hari om suresh dani’s classes xii chemistry chapter no

Hari Om SURESH DANI’s CLASSES JSK

XII – CHEMISTRY – THEORY + MCQS

CHAPTER NO - 15 – INTRODUCTION TO POLYMER CHEMISTRY

(Weightage : 04 Marks) (Advance Batch Notes: YEAR - 2020)

Introduction to Polymer of 29

PART: I – INTRODUCTION

Chemistry plays a very important role in day to day life.

There are different types of branches comes under chemistry.

Polymer chemistry emerged as a separate branch of chemistry during the last several decades due

to the voluminous knowledge built up in this field and the ever increasing applications in everyday

life.

The term “Polymer” was coined in 1833 by Berzelius while performing cellulose derivative

experiments.

MEANING OF MONOMER :

The term 'monomer' originates from Greek word 'mono' meaning single or one and 'mer' meaning

part or unit.

i.e. (single unit /single part 0r one unit/one part)

DEFINITION OF MONOMERS :

A lower molecular weight molecule capable of reacting with identical or different molecules of low

molecular weight to form a polymer are called as Monomers.

OR The simple molecules which combined to form a polymers are called Monomers.

MEANING OF POLYMER :

The term 'polymer' originates from Greek word 'poly' meaning many or more and 'meros' meaning

part or unit.

i.e. (Many unit / Many part 0r More unit/More part)

DEFINITION OF POLYMERS :

Polymers are high molecular mass macromolecules (103 – 107 u) made from repeating units of monomers.

EXAMPLES:

Name Of Monomer Name of Polymer

1. Glucose Starch

2. Glucose Cellulose

3. Aminoacids Protein

4. Nucleotide Nucleic acid(DNA)/(RNA)

5. Ethene Polyethene

6. Vinylchloride Polyvinylchloride (PVC)

Hari Om SURESH DANI’S CLASSES Jsk


REPRESNTATION OF POLYMERS:

Monomer Repeating units of Monomer Representation of Polymer

1. n A –(A)– –[A]n–

2. n A + n B –(A-B)– –[A-B]n–

3. n A + n B + n C –(A-B-C)– –[A-B-C]n–

4. n CH2 = CH2

Ethene

–(CH2 – CH2)– –[ CH2 – CH2]n–

Polythene

5. n CH2 =CH – CH= CH2

Buta – 1,3 –diene

+

n CH2 =CH – CN

Acrylonitrile

–(CH2 –CH = CH–CH2–CH2–CH)–

CN

–[CH2 –CH = CH–CH2–CH2–CH]n–

CN

Buna - N

DEFINITION OF POLYMERIZATION:(PROCESS)

The process by which the simple molecules (i.e. monomers) are converted into polymers is called

polymerization.

OR

A process of synthesizing polymers from repeating units of monomers is called as polymerization.

i.e. PolymerizationMonomer Polymer

Example: Transformation of ethene to polythene.

Polymers are Inorganic (Ex. Silicones) as well as organic (Ex.Polythene).

Organic biopolymers (Ex.Starch) playing crucial role in living world.

NOTE:

All polymers are macromolecules but all macromolecules are not polymers because

macromolecules do not contain repeating units of monomers.

Example: Haemoglobin and Chlorophyll are macromolecules but are not polymer because

Haemoglobin and Chlorophyll do not contain repeating units of monomers.

PART – I – EXERCISE: IMPORTANT QUESTION – (EACH QUESTION – 2 Mark)

1. Define Monomers. Write its example.

2. Define Polymers. Write its example.

3. Define Polymerization. [ 1 M ]

4. Write the structural representation of following polymers:

a) Polythene b) Buna – N

5. Write the name of monomer used to prepare following polymers:

a) Starch b) Proteins

c) DNA d) Polyvinylchloride(PVC)



PART: II – CLASSIFICATION OF POLYMERS

Polymers are classified in a number of ways as mentioned below:

1. Classification based On Source or Origin

2. Classification based On Structure

3. Classification based On Mode Of Polymerization

4. Classification based On Intermolecular forces

5. Classification based On Type of Monomers

6. Classification based On Biodegradability

7. Classification based On growth polymerization (Not in G. text book refer NCERT )

1. CLASSIFICATION BASED ON SOURCE OR ORIGIN:

On the basis of source, polymers are classified into the following three categories:

i. Natural polymers:

The polymers obtained from nature are called natural polymers.

They are further subdivided into two types: Plant polymers and Animal polymers.

Plant Polymers Animal Polymers

These are obtained from plants. These are derived from animal sources.

For example:

Cotton : Cotton plant

Linen : Flax plant

Natural rubber : (latex)Bark of rubber trees

Jute : Vegetable fibres

Starch : Carbohydrates

Cellulose : Wood pulp

For example:

Wool : Sheep

Silk : Silkworm

Leather: Animal silk

ii. Semi-synthetic polymers:

The properties of natural polymers such as appearance, tensile strength, lustre, etc are

modified by some chemical treatment, to obtain semi-synthetic polymer.

These are also called regenerated fibres.

Example: Cellulose derivatives such as cellulose acetate rayon, cellulose nitrate, viscose

rayon, cuprammonium rayon etc

Semisynthetic polymers are used in preparation of non-inflammable photographic films,

cinema films, varnishes, etc.

iii. Synthetic polymers:

The polymers which are synthesized in the laboratories or in the industries are called

synthetic polymers.

These are also called Man made polymers.

These are further divided into three subtypes, namely fibres, synthetic rubbers and

plastics.



Example:

Fibres Synthetic rubbers Plastics

Nylon – 6 Buna – S (SBR rubber) Polythene

Nylon – 6,6 Buna – N Polyvinylchloride(PVC)

Terylene (Dacron) Neo-prene Polypropene

- Butyl rubber Teflon

- - Orlon

- - Polystyrene

- - Bakelite

2. CLASSIFICATION BASED ON STRUCTURE:

On the basis of structure, polymers are divided into three types:

i. Linear or Straight chain polymers: [1 Dimensional structure]

A polymer formed by combination of repeating units of monomers having long continuous

chains without any excess attachments (branches) are called linear polymers.

It is obtained from bifunctional monomers or alkenes.

These are well packed and therefore, have high densities, high tensile strength and high

melting points.

Example:


Nylon – 6 Buna – N (SBR rubber) Polythene(HDPE)

Nylon – 6,6 Neo-prene Polyvinylchloride(PVC)

Terylene (Dacron) - Teflon

- - Orlon

ii. Branched chain polymers: [2 Dimensional structure]

A polymer formed by combination of repeating units of monomers having long continuous

chains with small attachments (branches) are called branched chain polymers.

It is obtained from Monomer having 3 functional groups or already having side chains.

These are irregularly packed and therefore have low density, low tensile strength and low

melting points than those of linear polymers.

Example: Starch , Cellulose


- Buna - S Polythene(LDPE)

- Butyl rubber Polypropylene



iii. Crossed or Network linked polymers: [3 Dimensional structure]

A polymer formed by strong covalent bonds of repeating units of monomers and have

cross-network like structure are called Network linked polymers.

It is obtained from polyfunctional monomers.

These polymers are hard, rigid and brittle because of the network structure.

Example:


- Vulcanized rubber Bakelite

- - Melamine – formaldehyde

3. CLASSIFICATION BASED ON MODE OF POLYMERIZATION:

Polymerization is the fundamental process by which low molecular mass compounds are

converted into high molecular weight compounds by linking together of repeating structural

units with covalent bonds.

This process is illustrated below. _ _ Pr

_Low molecular mass material High molecular mass material

(Possessing reactive groups)

High temperature or essure

Or Catalyst

On the basis of Mode of polymerization, polymers are divided into three types:

i. Addition polymerization or chain growth polymerization:

Addition polymerization is a process of formation of polymers by addition of monomers

without loss of any small molecules.

The repeating unit of an addition polymer has the same elemental composition as that of

original monomer.

It is obtained from Monomer having Alkene and their derivatives.

It is also referred as vinyl polymerization, since majority of monomers are from vinyl

category. (Ex: Vinyl chloride – CH2=CH – Cl & Vinyl cyanide – CH2 = CH – CN]

Example: [


- Buna – S (SBR rubber) Polythene

- Buna – N Polyvinylchloride(PVC)

- Neo-prene Polypropene

- Butyl rubber Teflon

- - Orlon



ii. Condensation polymerization or step growth polymerization:

Condensation polymerization is a process of formation of polymers from polyfunctional

monomers with the elimination of some small molecules such as water, hydrochloric acid,

methanol, ammonia.

The polymerization occurs in step wise manner and forms dimers, tetramers.... and so on.

It is obtained from Monomer having functional group.

Example :


Nylon – 6,6 - Bakelite

Terylene - Melamine – formaldehyde

iii. Ring opening polymerization:

Ring-opening polymerization (ROP) is a form of chain-growth polymerization, in which

the terminus of a polymer chain attacks cyclic monomers to form a longer polymer.

Elemental composition of the repeating unit in the polymer resulting from ring opening

polymerization is same as that of the monomers, as in the case of addition polymerization.

It is obtained from cyclic compounds like lactams, cyclic ethers, lactones, etc. polymerize

by ring opening polymerization. Strong acid or base catalyze this reaction.

Example : Nylon – 6

caprolectum Nylon – 6

4. CLASSIFICATION BASED ON INTERMOLECULAR FORCES:

Mechanical properties of polymers such as tensile strength, toughness, elasticity differ

widely depending upon the intermolecular forces.

On the basis of intermolecular forces, polymers are divided into four types:

i. Elastomers:

The polymers that have elastic character like that of rubber are called elastomers.

Elasticity is a property by which a substance gets stretched by external force and restores

its original shape on release of that force.

A few crosslinks between the chains help the stretched polymer to retract to its original

position on removal of applied force.

Elastomers have weak van der Waals type of intermolecular forces.

https://en.wikipedia.org/wiki/Chain-growth_polymerization

https://en.wikipedia.org/wiki/Polymer

https://en.wikipedia.org/wiki/Cyclic_compound



Elastomers are soft and stretchy. They are used for making rubber bands.

Examples :


- Buna – S (SBR rubber) -

- Buna – N -

- Neo-prene -

- Butyl rubber -

Vulcanized rubber

ii. Fibres:

Fibres are the thread-forming solids which possess high tensile strength and are used in

textile industries.

The fibres possess high tensile strength which is a property to have resistance to breaking

under tension.

It is crystalline in nature.

The strong intermolecular forces between the chains (which lead to close packing of

chains) are hydrogen bonds, dipole – dipole interaction etc.

Examples :


Nylon – 6 (Polyamide) - -

Nylon – 6,6 (Polyamide) - -

Terylene (Polyester) - -

- -

-

iii. Thermoplastic polymers :

Thermoplastic polymers are the linear or slightly branched long chain molecules

capable of softening on heating and hardening on cooling.

It is linear or slightly branched in nature.

It can be remould and recycled or reused.

Polymers possess moderately strong intermolecular forces that are intermediate

between elastomers and fibres.

They are formed by Addition polymerization.

Examples:


- - Polythene

- - Polystyrene

- - Polyvinylchloride

- - Polypropene

- - Polyurethanes



iv. Thermosetting polymers :

Thermosetting polymers are cross linked or heavily branched molecules, which on

heating undergo extensive cross linking in moulds and again become infusible (not able

to be melted).

It is cross linked or heavily branched molecules.

It cannot be remould and recycled or reused.

Polymers possess extensive cross linking by covalent bonds formed in the moulds during

hardening/setting process while hot.

They are formed by Condensation polymerization.

Examples:


- - Bakelite

- - Melamine - formaldehyde

- - Urea- formaldehyde

5. CLASSIFICATION BASED ON TYPE OF MONOMERS:

On the basis of type of monomers polymers are divided into two types:

i. Homopolymers:(Homo – Same type )

The polymers which have only one type of repeating unit of monomer are called

homopolymers.

They are formed from a single monomer or in some cases the repeating unit is formed by

condensation of two distinct monomers.

Example :


Nylon – 6 Neo-prene Polythene

- - Polystyrene

- - Polyvinylchloride

- - Polypropene

- - Polyacrylonitrile(PAN) (Orlon)

Teflon

ii. Heteropolymers:(Hetro – differen type )/ Copolymers:

The polymers which have two or more types of repeating units of monomer are called

copolymer.

The different monomer units are randomly sequenced in the copolymer.

Example :


Nylon – 6,6 Buna - S Bakelite

Terylene (Dacron) Buna - N Melamine - formaldehyde

- Butylrubber Urea- formaldehyde

- - ABS - plastic



6. CLASSIFICATION BASED ON BIODEGRADABILITY :

On the basis of type of biodegrability polymers are divided into two types:

i. Bio-degradable polymers:

The polymers which are degraded by micro-organisms within a suitable period so that

the polymers and their degraded products do not cause any serious effects on the

environment are called biodegradable polymers.

Examples : PHBV , Dextron , Nylon–2 –Nylon–6

ii. Non-biodegradable polymers:

The polymers which are not degraded by micro-organisms called non-biodegradable

polymers.

Examples : Polythene, PVC , Orlon , Bakelite etc.

PART – II – EXERCISE: IMPORTANT QUESTION – (EACH QUESTION – 2 Mark)

1. What are the different ways of classification of polymers?

2. How are polymers classified on the basis of source?

3. How are polymers classified on the basis of structure? [ 3 M ]

4. How are polymers classified on the basis of mode of polymerization?

5. How are polymers classified on the basis of intermolecular forces? [ 4 M ]

6. How are polymers classified on the basis of type of monomers?

7. How are polymers classified on the basis of biodegradability?

8. Classify the following as linear, branched or cross linked polymers.

i. Bakelite ii. Starch iii. Polythene iv. Nylon

9. Classify the polymers given below as addition and condensation polymers.

i. PVC ii. Polythene iii. Polyester iv. Polyacrylonitrile

10. Distinguish between Natural polymers and Synthetic polymers.

11. Distinguish between thermoplastic polymers and thermosetting polymers.

NOTE: On the basis of intermolecular forces the priority order is (Strong to Weak)

Fibres > Thermoplastic > Thermosetting



PART: III – MECHANISM OF POLYMERIZATION:

NOTE: Only for Information purpose no need to remember.

The mechanism of polymerization is based on type of processes.

There are three types of polymerization processes,

1. Addition 2. Condensation 3. Ring opening chain

In Addition polymerization three types of mechanism

a. Free radical b. Anionic c. Cationic

(As per syllabus Free radical polymerization have to study)

FREE RADICAL POLYMERIZATION :

Free radical mechanism is most common in addition polymerization.

It is also called chain reaction which involves three distinct steps:

Step – 1 - Chain initiation:

1. The chain reaction is initiated by a free radical. An initiator (catalyst) such as benzoyl

peroxide, acetyl peroxide, tert-butyl peroxide, etc. can be used to produce free radical.



2. The free radical (say .CH3/

.R) so formed attaches itself to the olefin (vinyl monomer) and

produces a new radical.

Step – 2 - Chain propagation:

The new radical formed in the initiation step reacts with another molecule of vinyl monomer,

forming another still bigger sized radical.

Step – 3 - Chain termination:

The chain propagating step can be stopped by any of the following methods:

a. The supply of monomer is stopped

b. Impurity such as oxygen is added

c. Combination of two growing chain radicals.

PART – III – EXERCISE: IMPORTANT QUESTION – (3 Mark)

Explain in detail free radical mechanism involved during preparation of addition polymer.



PART: IV – SOME IMPORTANT POLYMERS:

1. RUBBER : Elastomers are popularly known as rubbers.

For example, balloons, shoe soles, tyres, surgeon's gloves, garden hose, etc. are made from

elastomeric material or rubber.

Rubbers are of three types :

a. Natural Rubber

b. Vulcanized Rubber

c. Synthetic Rubber

a. Natural Rubber :

Natural rubber is a high molecular mass cis-1,4-polyisoprene of linear polymer of isoprene.

It is obtained from latex which is a colloidal solution of rubber particle in water.

Its molecular mass varies from 130, 000 u to 340, 000 u (that is number of monomer units

varies from 2000 to 5000).

Monomer of natural rubber is isoprene (2-methyl - 1, 3-butadiene).

Reaction involved in formation of natural rubber by the process of addition polymerization

is as follows.

Representation of Natural rubber :

(cis-1,4-polyisoprene)

Properties of Natural Rubber:

Polyisoprene molecule has cis configuration of the C = C double bond.

It consists of various chains held together by weak van der Waals forces and has coiled

structure.

It can be stretched like a spring and exhibits elastic property.



b. Vulcanized Rubber :

To improve the physical properties of natural rubber, a process of vulcanization is carried

out.

Charles Goodyear, invented a process of vulcanization.

Definition of Vulcanization: The process by which a network of cross links is introduced into

an elastomers is called vulcanization.

Explanation :

1. Natural rubber when mixed with 3 to 5% sulphur and heated at 100-150 C, forms cross

linking of cis-1,4-polypropene chains through disulphide bonds, (SS). Crosslinking

prevents the polymer from being torn when it is stretched.

2. The profound effect of vulcanization enhances the properties like tensile strength,

stiffness, elasticity, toughness; etc. of natural rubber.

3. By controlling the amount of sulphur used in vulcanization, the physical properties of

rubber can be altered to suit the requirements.

4. Example :

Neo prene is vulcanized with MgO and Buna –S vulcanized with sulphur.

NOTE:

1 to 3% sulphur is used for low sulphur rubber. It is used in rubber bands.

3 to 10% sulphur is a little harder. It is used in tyres.

20 to 30% sulphur is hard rubber. It is used to make heavy vehicle tyres.

40 to 45 % sulphur is non-elastic hard material known as ebonite is obtained.

c. Synthetic Rubber :

The rubber which is synthesized in the laboratories or in the industries is called synthetic

rubber.

Example: Buna – S, Buna – N, Neo prene, Butyl rubber etc.

1. Buna – S :

It is also known as Styrene butadiene rubber. i.e SBR rubber.

Buna-S is an elastomer which is a copolymer of styrene with butadiene.

The copolymer is usually obtained from 75 parts of butadiene and 25 parts of styrene

subjected to addition polymerization by the action of sodium.

Reaction :



Buna-S is superior to natural rubber with regard to mechanical strength and has

abrasion resistance.

It is used in Inner tubes for tyres, motors, bubble gums etc.

2. Neoprene rubber :

Neoprene or polychloroprene is formed by the free radical addition polymerization

of chloroprene.

Chloroprene polymerizes rapidly in presence of oxygen.

It is a homopolymer, synthetic rubber.

Reaction : (Neoprene)

Vulcanization of neoprene takes place in presence of magnesium oxide and undergo

condensation polymerization.

The reactions involved can be represented as follows:

Neoprene is particularly resistant to petroleum, vegetable oils, light as well as heat.

Neoprene is used in making hose pipes for transport of gasoline and making gaskets.

It is used for manufacturing insulator cable, jackets, belts for power transmission and

conveying.

2. POLYTHENE : Polythene is the simplest and most commonly used hydrocarbon thermoplastic and has

following structure.

[-CH2 - CH2-]n

The IUPAC name of polyethylene is polythene.

Polythene is of two kinds, namely low density polythene (LDP) and high density polythene

(HDP).



a. Low density polythene(LDP):

Reaction :

2Traces of O

2 2 2 2peroxide at_350 - 370K 1000-2000 atm

n CH = CH [CH CH ]

LDP

n

LDP is obtained by polymerization of ethylene under high pressure (1000 - 2000 atm)

and temperature (350 - 570 K) in presence of traces of O2 or peroxide as initiator.

The mechanism of this reaction involves free radical addition and H-atom abstraction.

The latter results in branching. As a result the chains are loosely held and the polymer

has low density.

In the H-atom abstraction, process involved in formation of LDP; the terminal carbon

radical abstracts H-atom from an internal carbon atom in the form of an internal carbon

radical. Termination step in addition polymerization gives rise to branching of these

internal carbons.

(Note: No need to remember the upper mechanism only for information)

Properties of LDP:

LDP films are extremely flexible, but tough, chemically inert and moisture resistant.

It is poor conductor of electricity with melting point 1100C.

Uses of LDP:

LDP is mainly used in preparation of pipes for agriculture, irrigation, domestic water line

connections as well as insulation to electric cables.

It is also used in submarine cable insulation.

It is used in producing extruded films, sheets, mainly for packaging and household uses

like in preparation of squeeze bottles, attractive containers etc.

b. High density polyethylene (HDP):

Reaction:

333 K - 343 K

2 2 2 2 6 - 7 atm, Zeigler-Natta catalyst

n CH = CH [CH CH ]

HDP

n

It is essentially a linear polymer with high density due to close packing.



HDP is obtained by polymerization of ethene in presence of Zieglar-Natta catalyst which

is a combination of triethyl aluminium with titanium tetrachloride at a temperature of

333K to 343K and a pressure of 6-7 atm.

Properties of HDP:

HDP is crystalline, melting point in the range of 144 - 1500C.

It is much stiffer than LDP and has high tensile strength and hardness.

It is more resistant to chemicals than LDP.

It is a translucent polymer.

Uses of HDP:

HDP is used in manufacture of toys and other household articles like buckets, dustbins,

bottles, pipes etc.

It is used to prepare laboratory wares and other objects where high tensile strength and

stiffness is required.

3. TEFLON :

Chemically teflon is polytetrafluoroethylene.

The monomer used in preparation of teflon is tetrafluoroethylene, (CF2 = CF2) which is a

gas at room temperature.

Tetrafluoroethylene is polymerized by using free radical initiators such as hydrogen

peroxide or ammonium persulphate at high pressure.

Reaction :

Polymerization

2 2 2 2Peroxiden CF = CF [CF CF ]

Tetrafluoroethene Polytetrafluoroethene(Teflon)

n

Properties of Teflon:

Telflon is tough, chemically inert and resistant to heat and attack by corrosive reagents.

C - F bond is very difficult to break and remains unaffected by corrosive alkali, organic

solvents.

Uses of Teflon :

Telflon is used in making non-stick cookware, oil seals, gaskets, etc.



4. POLYACRYLONITRILE :

Polyacrylonitrile is prepared by addition polymerization of acrylonitrile by using peroxide

initiator.

The commercial name of PAN is Orlon or Acrilan.

Reaction:

Polymerization

2 2Peroxiden CH = CH CN [CH CH]

CN

Acrylonitrile Polyacrylonitrile

n

Properties of Polyacrylonitrile:

PAN has properties involving low density, thermal stability, high strength and modulus of

elasticity.

Uses of Polyacrylonitrile:

It is used as an artificial wool in making blankets, sweaters, bathing suits, etc.

It is used for making synthetic carpets.

5. POLYAMIDE POLYMERS :

Polyamide polymers are generally known as nylons.

Nylon is the generic name of the synthetic linear polyamides obtained by the condensation

polymerization between carboxylic acids and diamines, the self-condensation of an amino

acid or by the ring opening polymerization of lactams.

Polyamides contain - CO - NH - groups as the inter unit linkages.

Two important polyamide polymers are nylon-6 and nylon-6,6.

a. Nylon – 6 :

When epsilon (ε)-caprolactam is heated with water at high temperature it undergoes ring

opening polymerization to give the polyamide polymer called nylon-6.

Reaction:



Note: It is also obtained by heating -Caprolactum at a high temperature (533 K) in an inert

(N2) atmosphere.

The name nylon-6 is given on the basis of six carbon atoms present in the monomer unit.

It is also known as Perlon – L.

Properties of Nylon – 6:

Nylons are crystalline polymers and take up bright colours.

They do not dissolve in hydrocarbon solvent.

They show resistance to dilute acids and bases.

They have good tensile strength.

Uses of Nylon – 6:

It is used for manufacture of tyre cords, fabrics, fish nets, brushes and ropes.

b. Nylon – 6,6:

The monomers adipic acid and hexamethylendiamine on mixing forms nylon salt, which

upon condensation polymerization under conditions of high temperature and pressure

give the polyamide fibre nylon-6,6.

Reaction:



The numerals 6,6 in the name of this polymer stand for the number of carbon atoms in

the two bifunctional monomers, namely, adipic acid and hexamethylenediamine.

Properties of Nylon-6,6:

Nylon 6,6 is high molecular mass (12000-50000 u) linear condensation polymer.

It possesses high tensile strength.

It does not soak in water.

Uses of Nylon-6,6:

It is used for making sheets, bristles for brushes, surgical sutures, textile fabrics, etc.

6. POLYESTER POLYMERS:

The polyester polymers have ester linkage joining the repeating units.

Polyester is the generic name of the synthetic polyester obtained by the condensation

polymerization between carboxylic acids and glycols.

Polyesters contain - CO - O - groups as the inter unit linkages.

Commercially the most important polyester fibre is 'terylene' (also called dacron) and

Polyethyleneterephthalate.(PET)

a. Terylene (Dacron):

It is obtained by condensation polymerization of ethylene glycol and terephthalic acid in

presence of catalyst at high temperature.

Reaction :

Properties of Terylene:

Terylene has relatively high melting point (2650C) and is resistant to heat, crease,

chemicals, light, moths, bacteria, and water.



Uses of Terylene:

It is used in the manufacture of wash and wear fabrics.

It is blended with cotton to form terrycot and with wool to form terrywool. This increases

their resistance to wear and tear.

It is used in preparation of fishing nets, ropes, trousers, magnetic tape recorders, tyres

and also used as glass reinforcing materials in safety helmets.

b. Polyethylene terephthalate:(PET)

PET is the most common thermoplastic which is another trade name of the polyester

polyethyleneterephthalate.

It is used for making many articles like bottles, jams packaging containers.

NOTE:

When it is being used as a fibre to make clothes, it is often just called polyester. It may

sometimes be known by a brand name like Terylene. When it is being used to make

bottles, for example, it is usually called PET.

c. Polycarbonate polymers:

Polycarbonates are also a kind of polyester polymers.

These are high melting thermosetting resins.

Polycarbonate is mainly used for electronic applications, telecommunication, optics,

CDs etc.

7. PHENOL - FORMALDEHYDE AND RELATED POLYMERS :

a. Bakelite:

Bakelite, the thermosetting polymer obtained from reaction of phenol and formaldehyde

is the oldest synthetic polymer.

Phenol and formaldehyde react in presence of acid or base catalyst to form

thermosetting/moulding powder (novolac) in two stages.

In the third stage, various articles are shaped from novolac by putting it in appropriate

moulds and heating at high temperature (1380C to 1760C) and at high pressure.

During the third stage of thermosetting in the moulds, many crosslinks are formed

which results in formation of rigid polymeric material, called Bakelite.



Reaction:

Stage 3:

CH2O + CH

2O + CH

2O

- nH2O



Properties of Bakelite:

It is insoluble and infusible and has high tensile strength.

It can also serve as substitute for glass.

Uses of Bakelite:

Low degree polymerization gives soft Bakelite which are used for making glue for binding

laminated wooden planks and in varnishes.

High degree polymerization gives hard Bakelite which are used in the making of electrical

switches, plugs, fountain pens, phonograph records, handles of cooker, frying pans,

combs, telephone instrument , kitchenware, electric insulators.

NOTE:

In 2nd stage the linear polymer formed is Novolac polymer is used in paints.

Novolac is a linear chain copolymer of Phenol & Formaldehyde.



b. Melamine-formaldehyde polymer :

Melamine and formaldehyde undergo condensation polymerisation to give cross linked

melamine formaldehyde.

Reaction:

Uses of melamine - formaldehyde resin:

Decorative table tops like formica and plastic dinner-ware are made from heat and

moisture resistant thermosetting plastic called melamine - formaldehyde resin.

8. VISCOSE RAYON :

Viscose rayon is a semisynthetic fibre which is regenerated cellulose.

Cellulose in the form of wood pulp is transformed into viscose rayon.

Cellulose is a linear polymer of glucose units and has molecular formula (C6H10O5)n.

Cellulose in the form of wood pulp is treated with concentrated NaOH solution to get fluffy

alkali cellulose.

It is then converted to xanthate by treating with carbon disulphide.

On mixing with dilute NaOH it gives viscose solution which is extruded through

Spinnerates of spining machine into acid bath when regenerated cellulose fibres

precipitate.

Reaction:



PART – IV – EXERCISE: IMPORTANT QUESTION – (EACH QUESTION – 2 Mark)

1. What is rubber? Mention its types.

2. Define Natural rubber. Name the monomer used to prepare Natural rubber.

3. Write the structure of Natural rubber along with name and their structure of their

monomers.

4. Define Vulcanization Write the examples of vulcanization of rubber.

5. Define Synthetic rubber. Write the examples of it.

6. Arrange the following polymers in increasing order of their intermolecular forces:

i. Nylon-6 6, Buna-S, Polythene ii. Nylon-6, Neoprene, Polyvinyl chloride

7. Write the reaction of Following polymers:

i. Buna – S ii. Neoprene

8. How is Low density polythene prepared?

9. How is High density polythene prepared?

10. How is Teflon prepared?

11. How is Polyacrilonitrile prepared?

12. How is Nylon – 6 prepared?

13. How is Nylon – 6,6 prepared?

14. How is Terylene(Dacron) prepared?

15. How is Novolac prepared?

16. How is Bakelite prepared?

17. How is Melamine-formaldehyde prepared?

18. How is Viscose rayon prepared?

19. Write uses of following polymers:


i. LDP ii. HDP

i. Teflon ii. Polyacrilonitrile

i. Nylon-6 ii. Nylon-6,6

i. Terylene ii. Novolac

i. Bakelite ii. Melamine-formaldehyde polymer

20. Write the name and chemical structure of monomers used in preparation of Polymers:


i. LDP ii. HDP

i. Teflon ii. Polyacrilonitrile

i. Nylon-6 ii. Nylon-6,6

i. Terylene ii. Novolac

i. Bakelite ii. Melamine-formaldehyde polymer



PART: V – MOLECULAR MASS AND DEGREE OF POLYMERIZATION OF POLYMERS:

a. Molecular mass of polymers:

A polymer is usually a complex mixture of molecules of different molecular masses.

Molecular mass of a polymer is an average of the molecular masses of constituent molecules.

i.e average of the molecular mass (molecular weight) = 𝑻𝒐𝒕𝒂𝒍 𝒘𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒎𝒐𝒍𝒆𝒄𝒖𝒍𝒆𝒔

𝒏𝒖𝒎𝒃𝒆𝒓 𝒐𝒇 𝒎𝒐𝒍𝒆𝒄𝒖𝒍𝒆𝒔

Molecular mass of polymer depends upon the degree of polymerization (DP).

Most of the mechanical properties of polymers depend upon their molecular mass.

Low molecular mass polymers are liable to be brittle and have low mechanical strength.

If a polymer is allowed to attain very high molecular mass it becomes tough and unmanageable.

A polymer must possess a molecular mass more than certain minimum value in order to exhibit

the properties needed for a particular application.

This minimum molecular mass corresponds to the critical degree of polymerization, But the

polymerization process has to be controlled after certain stage.

For polymers containing hydrogen bonding the critical degree of polymerization is lower than

those containing weak intermolecular forces.

Example: 1

The critical degree of polymerization is low for nylon 6 while high for polythene. Explain.

Solution :

Nylon 6 is a polyamide polymer, and has strong intermolecular hydrogen bonding as inter

molecular forces.

On the other hand polythene chains have only weak van der Waals forces as intermolecular

interaction, Because of the stronger intermolecular forces the critical DP is lower for nylon 6

than polythene.

b. Degree Of Polymerization Of Polymers:

Degree of Polymerization Of Polymers (DP) is the number of monomer units in a polymer molecule.

(Mw)



Example: 1

Calculate the degree of polymerization of Teflon, if molecular mass of Teflon is 120,000 and

molecular weight of Tetrafluoroethene is 100.

Data:

Molecular mass of polymer (teflon) (Mn) = 120,000

Molecular weight of Tetrafluoroethene (Mw) = 100.

Solution:

Degree of polymerization = 120000

100 = 1200

PART – V – EXERCISE: IMPORTANT QUESTION – (EACH QUESTION – 1 Mark)

1. What is molecular mass of Polymer?

2. What is Degree of polymerization?

PART: VI – BIODEGRADABLE POLYMERS:

The polymers which are degraded by micro-organisms within a suitable period so that the

polymers and their degraded products do not cause any serious effects on the environment are

called biodegradable polymers.

Aliphatic polyesters and polyamides with large proportion of polar linkages are one of the

important classes of biodegradable polymers.

Examples:

Aliphatic polyester polymer Aliphatic polyamide polymer

PHBV & Dextron Nylon – 2 – Nylon – 6

1. Reaction of PHBV: (poly - hydroxy butyrate - co - - hydroxy valerate)

PHBV is a copolymer of two bifunctional - hydroxy carboxylic acids, namely,- hydroxybutyric acid

(3 - hydroxybutanoic acid) and - hydroxyvaleric acid (3 - hydroxypentanoic acid).



2. Reaction of Nylon 2 - nylon – 6:

Nylon 2 – nylon – 6 is a polyamide copolymer of two amino acids, namely, glycine and - amino

caproic acid. It is a biodegradable polymer.

PART – VI – EXERCISE: IMPORTANT QUESTION – (EACH QUESTION – 2 Mark)

1. How PHBV polymer is prepared?

2. How Nylon-2-Nylon-6 polymer prepared?

3. Write the name and chemical structure of monomer used to prepare PHBV polymer.

4. Write the name and chemical structure of monomer used to prepare Nylon-2-Nylon-6 polymer.

NOTE:

Historically, the term Resin has been applied to a group of substances obtained as gums from trees

or manufactured synthetically.

Definition of Resin is a solid or highly viscous substance of plant or synthetic origin that is

typically convertible into rigid macromolecules called as Polymers and the process is known as

curing.

(Curing is a chemical process employed in polymer chemistry and process engineering that

produces the toughening or hardening of a polymer material by cross-linking of polymer chains)

Resins are usually mixtures of organic compounds.

Question in Textbook:

What are synthetic resins? Name some natural and synthetic resins.

Synthetic resins are industrially produced resins, typically viscous substances that convert into

rigid polymers by the process of curing.

Synthetic resins are polymeric materials, which are better known as plastics. (Thermo plastic and

Thermosetting resins)

Example : Natural resins : Natural Rubber ,

Synthetic resins : Polythene , Bakelite

https://en.wikipedia.org/wiki/Viscosity

https://en.wikipedia.org/wiki/Organic_compound

https://en.wikipedia.org/wiki/Resin

https://en.wikipedia.org/wiki/Viscosity

https://en.wikipedia.org/wiki/Polymer

https://en.wikipedia.org/wiki/Curing_(chemistry)

https://science.jrank.org/pages/5324/Plastics.html



PART: VII – COMMERCIALLY IMPORTANT POLYMERS:



PREVIOUS YEAR BOARD QUESTION: (MARCH 2013 to MARCH 2020)

(1) Write the chemical reaction to prepare novolac polymer. (March 2013)

(2) Explain the following terms:

(a) Homopolymers (b) Elastomers (March 2013)

(3) How are polymers classified on the basis of polymerisation process? (Oct. 2013)

(4) Write the strutcure of melamine. (Oct. 2013)

(5) What are thermoplastic polymers? (March 2014)

(6) Write names and chemical formulae of monomers used in preparing Buna-S. (March 2014)

(7) How is Nylon 6, 6 prepared? Write any ‘two’ uses of terylene. (Oct. 2014)

(8) Explain with examples, branched and linear polymers.(March 2015)

(9) What are biodegradable polymers and non-biodegradable polymers?

Write ‘one example’ of each. (March 2015)

(10) Write the reactions involved in the preparation of –

(a) Teflon (b) Orlon (c) PVC (Oct. 2015)

(11) Write the reaction for the preparation of Nylon-6. (March 2016)

(12) How are polythene and neoprene prepared? (March 2016)

(13) Write the formulae of the raw materials used for preparation of –

(a) Buna-S (b) Dextron (July 2016)

(14) How are the following polymers prepared?

(a) Orlon (b) Teflon (July 2016)

(15) Explain the following terms :

(a) Homopolymers (b) Elastomers (March 2017)

(16) How is nylon 6,6 prepared? (March 2017)

(17) How is Terylene prepared? (July 2017)

(18) Explain the preparation and uses of nylon-2-nylon-6.(March 2018)

(19) What is Elastomers? (July 2018)

Distinguish between Thermoplastic and Thermosetting polymer (July 2018)

(20) Write chemical reactions to prepare the following polymers –

(a) Teflon (b) Nylon – 6 (c) Dextron (March – 2019)

(21) Write the reactions for the preparation of polymer by using the following monomers:

(a) Vinyl chloride (b) Tetrafluoroethene (July – 2019)

(22) Define homopolymer. (July – 2019)

(23) Define Non-biodegradable polymer. Write the reaction involved in Terylene.(March 2020)

hari om suresh dani’s classes xii chemistry chapter no

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