Introdn Polymer

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PolymerPolymer: Maromolecule built-up by the linkingtogether of a large no. of small molecules

Ex. Nucleic acid, paper, bakelite,PVC

Monomer: The small molecule which combine

with each other Mer: The repeat unit

Degree of polymerisation (DP): The no. of

repeating unit(n)Degree ofpolymerisation=Molecular wt of the polymericnetwork/molecular wt of the repeating unit

Depends on degree of polymerisation polymers aretwo types

Oligo polymers:Polymer with low mol.wt

Hi h lo mer: Pol mer with hi h mol. wt



Polypropylene

mer

Monomer



Nomenclature of PolymerI. Based on the chemical structure of monomer

i)Homo polymer and ii)copolymer II. Based on the arrangement of monomer in the structu

Homo Polymer:

i)Linear, ii)branched and iii)Cross linked or 3-D polymer

Co polymer:

Linear:i) Regular, ii)Alternating, iii) block and iv)random

copolymer

Branched: Graft copolymer

Cross-linked copolymerIII. Based on atoms in the main chain

i)Homochain polymer and ii)heterochain polymer



Nomenclature-contdI)Based on the chemical nature of the

monomer units Homopolymer : Identical monomersHomopolymer : Identical monomers

(Polyethylene)(Polyethylene) Copolymer : Monomers with different chemicalCopolymer : Monomers with different chemical

structure (Buna-S: butadiene and styrene)structure (Buna-S: butadiene and styrene)II) Based on structure of polymer chainsII) Based on structure of polymer chains

(Homopolymer &Copolymer)(Homopolymer &Copolymer)

i. Linear homopolymer : - A – A – A – A –i. Linear homopolymer : - A – A – A – A –ii. Branched homopolymer : - A – A – A – A -

A

iii. Cross – linked polymer :- A – A – A – A – A – A – A – A -

- A – A – A – A – A – A – A –



Linear polymer



Branched chain polymer



Cross linked or 3-D polymer-Bakelite



Copolymers Regular Polymer : Regular

arrangement of monomerunits A&B

Alternating copolymers withregular alternating A and B units

Random copolymers withrandom sequences of monomerA and B

Block copolymers comprised

of two or more homo polymersubunits in long sequenceslinked by covalent bonds

Graft Copolymers are a

special type of branchedcopolymer in which the sidechains are structurally distinctfrom the main chain.

A-A-A-B-A-A-A-B-A-A-A-B

Regular Copolymer



Nomenclature-contd

III)III. Based on atoms in the main chain

Homochain polymer: Main chain is made up

of same species of atoms

Ex., PVC

ii)heterochain polymer: Main chain is madeup of different atoms

ex.,Nylon 6:6 (mer),



Copolymer ( Buna-S or SBR)

mer



Tacticity (Difference in Configuration)Affect their physical properties

Isotactic: Functional gpsor sidegps are all on the sameside:ex., Polypropylene

synthesised using Zielgar Nattacatalyst

Syndiotactic Arrangement of

functional groups or side gps inalternating fashion: Guttapercha-Natural rubber

Atactic: Arrangement offunctional gps or side gpsareat random around the mainchain ex., Polypropylene



Functionality Number of bonding sites in a monomer

It determines the structure of the polymer.

Three Typee

Bifunctional, trifunctional and polyfunctional11)Bifunctional monomer:Two reactive sites or bonding

sites.

Reactive gp attach side by side to each other forminglinear or straight chain molecule

Monomer units linked by covalent bonds but differentchains are held by van der Waals force

Chain movement in one direction is possible Compound with double bond, amino acid, di-ol etc.,

ex., ethylene glycol, ethylene.



Functionality -contd

2)Trifunctional monomer: Contains three active sites

Result in branched chain molecule even if it presents in

small amount with bifunctional monomerex.,dimethylol phenol

Movement of chain molecules are restricted due topresence of side chain

3) Containing more than three functional gps.ex.,trimetylol phenol

Monomers are connected to each other by covalent

bonds which results in the formation of 3D networkex., bakelite

The movement of individual molecules are prevented

b stron cross-links

T f P l i ti



Types of Polymerisation• Addition or Chain polymerisation : Polymer is formed by an

addition reaction, where many monomers bond together viarearrangement of bonds without the loss of any atom or molecule

• Monomers contains one or more double bonds which byintermolecular rearrangement make the polymer which is an exactmultiple of monomer

• Reaction is instigated by the application of heat, light, pressure ora catalyst -break the double bond.

• The polymerisation once initated cannot continue indefinitely as itbecomes difficult to sustain long chain.

• Growth reaction adds repeating units one at a time to the chain

• Ex for Homo polymerisation ; PVC



Addition or Chain polymerisation • Ex. Homo polymerisation :,Nylon-6: Involves an intramolecular

rearrangement of bonds by opening of cyclic monomer

• Ex. Copolymerization of t wo different monomer:Polybutadiene-co-styrene

mer

Condensation or Step Polymerisation



Condensation or Step Polymerisation

• Reaction between simple polar gp containing monomers

• Formation of polymer takes place by elimination ofsmall molecules like water, HCl, CH3OH, NH3 etc.,

• An intermolecular combination of monomer.

• When monomers contain three functional gps it may

give cross-linked structure molecule.• Ex.,(Nylon 6,6)

+ 2n H2O

n n

n

a n an con ensa on po ymer sa on



a n an con ensa on po ymer sa on•Chain polymerisation

•Monomer must have two bonding

sites

•Inter molecular or intramolecular Rearrangement

•Mostly results in homo chain

polymer

•Only growth reaction adds repeatingunits one at a time to the chain

•Number of units decreases steadily

throughout the reaction

•Reaction mixture contains onlymonomer and polymer- no other pdts

•Linear polymer and Thermoplastics

•Mol. Wt of polymer is exact multipleof mol.wt of monomer

•longer reaction time has little effect

on the molecular wt but gives higher

Condensation polymerisation

•Monomer must contain polar group

• Intermolecular combination ofmonomers

•Mostly results in hetero chain polymer

•All types of molecular species present

can react•Monomer disappears early in the

reaction

• All types of molecular species and by

products are present at any stage•Branched and cross-linked polymer-

thermosetting plastics

•Molecular wt is not an exact multiple o

mol.wt of monomer•Moecular mass (DP)rises steadily

throughout the reaction and hence

reaction time is essential



ClassificationClassification Based on origin:Based on origin:

Natural (Cellulose, Protein, silicone) and syntheticNatural (Cellulose, Protein, silicone) and synthetic(Bakelite)(Bakelite)

Based on StructureBased on Structure

Linear, Branched, 3-dimensional or cross linkedLinear, Branched, 3-dimensional or cross linkedBased on main chain (back bone/ skeleton)Based on main chain (back bone/ skeleton)

i) Homo chain: made up of single type of atom (ex) PEi) Homo chain: made up of single type of atom (ex) PE

ii) Hetero chain: made up of different types of atomsii) Hetero chain: made up of different types of atoms(ex)nylons(ex)nylons

Based on molecular forces (Thermal behaviour)Based on molecular forces (Thermal behaviour)

Thermoplastics, Thermosetting plastics, Fibres, ElastomersThermoplastics, Thermosetting plastics, Fibres, Elastomers

Based on method of synthesisBased on method of synthesis

Addition polymer (eg) PE, PP, PS, nylon 6.Addition polymer (eg) PE, PP, PS, nylon 6.

Condensation polymer (eg)Polyesters , nylon 6,6 Condensation polymer (eg)Polyesters , nylon 6,6

Thermo plastics and Thermosetting plasticsThermo plastics and Thermosetting plastics



Thermo plastics and Thermosetting plasticsThermo plastics and Thermosetting plasticsThermosetting Plastics

Do not soften; they burnon heating

3-D cross-linked structure

with co-valent bondCondensation polymer

Can not be reshaped

Hard, strong and brittleCannot be reclaimed

Due to strong bonds andcross links they areinsoluble in almost all org.solvents Ex.,Bakelite

Thermo plastics

Soften on heating andharden on cooling reversibly

Long-chain macromolecule

Addition polymerisation

Reshaped, reused

Soft, weak and less brittle

Reclaimed from waste

Soluble in some org.solvents

Ex., PVC

Elastomers and Fibers



Elastomers and Fibers

Elastomer: Rubber• High elastic properties

• Can be stretched to 4 to 10 times its original

length• Unstressed condition they are not in straigth

chain but in the form of coil

Fibers• Held by strong intermolecular forces like

H-bonding

• Continuous filament ex. Cellulose



Plastics

Org .materials of high mol.wt, which can be mouldedinto any desired form, when subject to pressure andheat in presence of the catalyst

Resin Basic binding material, a macro molecule (polymer),major parts of the plastics

Undergoes polymerization and condensationduring preparation (Thermosetting plastics).

Mixed with 4-10 ingredients-Compounding

of plastics



• Classification Plastics

1) Based on usageCommodity plastics

PE, PS , PP, PVC,

Engineering Plastics

Teflon (PTFE) ,PC (Lexan), Polyesters and

Polyamides (Nylon, PET)

2) Based on thermal behaviour

Thermoplsatics

Thermosetting plastics

E i i Pl i



Engineering PlasticsEngineering Plastics Used to replace conventional materials like metal, wood, glass,Used to replace conventional materials like metal, wood, glass,

ceramics etc.ceramics etc. Used to develop composite articles Used to develop composite articles

CharacteristicsCharacteristics Resistant to corrosion Resistant to corrosion

cast into any desired shape cast into any desired shape light-weight light-weight low thermal coefficient of expansion low thermal coefficient of expansion chemical inertness chemical inertness low melt.pt.low melt.pt. decorative finish decorative finish impermeable to water impermeable to water

low heat resistance low heat resistance

deformation under load,deformation under load, High abrasion resistance High abrasion resistance Dimensional stability Dimensional stability

A li ti



ApplicationsIn automobile

In defenseElectrical and electronics

Telecommunication

TextileSatellite

Computer components (table top, screen)

RobotsIn aeronautical engineering

Chemical industry

Paper Industry

Adhesives

Lubricants

Introdn Polymer

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