=CF₂

   (ii)  It is a homopolymer.

   (iii)  It  is an addition polymer.

    (iv) It is prepared by addition polymerization  in the presence of a catalyst  at high pressure.

                                           

USES OF TEFLON

(i)   To  prepare non-sticky  cooking utensils.

(ii) To  prepare gas-kits, valves, oil-seals etc.

3) POLYPROPENE OR POLYPROPYLENE

(i)  Its  monomer  is Propene.

         CH₃-CH=CH₂

(ii) It  is  a  homopolymer.

(iii) It is an addition polymer.

(iv) It  is prepared by addition polymerization.

                                                     

USES OF POLYPROPENE

It is used to manufacture ropes, toys, fibres, pipes etc.

4) POLYISOPRENE OR NATURAL RUBBER

i) It  is obtained from rubber trees in the form of  a white milky liquid  called latex.Chemically latex is a colloidal  solution of rubber particles in water.

ii) It is a linear polymer.

iiI)  Its monomer is  Isoprene whose IUPAC  name is  2-methylbuta-1,3-diene or 2-methyl-1,3-butadiene.

                                                      

iv) It  is a homopolymer.

v) It  is an addition polymer.

iv) It  is prepared by addition polymerization of  isoprene monomers.

                          

vii) Polyisoprene  has two configurations.

       (a) cis-polyisoprene

       (b) trans-polyisoprene

viii) Cis-polyisoprene is called natural rubber. It has coiled structure and hence it is elastic and non-crystalline in nature.

 

ix) VULCANIZATION :- The process of heating natural rubber with sulphur to improve its properties is known as vulcanization.During this process  cross-links are established between the straight chains.The vulcanized rubber becomes hard, non- sticky and resistant to abrasion.

                       

USES OF NATURAL RUBBER

i)  To prepare rubber bands.

ii) To prepare adhesives.

iii) To prepare rubber hoses.

iv) To make heart valves.

v) The vulcanized rubber is used to make tyres, ebonite and battery cases.

DIFFERENTIATE BETWEEN NATURAL RUBBER AND VULCANIZED RUBBER

NATURAL RUBBER        1) Soft and sticky 2)Low tensile strength 3)Low elasticity 4)Low abrasion resistance 5)Soluble in organic solvents.

VULCANIZED RUBBER 1) Hard and non-sticky 2)High tensile strength 3)High elasticity 4)High abrasion resistance. 5)In soluble in organic solvents.

(5) POLYCHLOROPRENE OR NEOPRENE OR SYNTHETIC RUBBER

i) Its monomer is Chloroprene. Its IUPAC name is 2-chlorobuta-1,3-diene.

                                                         

ii) It is a homopolymer.

iii)It  is an addition polymer.

iv) It  is prepared by addition polymerization in the presence of  free radical.

              

USES  OF NEOPRENE

I) It is used for manufacturing conveyor belts, gaskets and hoses.

II) To prepare adhesives.

III)In making shoe heels , stoppers etc.

IV) To manufacture pipes for petrol.

(6)POLYACRYLONITRILE (PAN) or ORLON

i) Its monomer is vinyl cyanide or acrylonitrile, or cyanoethene.

                    

ii)It  is a homopolymer.

iii) It is an addition polymer.

iv) It  is prepared by addition polymerization  of  acrylonitrile  in the presence of peroxide catalyst.

                 

USES  OF ORLON

i)To  prepare synthetic carpets.

ii) To prepare blankets, sweaters, bathing suits etc.

iii) It is used for manufacturing conveyor belts, gaskets , hoses, printing rollers.

iv) To prepare adhesives.

v) To prepare commercial fibres  under the name Orlon.

7) POLYVINYL CHLORIDE (PVC)

1) Its monomer is Vinyl Chloride or Chloroethene.

                         

2) It  is a homopolymer.

3) It is an addition polymer.

4)It  is prepared by addition polymerization.

           

USES  OF PVC

i)To insulate wires and cables.

ii) To prepare rain coats ,hand bags and water pipes.

iii) To make gramophone records.

8 POLYSTYRENE

i) Its monomer is called Styrene.

            

ii) It  is a homopolymer.

iii) It is an addition polymer.

iv) It  is prepared by addition polymerization.

         

USES  OF POLYSTYRENE

I)It is used as an insulator.

II)It is used as wrapping material.

III)To prepare toys, radio and T.V cabinets.

(9)POLYMETHYL ACRYLATE (PMA)

i) Its  monomer is known as Methylacrylate.

             

ii) It is a homopolymer.

iii) It is an addition polymer.

iv) It  is prepared by addition polymerization  of  Methyacrylate.

          

USES  OF PMA

i) In making hoses.

ii) To make  carpets and blankets.

iii) To prepare latex paints.

(10)POLYMETHYLMETHACRYLATE(PMMA)

i) Its commercial names are Lucite, Plexiglass, Acrylite and Perspex.

i) Its monomer  is  known as Methylmethacrylate.

                      

ii) It  is a homopolymer.

iii) It  is  an addition polymer.

iv) It  is prepared by addition polymerization.

 

USES  OF PMMA

i) It is used to manufacture optical lenses, transparent domes, aircraft windows etc.

ii) It is used to prepare attractive sign boards.

11)NYLON-6

i) Its monomer is caprolactum.

       

ii) It  is a polyamide because it contains amide linkage.

                                                

iii) It  is a homopolymer.

iv) It  is  an addition polymer.

v) It  is prepared by addition polymerization.

          

USES  OF NYLON-6

It is used to manufacture tyre cords, ropes and fabrics.

12) POLYHYDROXYBUTYRATE (PHB)

(i)It  is a biodegradable polymer.

(ii)Its  monomer  is 3-Hydroxybutyric acid .

                 

(iii) It is  a polyester because it contains ester linkage.

                                  

iv) It is a homopolymer.

v) It is a  condensation polymer.

vi) It is prepared by condensation polymerization of  3-Hydroxybutyric acid .

USES  OF PHB :- It is used to manufacture films for packaging.

(13) POLYGLYCOLIC ACID (PGA)

i) Its  trade name is dextron.

ii)It is a biodegradable polymer.

(iii) It is  a polyester because it contains ester linkage.

                   

iv) Its monomer is glycolic acid.

            

v) It  is a homopolymer.

vi) It  is a condensation polymer.

vii) It is prepared by condensation polymerization of glycolic acid.

 

USES OF PGA: - It is used to prepare absorbable sutures.

(14) POLYLACTIC ACID (PLA)

i)It  is a biodegradable polymer.

ii) It is  a polyester because it contains ester linkage.

     

iii) Its monomer is Lactic acid.

   

        iv) It  is  a  homopolymer.

v) It  is  a condensation polymer.

vi) It  is prepared by condensation polymerization  of lactic acid monomer.

USES OF PLA :- To  prepare absorbable sutures.

  

1) BUNA-S or SBR or SYNTHETIC RUBBER

i) Its  contains two monomers.

a) Buta-1,3-diene

     CH₂=CH-CH=CH₂

b) Styrene.

      C₆H₅-CH=CH₂  or

    

ii) It is a copolymer.

iii) It is an addition polymer.

iv)It is prepared by addition polymerization of Butadiene and styrene by heating with sodium.

USES  OF SBR :- It is used to manufacture automobile tyres,rubber soles, water proof shoes etc.

(2) BUNA-N or NITRILE  RUBBER

i)It  consists of  two monomers.

           a) Buta-1,3-diene

           CH₂=CH-CH=CH₂

          b)  Acrylonitrile

            CH₂=CH-CN

ii) It  is  a  copolymer.

iii) It  is  an addition polymer.

iv) It  is prepared  by addition polymerization  in  the presence of  peroxide catalyst.

USES  OF  BUNA-N

It is used in making Oil seals, Fuel tanks. Hoses( water pipes) etc.

3)TERYLENE OR DACRON

(i) It is  a polyester because it contains ester linkage.

                   

iii) It is a copolymer.

iv) It  is a condensation polymer.

v) It is prepared by condensation polymerization.

USES OF DACRON

 (i)It  is used    for  making  safety belts, tyre cords, tents etc.

  (ii) It is used as glass enforcing material for safety helmets.

4) NYLON-66

i) It  is  a polyamide  as  it  contains amide linkage .

                          

ii) It contains following two monomers.

  

iii) It is a copolymer.

iv) It  is a condensation polymer.

v) It is prepared by condensation polymerization.

USES OF NYLON-66

1). Nylon 6, 6 is used in making sheets, bristles for brushes and in textile industry.

2) Socks and sweaters.

3)Cords and climbing ropes.

(5) GLYPTAL

i)It  is a polyester as it contains ester linkage.

           

ii)Its  repeating structural units are.

    

iii) It is a copolymer.

iv) It  is a condensation polymer.

v) It  is prepared by condensation polymerization  of  ethylene glycol   and phthalic acid.

      

USES  OF GLYPTAL :-It is  used to prepare paints , lacquers and building material.

(6) NOVOLAC(phenol formaldehyde resin)

The   condensation of  ortho-hydroxybenzyl alcohol or para-hydroxybenzyl  alcohol forms    a  linear polymer  known  as Novolac.

The  ortho-hydroxybenzyl alcohol and para- hydroxybenzyl are  obtained by the reaction of  phenol and formaldehyde in the presence of  an acid or base catalyst.

                    

  USE OF NOVOLAC:- It  is used in paints.

(7) BAKELITE (phenol formaldehyde resin)

The  ortho and parasubstituted phenols undergo condensation polymerization  to form a cross-linked polymer known  as Bakelite.

The  ortho and para substituted phenols (ortho-hydroxybenzyl alcohol and para- hydroxybenzyl  alcohol ) are  obtained by the reaction of  phenol and formaldehyde in the presence of  an acid or base catalyst.

USES OF BAKELITE : It is used for making combs, phonograph records, electrical switches and handles of various utensils.

MELAMINEFORMALDEHYDE

i) It is a crossed-linked polymer.

ii) Its monomers are :

iii) It is a copolymer.

iv) It is a condensation polymer.

    

 

USES OF MELAMINE FORMALDEHYDE RESIN :- It is used in the manufacture of unbreakable crockery.

                                                                     UREA FORMALDEHYDE RESIN

ii) It is a copolymer.

iii) It is a condensation polymer.

iv)It is a polyamide as it contains amide linkage.

v) Condensation polymerization leads to the formation of urea formaldehyde resin.

             

USAGE :- It is used for making unbreakable cups, plates and laminated sheet.

PHBV

i) Its full form is

ii) It  is a biodegradable polymer.

iii)It  is a polyester as it contains  ester linkage.

                       

iv) It contains two monomer units.

(a)

(b)

v) It is a copolymer.

vi) It is a condensation polymer and is formed by condensation polymerization.

USEAGE :- (i)It  is used to make capsule coat  for medicines .

                       (ii) It is used to make films for packaging.

POLY DISPERSITY INDEX (PDI)

It  is the ratio of weight average molecular mass to the number of average molecular weight.

                                     

It  gives idea for homogeneity  of the polymers.

For natural polymers.

                     PDI=1

        Hence  M_n=M_w

They are monodisprese in nature.

For synthetic polymers

                     PDI>1

        Hence  M_w>M_n

They are polydispresed in nature.

Q:-Which polymer is used to make bullet proof glasses ?(LEXAN)

Q:-Which polymer is used in bubble gum?(BUNA-S)

Q:-What is the trade name of PAN?(ORLON or ACRILON)

Q:-What is the trade name of Terylene?(DACRON)

Q:-Which polymers are used in Terrycot(TERYLENE AND COTTON)

Q:-What are NYLON-6,10 and NYLON-2-NYLON-6

Q:- Write down the structure of 

Q:- What are non-biodegradable polymers?

Ans:-The polymers which can not be decomposed by the micro-organisms  are called non-biodegradable polymers .E.g.polythene etc.

Q:- What are biodegradable polymers?

Ans:- The polymers which can be decomposed by micro-oganisms  are called biodegradable polymers.E.g.paper,wool,silk,cotton,jute etc.

Q:- What are biopolymers?

Ans:- The  polymers  which  are found  in  living  organisms  are  called  biopolymers. Most of the biomolecules are biopolymers .E.g. starch,cellulose,proteins,lipids,nucleic acids etc.

Q:- Give  the reaction of phenol and formaldehyde  to from Bakelite ?

Q:- What are polyamides?

Ans:-Polymers which have amide linkage are called polyamides. They are condensation polymers and hence prepared by condensation polymerization.E.g. Nylon-66, Nylon-6 etc.

iii) Nylon 2–nylon 6
It is a polyamide copolymer of glycine (H₂N–CH₂–COOH) and amino caproic acid [H₂N(CH₂)₅COOH] and is biodegradable. Can you write the structure of this copolymer?

Q:-What are polyesters?

Ans:-Polymers which possess ester linkage are called polyesters. They are condensation polymers and hence prepared by condensation polymerization.E.g. Dacron etc. The formation of terylene or dacron from ethylene glycol and terephthalic acid is an example of condensation polymerization.  It is manufactured by heating a mixture of ethylene glycol and terephthalic acid at 420 to 460 K in the presence of zinc acetate antimony trioxide catalyst. Dacron fibre (terylene)  is used in blending with cotton and wool fibres and also as glass reinforcing materials in safety helmets, etc.