Polymers Unit III

1

ENGINEERING CHEMISTRY UNIT-III by SUDHAKAR REDDY

UNIT-III

POLYMERS DEFINITION: Polymers are the giant molecules that are built by linking together a large number

of small particles.

Depending upon the structure, a polymer may be linear (or) branched.

Ex. – CH2 – CH2 – CH2--Si – O – Si – O – Si

Polyethylene |

Linear CH2- Si – O – Si – O –

Branched silicon resin

Depending upon the type of monomer, they may be homo polymer (made up of same monomer)

or co-polymer (made up of different monomers).

Ex. – CH2 – CH2 – n

Homo polymer

Polyethylene TYPES OF POLYMERISATION:

Basically there are two types of polymerization. They are

(i) Additive (or) Chain growth polymerization.

(ii) Condensation (or) Step growth polymerization.

ADDITIVE (OR) CHAIN GROWTH POLYMERISATION:

This type of reactions attains a product which is exactly multiple of the original mono meric

molecule. Such mono meric molecules usually have a double bond. The additive polymerization

reactions are initiated by light (or) heat (or) catalyst.

MECHANISM:

This mechanism involves three steps.

(a) Initiation

(b) Propagation

(c) Termination

INITIATION: Homo lytic cleavage of initiator leads to the foundation of free radicals

R-O-O-R Heat/hυ 2R∗ + O2

PROPAGATION: The readily found radical combines with ethylene, causing opening of double

bond and yielding another highly reactive radical. This combines with another ethylene

molecule and this process goes on till a very long chain -CH2- is built.

R∗ + CH2 = CH2 R-CH2 − 𝐶𝐻2∗

2


R-CH2 − 𝐶𝐻2∗+ CH2 = CH2 R-CH2 − CH2 − CH2 − 𝐶𝐻2

∗

TERMINATION: The reaction is terminated by the recombination of final free radicals.

𝑅I-(CH2 − CH2)n-1-CH2 − 𝐶𝐻2∗ + 𝑅II-(CH2 − CH2)m-1-CH2 − 𝐶𝐻2

∗ 𝑅I-(CH2 −

CH2)m+n-𝑅II

Here ‘n’ and ‘m’ gives the total number of mono meric molecules combined to give polymer.

CONDENSATION (OR) STEP GROWTH POLYMERISATION:

This is a reaction occurring between simple polymer group containing monomers with the

foundation of polymers and elimination of small molecules like H2O, HCl etc.

MECHANISM:

Condensation polymerization involves combination of any two monomers to give dimmers

which in turn combine to give tetramer.

It finally grows into a polymer in a step wise manner.

Molecular weight of the polymer is determined by the number of reacting functional groups

present on the monomer.

Mono functional monomer gives only low molecular weight product. Bi and Poly functional

monomers give high molecular weight condensation polymer.

PLASTICS :

Plastics are the organic material of high molecular weight and which can be molded to the

desired from when subjected to heat and pressure in the presence of catalyst. The properties

are low thermal and electrical conductivities, easy to fabricate, low specific gravity etc,.

Plastics are generally used for making automobiles parts, telephones, electrical instruments,

optical instruments. Plastics having high wear resistance properties can be used for making

gears, bearings etc,.

MERITS:

(i) They have good shock absorption capacity compared with steel.

(ii) Plastics are chemically inert.

(iii) Plastics have high corrosion resistance when compared to metals.

3


(iv) Plastics can be made according to the order like hard, soft, rigid, tough, brittle, malleable etc,. (v) Fabrication of plastics into desired shape and size is cheap.

(vi) Plastics are dimensionally stable.

(vii) Plastics doesn`t absorb water.

(viii) Thermal co-efficient of expansion of plastics is low.

(ix) Plastics are light in weight having specific gravity from 1 to 2, 4. DEMERITS:

(i) Plastics are soft.

(ii) Plastics have poor ductility.

(iii) Resistance to heat is less.

(iv) Cost of plastics is high.

(v) Plastics can deform under load.

Resins are the basic binding materials which form a major part of plastics. Resins and plastics

are used as anonymous.

CLASSIFICATION OF PLASTICS :

Plastics (or) Resins are classified into two types. They are

(i) Thermo plastic resin

(ii) Thermo set resin

THERMO PLASTIC RESIN THERMO SET RESIN

(i) They are processed by addition polymerization.

(i) These are processed by condensation Polymerization.

(ii) Softness on heating and retaining the same on cooling.

(ii) These are infusible and insoluble mass on heating i.e., heat resistance.

(iii) They are long chain linear polymers without any branched (or) cross linked chain.

(iii) They are branched (or) cross linked polymer.

(iv) On repeated chain heating and cooling, there is no change in chemical nature.

(iv) Some sort of chemical change occurs on heating.

(v) These plastics undergo purely physical process.

(v) These plastics undergo physical as well as Chemical process.

(vi) Water thermo plastics can be recovered E.g.: Teflon, PVC etc,.

(vi) Waste thermo set cannot be recovered E.g.: Bakelite, Nylon, and Polyester.

4


COMPOUNDING OF PLASTICS:

Compounding of plastics may be defined as the mixing of different materials like plasticizers,

fillers of extenders, lubricants, dyes and pigments to the thermoplastic and thermosetting

plastics to increase their useful properties like strength, toughness etc,.

Many plastics are virtually useless along but are converted into highly serviceable products by

combining them with a variety of additives, stabilizers, by the compounding process. The exact

formulation will depend upon the specific application requirement. The different additives

impart different physical properties which are used to improve the performance of the plastic

materials. Additives are widely used for thermoplastics, thermosets and elasteromers like

phenolic (or) amino resins are useless alone but by the addition of fillers, resins etc., they give a

reversible products. Some of the compounding materials are stabilizers, plasticizers, fillers,

colorants (or) pigments, lubricants and accelerators.

Some of the ingredients used in compounding of plastics are

(1) Plasticizers

(2) Fillers (or) extenders

(3) Dyes and pigments

(4) Lubricants.

PLASTICIZERS:

Plasticizers are substances added to enhance the plasticity of the material and to reduce the

cracking on the surface. Plasticizers are added to increase flexibility and toughness. Plasticizers

also increase the flow property of the plastics. Because of their addition, there is neutralization

of part of the inter molecular forces of attraction between the macro molecules of resin. Hence

greater freedom of movement between the polymeric macro molecules. There by increases the

flexibility and plasticity of the compounded material. Because of the reduction in the inter

molecular forces there is decrease in chemical resistance.

E.g.: Vegetable oil, Camphor, Castor oil, esters etc.,

FILLERS (OR) EXTENDERS:

Fillers are generally added to thermoset plastics to increase elasticity and crack resistance.

Fillers improve

(a) Thermal stability

(b) Tensile strength

(c) Non combustibility

(d) Water resistance

(e) Electrical insulation properties

(f) External appearance.

E.g.: Asbestos, Mica, Cotton, Carbon black, Graphite etc.,

5


DYES AND PIGMENTS:

These are added to impart the desired color to the plastics and give decorative effect.

Plastics are colored by adding soluble dyes and inorganic and organic pigments that are

dispersed in the plastic during processing.

Pigments are insoluble colored materials.

E.g.: Ferro cyanide, Chromates, Sulphides, Oxides, Silicates etc.

Dyes like Azo compounds –Anthra Quinone, Xanthenes etc.,

The organic dyes can be used to give transparent colors to polymers.

If opaque material is required, the mixture of organic dye and Titanium dioxide is used.

LUBRICANTS:

Lubricants are used to make the molding of plastic easier and to impart shiny finish to the

products.

Lubricants prevent the plastic material from sticking to the fabricating equipment.

E.g.: Waxes, Oils, Stearates, Soaps etc.,

The main objective of compounding is to improve the properties of the basic resin, such that the

fabrication is made easy.

MOULDING OF PLASTICS(FABRICATION OF PLASTICS):

Moulding of plastics comprises of forming and article to the desired shape by application of heat

and pressure to the moulding compounds in a suitable mould and hardening the material in the

mould. The method of moulding depends upon the type of resins used.

Fabrication of plastics is broadly classified into six types.

(1) Compress in moulding

(2) Injection moulding

(3) Transfer moulding

(4) Extrusion moulding

(5) Casting

(6) Blowing

COMPRESSION MOULDING:

This method is applied to both thermo plastic and thermo setting resins. The pre determined

quality of plastic ingredients in proper properties are filled between the two half pieces of

mould which are capable of being moved relative to each other, heat and pressure are then

applied according to specifications .The containers filled with fluidized plastic. Two halves are

6


closed very slowly. Finally curing is done either by heating or cooling. After curing the moulded

article is taken out by opening the mould parts.

INJECTION MOULDING:

This is mainly applicable to thermo plastic resins. The moulding plastic material is fed into a

heated cylinder from where it is injected at a controlled rate into the tightly locked mould by

means of a screw arrangement or by a piston plunger. The mould is kept cold to allow the

plastic to cure and become rigid. When the materials have been cured sufficiently, half of the

mould is opened to allow the injection of the finished article without any deformations. Heating

is done by oil (or) electricity.

TRANSFER MOULDING:

This uses the principle of injection for thermo set materials.

The moulding powder is fed into a heated chamber, which is maintained at a minimum

temperature where the moulding powder just begins to become plastic. The plastic material is

injected through an orifice into the mould working at high pressure. Because of the friction

developed at orifice, the temperature of the material at the time of injection from the orifice

becomes liquid. As a result the plastic material moves quickly into the mould which is being

heated up to the curing for setting. The moulded article is then ejected mechanically.

7


EXTRUSION MOULDING:

This process is useful in the preparation of continuous wires with uniform cross-section. The

heated plastic is pushed into the dye with the help of screw conveyor. In the dye, the plastic gets

cooled due to the exposure to atmosphere and by artificial air jets.

Extrusion moulding is used mainly for continuous moulding of thermoplastic materials into

articles of uniform cross-section like tubes, rods, strips, insulated electric cable. The thermo

plastic ingredients are heated to plastic condition and then pushed by means of screw conveyor

into a die, having the required outer shape of the article to the manufactured. Here the plastic

mass gets cooled, due to the atmospheric exposure. Along conveyor carries away continuously

the cooled product.

BOWLING MOULDING:

Blow moulding produces hollow plastic materials like bottles, tubes, tanks and drums. Thermo

plastic materials PVC, Polystyrene, Poly propylene can be blow moulded.

In this process, a tube is placed inside a two piece hollow mould. One end of the tube is

completely closed and heated and simultaneously air is blown to fabricate the product having

the shape of the mould.This similar to glass industry.

8


CASTING:

The moulding is usually made of lead. The molten resin are poured in the mould and cured at

about 70 degree Celsius for several days. The mould is removed re melted and a new mould is

again mould. This method is used for making special shapes. The products are water white in

color. The cost of production is high.

POLY-ETHYLENE:

Polymerization of ethylene gives poly-ethylene.

The ethylene gases liquefied using high pressure and then pumped into a heated vessel

maintained at 150-250 degree Celsius. By the catalytic effect on the oxygen present ethylene is

polymerized into poly-ethylene, a waxy solid which can be separated at the bottom of the vessel.

Poly-ethylene is of two types

(i) Low density polyethylene (LDPE)

(II) High density poly-ethylene (HDPE)

LOW DENSITY POLY-ETHYLENE:

Low density poly-ethylene (LDPE) is polymerized at high pressure of 5000 atmospheres and at

a temperature of 250 degree Celsius in the presence of oxygen as free radical inhibitor.

9


The presence of branches in the poly-ethylene molecules does not allow it to pack close

together, and hence, it`s density is low (0.912-0.94 gm/cc) and is known as low density poly

ethylene.

LDPE is chemically inert and a poor electrical conductor. It is used in films for packing, toys,

insulation wires, pipes etc.

HIGH DENSITY POLY-ETHYLENE:

It is polymerized under 6-7 atmospheric pressure at 60-70 degree Celsius in the presence of

zieglar-natta catalyst (TiCl4/AlR3) dispersed in an inert solvent.

The poly ethylene molecules produce by these methods are linear. The linear molecules can

pack themselves, the density of these poly ethylene molecules is high (0.95-0.97 gm/cm3)

HDPE is chemically inert but it is stiffer and harder than LDPE. They are used in toys, pipes,

bottles and in bags for packing. Because of the excellent insulation properties, it is used for wire

and cable coatings as well.

PROPERTIES:

Poly ethylene is a rigid waxy white translucent, non polar material exhibiting

considerable chemical resistance to strong acids, alkalis and salt solutions at room

temperature.

Good insulator of electricity.

Because of high symmetrical chain structure poly ethylene crystallizes very easily.

Poly ethylene produced at high pressure process has a branched structure and therefore

flexible and tough.

Low pressure process results in a completely linear poly ethylene.

High density poly ethylene which is completely linear has better chemical resistance to

organic solvents.

Low density poly ethylene has a low impact strength and is relatively brittle.

USES:

To prepare high frequency insulator parts, bottle caps, flexible bottles, kitchens and

domestic application toys.

Sheets for packing materials, chemical plants, tubes, pipes, coated wires and cables, bags for packing etc.

10


PVC (POLY VINYL CHLORIDE): By treating Acetylene at 1 (or) 1.5 atmospheric pressure with hydrogen chloride at 60-80

degree Celsius in the presence of metal chloride as catalyst.

Poly Vinyl Chloride is obtained by heating a water emulsion of vinyl chloride in the presence of

small amounts of Benzyl Peroxide (or) H2O2 under pressure.

PROPERTIES:

It occurs colorless, odorless, non-inflammable rigid material.

It is soluble in hot chlorinated hydro carbon such as ethyl chloride.

It is resistant to light, atmospheric oxygen, inorganic acids and alkalis.

It is having high density and low softening point.

It is most widely used as synthetic plastic.

USES:

It is mainly used as cable insulation, leather cloth, packing and toys.

It is used for manufacturing of film, sheet and floor covering.

PVC pipes are used for carrying corrosive chemicals in petro chemical factories.

POLY STYRENE(PS):

Poly styrene is also known as Poly Vinyl Benzene, which is a liquid with a pleasant odor, boiling point 45 degree Celsius.

Poly styrene is prepared by the Friedel crafts reaction between Benzene and ethylene.

It is further purified by distillation.

PROPERTIES:

It is transparent, light and good light stable, excellent moisture resistant.

Poly styrene is nitrated by fuming nitric acid and sulfonated by con H2SO4.

Above 100 degree Celsius it yields water soluble emulsion.

Highly electric insulating, resistant to acid and good chemical resistant.

11


USES:

Poly styrene is widely used in manufacture of articles like lids, jars, bottles, radio, television

cabinets, toys, foamed plastics, household goods etc.,

TEFLON (POLY TETRA FLUORO ETHYLENE):

Teflon is prepared by Polymerization of water emulsion of Tetra Fluoro Ethylene under

pressure in the presence of Benzoyl Peroxide as catalyst.

PROPERTIES:

It is a high crystalline polymer with a melting with a melting point of around 330 degree

Celsius.

It is extremely tough and exceptionally high chemical resistance towards all chemicals.

[This is because of high electro negative fluorine atom results strong attractive forces

between the chains]

They have very low dielectric constant and extremely good electrical and mechanical

properties.

USES:

It is used in making articles such as pump valves, pipes, tank linking, tubing, chemical

carrying pipes where chemical resistance is required.

It is used in non-lubricated bearings and its fiber is used to form belts, filter cloth,

impregnating glass fibers, coatings etc.,

BAKELITE:

The condensation product of phenol and formaldehyde gives active mono tri-methyl alcohol

monomer which in turn involves in poly condensation to give various linear (or) cross linked

polymer structures.

On further condensation with phenol

12


The properties of the products depend upon the factors like concentration of reactants, the

catalyst and temperature of reaction.

PROPERTIES:

They have outstanding electrical and mechanical properties and resistant to heat, water

and many chemicals.

It can be decomposed by strong caustic alkali and conH2SO4 and con HNO3.

They are hard and infusible and retain their shapes.

APPLICATIONS:

i. It is used in domestic plugs and switches.

ii. Handles for cookers and sauce pans.

iii. Adhesives for grinding wheels and brake linings.

iv. Varnishes, electrical insulation and protective coatings.

v. Production of ion exchange resin.

NYLON:

The condensation of di amines and dibasic acid gives a linear product.

Properties can be varied by varying the nature of acid and amine.

PROPERTIES:

The structure of Nylon is linear; it permits side by side alignment. The molecular chains

are held together by hydrogen bond.

They have high crystalline which imparts high strength, high melting point, elasticity

and toughness.

They are also sterilisable.

Nylon are poly polymers, they have good hydro carbon resistance.

APPLICATIONS:

Nylon-6,6 is primarily used as fibers, used in making socks, under garments, carpets etc.,

Nylon-6,6 is used in mechanical engineering for applications like gears, bearings, bushes,

cams etc.,

13


Nylon-6,6 moving parts can be operated without lubricants. They are silent running.

Nylon-11 and Nylon-12 are used for making flexible tubing for conveying petrol.

Moulding has applications in medicine and pharmacy because of sterilisability.

Nylon-6,6 is used for jacketing electrical material and to provide a tough, abrasion

resistant outer cover to protect primary electrical insulation

Durable hair combs.

Glass reinforced Nylon plastics are used in housing and casing of domestic

appliances,radiators parts of car.

On the basis of the raw material used the thermo plastic can be divided into two types:

1. Cellulose resin

2. Non cellulose resin

CELLULOSE RESIN: The important cellulose derivatives are its Nitrate, Acetates, Acetyl-butyrate, and

Propionate and methyl cellulose. Strong alkalis decompose most of the plastic material of

cellulose.

Weak acid and weak alkalis affect them slightly.

Cellulose plastic are very good electrical insulators.

Cellulose plastics having considerable strength and toughness.

The cellulose molecules have a longer chain (C6 H10 O5 )n.

This cellulose has three hydroxyl groups which can be esterified.

Cellulose Acetate: The normal cellulose on reacting with acetic anhydride (or) glacial acetic acid in the

presence of acid catalyst(H2 S O4) forms tri acetate ester which is partially hyrolysed and

forms cellulose diacetate.

(C6H7O2(OH)3)n + CH3COOH Con. H2 SO4 (C6H7O2(OCOCH3)3)n + 3nH2O

Cellulose Tri Acetate

(C6H7O2(OCOCH3)3)n + 2nH2O Hydrolysis (C6H7O2(OH)(OCOCH3)2)n +2n CH3COOH

Cellulose Di Acetate

PROPERTIES:

Cellulose acetates are:

1. They are tough.

2. Have high tensile strength.

3. They posses high dielectric strength.

4. They have some resistance to the mineral acids.

5. Cellulose acetates can be used in the form of plastics.

14


USES:

For the manufacture of Radio appliances , automobiles steering wheels, handles, windows,

goggles, combs, musical instruments etc.,

CELLULOSE NITRATE:

Cellulose on reacting with nitric acid in the presence of sulphuric acid, which acts as

dehydrating agent.

(C6H7O2(OH)3)n + 3nHNO3 Con. H2 SO4 (C6H7O2(NO3)3)n + 3nH2O

Cellulose Tri Nitrate

(C6H7O2(OH)3)n + 2nHNO3 Con. H2 SO4 (C6H7O2(OH) (NO3)2)n + 2nH2O

Cellulose Di Nitrate PROPERTIES:

1. Cellulose nitrate has many excellent properties like transparency, easiness for

fabrication and toughness.

2. Highly resistance to water, it is highly inflammable.

3. On exposure to air, the colored varieties gets discolored and then become brittle.

4. It is affected by strong acid and alkalis.

USES:

In toilet articles, pens, tooth-brushes, radio-dials, motion picture films, drawing

instruments, table tennis balls etc., It is soluble in many solvents and hence widely used for

making lacquers.

NON-CELLULOSE RESINS:

Plastics of this type are generally tough, chemically inert, non-

inflammable and have good electrical and water resistance properties.

Poly Acrylates comes under non-cellulose resin.

Poly Acrylates:

A large quantity of non cellulose plastics are derived from ethylene.

Acrylic esters are prepared from ethylene by converting it first to ethylene chlorohydrins,

then ethylene cyanohydrins which on esterification gives the Acrylates.

CH2 = CH2 + Hcl CH3 − CH2-Cl HCN CH3 − CH2-CN

Ethylene Chloro hydrin Ethylene Cyano hydrin

CH3 − CH2-CN +CH3OH Con.H2SO4 CH3 − CH2-COOCH3 + NH3

Methyl Acrylate

15


The ester obtain in this format can be polymerized to give the plastics called poly Acrylates. PROPERTIES: They are tough, strong, and have low specific gravity. USES: 1. Air craft’s and cockpit enclosures.

2. The thermoset resin is the phenolic resin.

3. The phenolic resin is similar to Bakelite.

CONDUCTING POLYMERS A Polymer which can be conduct electricity is termed as conducting polymers.

They are classified into two types:

INTRINSICALLY CONDUCTING POLYMER:

The polymer whish have extensive conjugation in the backbone for

conduction are called intrinsically conducting polymer.

These are further two types:

A). CONDUCTING POLYMER HAVING CONJUGATED π-electrons IN THE BACK BONE:

These polymers contain conjugated π-electrons in the back bone. The π-electrons increase the

conductivity. This is because overlapping of conjugated π-electrons results in formation of

valance bond as well as conduction bonds, which extends over the entire polymer molecule.

These two bands are separated by a signification gap.

Thus, electrical conduction could occur only after thermal (or) photolytic activation of

electrons , to give them sufficient energy to jump the gap and reach into the lower level of the

conduction band.

E.g.:- Poly Acetylene, Poly Quinoline etc.,

CONDUCTING POLYMERS

INTRINSICALLY CONDUCTING

POIYMERS

CONDUCTING POLYMERS HAVING CONJUGATED PIE-ELECTRONS IN THE

BACK BONE

DOPING CONDUCTING POLYMERS

EXTRINSICALLY CONDUCTING

POLYMERS

CONDUCTIVE ELEMENT FILLED POLYMERS

BLENDED CONDUCTING

POLYMERS

16


B). DOPED CONDUCTING PLOYMERS: Intrinsically conducting polymers posses low conductivity, but these posses low ionization

potential and high electron affinity, So these can be easily Oxidized (or) Reduced.

The conductivity of these polymers increased by creating either positive (or) negative charge on the polymers by oxidation (or) reduction.

This technique was called DOPING.

Doping was of two types:

1. P-Doping

2. N-Doping

P-DOPING:

This doping involves treating an intrinsically conducting polymer with a lewis acid , there by

oxidation process takes place and positive charges on the polymer back bone are created.

E.g.:- the p-do pants used are I2, Br2, Cl2, FeCl3, AlCl3

(C2H2)n + 2FeCl3 (C2H2)n+ FeCl4

− + FeCl2

Poly Acetylene

P-Doping also called as “oxidative doping”. N-DOPING:

This doping involves treating an intrinsically conducting polymer with a Lewis base there by

reduction process takes place and negative charges as the polymer back bone are created.

E.g.:- for n-do pant used are Li, Na, Ca tetra butyl Ammonium etc.,

(C2H2)n + B (C2H2)n− 𝐵+

Poly Acetylene Base n-doped Acetylene N-DOPING is also called “Reductive doping”. EXTRINSICALLY CONDUCTING POLYMER:

The polymer whose conductivity is due to the presence of “externally” added are called

extrinsically conducting polymers.

These are of two types: A).CONDUCTIVE ELEMENT FILLED POLYMER:-

It is a resin (or) polymer filled with conducting elements such as carbon-black, metallic fibers ,

metal oxides etc., In this , the polymer acts as the binder to hold the conducting elements

together in the solid entity. This polymer posses reasonably good conductivity. These are low in

cost , light in weight, mechanically durable and strong, easily process able in different forms ,

shapes and sizes.

Generally conducting carbon black is used as filler to its very high surface

area, high porosity and filamentous property.

17


B).BLENDED CONDUCTING POLYMERS:

It is obtained by blending a conventional polymer with a conducting polymer either by

physical (or) chemical change. Such polymers can be easily processed and posses better

physical, chemical and mechanical properties.

APPLICATIONS OF CONDUCTIVE POLYMERS:

Conducting polymers are found to be in increased use because they are light weight, easy

to process and have good mechanical properties. Some of the important applications of

conducting polymers are:

In Rechargeable Batteries: These batteries are small in size based on percholate doped

ploy acetylene –lithium system. These are about 10-times lighter than conventional lead

storage batteries.

In Optically display device used on polythiophene: Electro chromic system produce

coloured displays with faster switching time and better viewing than conventional liquid

crystals display device (LED).

In wiring in aircrafts and aero space components.

In tele communication systems.

In anti static coating for clothing.

In electromagnetic screening materials.

In electronic device such as transistors and diodes.

In solar cells, drug delivery systems for human body etc.,

In photo voltaic devices. e.g.; - Al/polymer Au photo voltaic cells.

In non-linear optical materials.

In molecular wires and molecular switches.

In Ion-exchange members: The charge residing on the conducting polymers make them

useful as ion-exchange membrane.

POLY ACETYLENE: Polymerization of Acetylene over Ziegler Natta catalyst gives poly acetylene which is mostly

formed in Cis form.

On rising the temperature of this film gives more stable Trans form.

This polymer is infusible, insoluble and tends to become brittle on exposure to air.

Conductivity is modified by doping.

18


Controlled addition of p-doping agent like Agf5, Br2I2,(or) HclO4 could still enhance the

conductivity.

POLY ANILINE: Reaction of Aniline with Ammonium per sulphate in aqueous Hcl produces poly aniline as a dark blue powder with a conductivity of 55 S 𝑐𝑚−1 DOPING: Doping in semi conductors is achieved by replacing an atom by electron rich (or) electron poor

atom to create p-type and n-type semi conductors. In conducting polymers, doping is achieved

through an oxidation (or) reduction process.

The doping methods are classified into two types:

1. Chemical doping

2. Electro chemical doping

CHEMICAL DOPING:

It involves, a polymer is exposed to an oxidant (Typically Bromine or Iodine) {or} reductant

(far less common, typically involves alkali metals).

E.g.:- Poly phenylene, phenylene sulphide.

ELECTRO CHEMICAL DOPING:

It involves a polymer coated working electrode suspended in an electrolyte solution, in which

the polymer is insoluble along with separated counter and reference electrodes. Electric

potential differences created a charge from the electrolyte to enter the polymer in form of

electron addition (or) removal.

E.g.:- Poly Acetylene, Ploy Pyrrole, Poly thio phene.

RUBBERS

These are high polymers which have elastic properties in excess of 300 percentage.

Characteristics:

1. They have a remarkable resistance to electricity.

2. They are elastic in nature.

3. They have a property of abrasive resistance and chemical resistance.

4. They have chemical resistance to petrol, mineral oils and some solvents.

5. They are used as excellent adhesives.

USES:

1. They are used as an insulating coating on wires and cables because of the remarkable

resistance to electricity.

2. The rubbers is used in making rubber bands, mechanical rubber goods, golf balls, tubes

for automobiles, aero planes and bicycles because of the nature of elasticity.

3. They are used for making rubber lined metal tanks and vessels used in chemical

industry, where corrosive chemicals ar to be processed.

19


4. Rubber hoses are used for water transmission for gardening, fire fighting etc.,

5. Sponge rubber is used for shock absorption, thermal insulation and sound insulation

process.

6. Foam rubber is used for making bed pillows, mattresses, cushions, auto motive pads and

under coating pad dings etc.,

7. Rubber gaskets are used for sealing various types of equipments.

8. Poly sulphide rubber is used as a “solid propellant fuel” for rocket motors.

NATURAL RUBBER: Natural rubber is a high molecular weight hydro carbon polymer represented

by a formulae (C5H8) X. It is obtained from a milky emulsion called Latex, which is a dispersion

of Isoprene.

Latex is obtained by tapping the bank of the tree Hevea Brasiliensis. These Isoprene

molecules polymerize to form long-coiled chains of Cis-poly Isoprene.

CH2CH2

CH3 ISOPRENE Natural rubber is made from a wide range of plants have brasillians and Gayule found in

Tropical and semitropical countries.

The Latex is taken into Buckets and transferred to a factory for treatment.

VULCANIZATION: To improve the properties of rubber, some chemicals like sulphur, hydrogen

sulphide, Benzoyl chloride etc., are added. Addition of sulphur is important. Heat the raw rubber

with sulphur to 100-400 degree. The added sulphur combines chemically at the double-bond of

different rubber springs.

Vulcanization serves to stiffen the material by a sort of Anchoring and preventing the Intra

molecular movement of rubber springs.

The extent of stiffness of vulcanized rubber depends on the amount of sulphur added.

20


ELASTOMERS (OR) SYNTHETIC RUBBER:

An elastomer (or) synthetic rubber is a vulcanizable man made rubber like polymer which can

be stretched at least twice its length but returns to its original shape and dimensions as soon as

stretching force is released.

Buna-S:- (GR-S)

Buna-S synthetic rubber is produced by co-polymerization of Butadiene and styrene.

nCH2 = CH – CH = CH2 + n CH2 = CH –Ph - (-H2C -CH = CH –CH --CH2 CH -Ph) n-

1, 3-butadiene (75%) Styrene (25%) PROPERTIES:

1. Styrene rubber resembles the natural rubber.

2. It posses high Abrasion resistance, high load bearing capacity.

3. It gets readily oxidized especially in the presence of traces of ozone present in

atmosphere.

4. It can be vulcanized similar that of material either by sulphur (or) sulphur mono

chloride.

USES:

1. Used in the manufacturing of motor tyres.

2. It is used for making foot wear components.

3. It is also used for insulation of wires and cables.

BUTYL RUBBER: (GR-I):

Co-polymerization of Isobutene with small amounts of Isoprene.

PROPERTIES:

1. Under normal conditions it is amorphous but it crystallizes on stretching.

2. It has excellent chemical resistance to heat, chemical and polar solvents.

3. It has good electrical insulating properties.

4. Due to low unsaturation, it can be vulcanized but it cannot be hardened much.

5. It is soluble in hydro carbon solvents like Benzene.

USES:

It is used for making cycle and automobile tubes.

21


It is used for insulating of high voltage wires and cables.

It is used for making conveyor belts for food and other material.

Thiokol rubber (or) poly sulphide Rubber (GR-P):

Thiokol Rubber is prepared by the condensation polymerization of sodium polysulphide(Na2s2) and

ethylene dichloride.

Properties;

They have excellent resistance to swelling and disintegration by organic solvents.

It has excellent resistance to oxygen, ozone and sunlight.

It undergoes swelling by Benzene and derivatives of benzene.

It has low tensile strength.

Uses:

It is used for the manufacturing of oil houses, chemically resistant tubing and engine

gaskets.

It is used for printing rolls

It is used for making containers for transporting solvents.

FIBERS

Fibers are those polymers whose chains are held by strong inter molecular forces like

“Hydrogen bonding”. They are crystalline in nature and of high tensile strength due to strong

inter molecular forces.

Biologically very important in both plants and animals .The ligaments that hold the tissue

material and basically fibers. Fibers are used for making textiles, utilities, rope, strings etc.,

Eg; Nylon, polyster etc.,

Based on their origin, fibers are classified into two types.

1. Natural fiber.

2. Synthetic fiber.

Natural fiber:

These are produced by plants, animals and geological materials.

They are environment friendly and bio-degradable.

These are of 4 types

I) Vegetable fiber.

II) Wood fiber

III) Animal fiber

IV) Mineral fiber.

22


Vegetable fiber:

They are basically cellulosic material and include cotton, jute etc.,

These fibers are used by us for making textiles,ropes,mats,paper,bags etc.,

Dietary fiber is an essential component of our food and its deficiency could result in

cancer.

Wood fiber:

The strength of the plant is due to the presence of wood fibers.Wood pulp is used in making

paper and wood fibers like jute are used for making bags.

Animal fiber:

They are largely made of proteins.

We move our limbs using the fiber present in them.

Spider silk is used for making special bullet proof jackets.

Mineral fiber:

Asbestos is a typical example of mineral fibers.

Mica and other minerals are also used as fibers.

Synthetic fiber:

These fibers are produced in large quantities and are cheaper than the natural

fibers.

Eg:poly amide,nylon,pvc,polyster,phenol,formaldehyde resins,poly ethylene are used in

making textiles.

Polyesters:

It is a synthetic fiber which have ester linkage in the main chain

It has 18% of synthetic polymer and 33.5% of poly ethane and 19.5% of poly propane.

Polyester is prepared by poly condensation of purified terphthalic acid(1,4 Benzene di

carboxylic acid)

(or)PTA and mono ethylene glycol (MEG)

+

Ter phthalic acid

23


Re in forced plastics

The combination of plastic material and solid fillers will hard plastic with good mechanical

strength and impart resistance known as reinforced plastics.

Fiber re-in forced plastics:

The fiber polymer with fillers to impart mechanical strength and hardness without losing

plasticity is known as FRP.

Ex:carborandum,quatz,mica,word,floor,paperpulp,cottonfibers,graphite,asbestors,glassfibers,ny

lonfibers,chinaclayetc.,

Composition:

About 50%of the mould able mixture contains fillers by weight; high amount may result

into a brittle material and break very easily.

Addition of carbon black to natural rubber gradually increases the tensile strength of

rubber up to 40% and such rubbers are used in the manufacture of tyres of various

vehicle.

Addition of china clay improves the insulation property of polymers like PVC, Teflon.

Calcium carbonate addition to PVC is used for insulator of tubing’s, seat covers, wires

and cables.

Asbestos filled FRP are largely employed for electrical appliances for insulation.

FRP possess very good shock and thermal resistance, mouldabilty, dimensionsal

stability and reparability.

Applications:

1) The base polymers like polythene,poly propane and nylon-6 are used for making door

Cases, exhausterfans, engine cooling fans etc.,

2) The polymers like nylon-6, polystyrene are used for making nose cones, pistol grips and

riffle bullets in Defence industry.

3) The polymers like nylon, PP and styrene, acryl nitrile are used for making computer

tape, insulators, Wires, cable insulations, switches, gear parts, exhaust fans etc.,

4) Nylon-6 is used as a polymer for making shuttle and textiles in textile industry.

5) The blended plastics like polypylene(pp) and acrylic butadiene,stryrene are used for

making the Consumer goods like doors, windows, tables, chairs, almars, cameras etc.,

6) The base polymers PVC, polypropylene and nylon-6 are used for making miscellaneous

items like Meters, chemical pomphousings, tubing’s, seat covering etc.

24


LIQUID CRYSTALS

Liquid crystals (or) meso phases:

A state of matter that is intermediate between the solid crystalline and the ordinary liquid

phases is known as meso morphic state (Intermediate form) (or) liquid crystals.

Solid Transition point Turbid liquids

Melting point clear liquids

(Or) Liquid crystals

Classifications of liquid crystals

Liquid crystals are classified into 2 types they are

1. Thermo tropic liquid crystals

2. Lyotrophic liquid crystals

Thermo tropic liquid crystals:

The liquid crystal which are formed when the temperature is varied are called thermo tropic

liquid crystals

There are 3 types.

a) Nematic phase

b) Cholestric phase

c) Smetic phase

Nematic phase:

The molecules in the nematic structure maintain a parallel (or) nearly parallel

arrangement to each other along the long molecular areas.

They are mobile in three directions and can rotate about one axis .this structure is one

directional.

Cholestric phase:

The Cholestric liquid crystal phase is composed of nematic mesogenic molecules

containing a chiral Center. The orientation order which exists resembles that of the

nematic phase on a local scale.

Smetic phase:

The world Smetic is derived from the Greek world for soap molecule in this phase show

a degree of Translation order not present in the nematic phase.

In Smetic state, the molecules maintain the general orientation order of nematics,but

also tend to align themselves in layers or planes.

Lyotrophic liquid crystals:

The compound that exhibit liquid crystalline behavior when mixed with another

substance(solvent) and with change of concentration in solution in solution are called

Lyotrophic liquid crystals.

Characterizations of liquid crystals:

The following are the parameters characterize liquid crystals.

Positional orders: This order refers to the extent to which an average molecule(or) group of

molecules show translational symmetric.

25


Orientation order: This order represents a measure of tendency of the molecules to align along

the director on a long-range basis.

Bond-orientation order: It describes a line joining the centers of molecules without requiring

a regular spacing along that line.

Physical properties:

Melting point: Liquid crystal passes a definite melting point at which they become true liquid.

Polymorphism: Liquid crystals compounds exhibits polymorphism. Polymorphism means the

condition where more than one phase is observed in the liquid crystalline state.

Anisotropy: The tendency of the liquid crystal molecules to point along the director leads to a

condition known as anisotropy. The anisotropic nature of liquid crystals is responsible for the

unique optical properties.

Effect of magnetic field: Substances in mesomorphic state are turbid, but when a magnetic

field is applied, they become clear in the direction of lines of force. The orientation order is

affected by magnetic field i.e., all the molecules are bundled in the same direction along the lines

of force.

Viscosity: The viscosity of liquid crystal is small. But the viscosity of liquid is more.

Chemical nature of liquid crystals:

The factor that control the chemical nature are linearly elongated molecules with

molecula Interactions lead to rod shaped structure

Molecular interactions brought up by dipole-dipole, dipole-included dipole interactions,

hydrogen Bonding and dispersion forces are in sufficient to bring about total 3D lattice

symmetric of crystals but Enough to bind them together leading to meso phases

Presence of unsaturation: The double bonds enhance the polarizability of the molecule and

bring inter molecular attractions to a level that is suitable for meso phase formation.

Suitable for mesophase formation.

Simultaneously double bonds prevents the benzene rings form twisting

O

OH

OCH3

OOHO

CH3

Trans-p-n-alkoxky cinnamic acid Cis-p-n-alkoxky Cinnamic acid

26


If the unsaturation is removed, the meso character is destroyed, due to twisting of chains

leading to isotropy.

Absence of bulky groups:

Bulky atoms like ‘Br’ are the bulky groups present in the chain other than as end groups. They

destroy the mesomorphic capabilities.

O

OH

BrCH3

4-decylo-3-Bromo-Benzoic acid

H-Bonding:

H-bonding often destroys the mesomorphic characters

I) By lengthening of molecular chains.

II) Very strong bonds bringing crystalline.

III) By allowing cross linking of chains and preventing the formation of linear chains.

The mesomorphic character of carboxylic acid is destroyed by hydrogen bonding.

Applications of liquid crystals

Liquid crystal technology had a major effect in many areas of science and engineering

technology as well as device technology. These are used as displays in digital wrist-watches,

calculators, panel meters, an advanced VGA computer screen. These also have potential use as

television display.

Liquid crystal display devices:

LCD (liquid crystal display) is the most common application of liquid crystal technology .

LCD consists of an tiny segments(pixels)that can be manipulated to present information

and it consists Primarily two glass plates with some liquid crystal material between

them. In general LCD’S use much less power than their cathode-ray tube counter parts.

27


The role of liquid crystal in the digestion and assimilitation:

When fats are mixed with bile, form a special type of liquid crystal known as emulsion. The

function of the sodium dodecyl sulphate (SDS) stimulates the addition of bile to the digestive

tract. Thus functioning of bile is facilitated by addition of sodium dodecyl sulphate (SDS).

Liquid crystal as lubricants:

Slippery substances are called as lubricants. They reduce the amount of friction between 2

surfaces that nove against each other liquid crystals have viscosity than corresponding liquids.

Currently liquid crystal are used in automobile engines of heavy machinery.

Liquid crystal thermometers:

The temperature dependent variation in the colour of choleteric liquid crystal is used in the

measurement of temperature and temperature gradients. Liquid crystal temperature sensors

can also be used to find out bad connections on a circuit board.

Other applications:

Liquid crystal can also be used for nondestructive mechanical testing of materials under

stress. This technique is also used for the visualization of radio frequency waves in wave guides.

low molar mass liquid crystal are used in erasable optical discs, full colour “electronic slides” for

computer aided drawing(CAD) and light modulators for colour electronic imaging

MULTIPLE CHOICE QUESTIONS 1. Natural rubber is

a)Isoprene b) nitrocellulose c) polyethylene d) Bakelite

2. The repeating unit of PVC is

a)Ethylene b)Tetra Chloro ethylene c) Acrylonitrile d)Vinyl chloride

3. Which of the following contains Isoprene units

a)Natural rubber b)Nylon-6,6 c)Dacron d)polyethylene

4. Nylon is a

a)vinyl polymer b)Poly amide c)polyester d)chloroprene

5. Bakelite is made by the action of

a)phenol and HCHO b)melamine and HCHO c)urea and HCHO d)ethylene and HCHO

6. Which of the following is a natural rubber

a)polyster b)glyptal c)starch d)nylon-6

7. Which of the following is a synthetic polymer

a)cellulose b)PVC c)proteins d)nucleosides

28


8. Heating of rubber with sulpher is known as

a)Galvanisation b)bessimerisation c)valcanisation d)sulphonation

9. Buna-S is a polymer of

a)butadiene b)butadiene and styrene c)styrene d)chloroprene and butadiene

10. Terylene is a

a)polyamide b)polyethylene c)poly vinyl chloride d)polyester

11. Which one of the following is thermosetting plastic

a)PVC b)PAV c)Bakelite d)Perspex

12. Polymer used in bullet proof glass is

a)PMMA b)Lexan c)nomex d)Kevlar

13. F2c = CF2 is a monomer of

a)Teflon b)glyptol c)nylon-6 d)buna-s

14. Soft drinks and baby feeding bottles are generally made up of

a)polyester b)polyurethane c)polyamide d)polystyrene

15. Which one is used to make non-stick cookware

a)PVC b)polystyrene c)poly ethylene tetra phthalate d)poly tetra flourethylene

16. Which of the following is not an example of addition polymer

a)polystyrene b)PVC c)polypropylene d)nylon

17. Cellulose acetate is a

a) thermoplastic b) thermosetting c) both d) None

18. An example of branched polymer is

a) polyester b) PVC c) Nylon d) Low density polymer

19.Additional polymerization is a kind of polymerization which produce

a) Exact multiple of the monomer unit b) different kinds of monomer units combined

product c) a product with the elimination of smaller molecules d) none of the above

20. A co polymer is made up of

a) same monomer units b) Different monomer units

c) both the above possible d) none of the above

21. In condensation polymerization

a) Addition of same kind of monomers takes place

b) Addition of different kinds of monomers takes place

c) polar group combine with the elimination of smaller molecules

d) none of the above

22. A good example of co-polymer is

a) Buna-S rubber b) PVC c) polythene d) polystyrene

29


23. A good example of condensation polymer is

a) Nylon6,6 b) PVC c) polythene d) polybutadiene co-styrene

24.Homo polymer is made up of

a) different kinds of monomer units b) same monomer units c) both are possible d) none

25. A good example of homo polymer is

a) PVC b) polystyrene c) polythene D) all of the above

26. Teflon is chemically

a) poly tetra flouro ethylene b) poly butylenes c)poly carbonate d)none

27. The following is a hetero polymer

a) PVC b) polystyrene c) silicone d) PMMA

28. Silicon polymer is made up on

a)carbon back bone b) sulpher and oxygen bone structure

c) silicon and oxygen back bone structure d) silicon back bone structure

29. High polymers are

a)liquids b) gases c) solids d) colloids

30. The polymerization in which two or more chemically different monomers take part is called

a)co-polymerization b) chain polymerization

c) additional polymerization d) homo polymerization

31. The structural units of polymers are called

a) fibers b) monomers c) fabrics d) thermo units

32. A thermo plastic resin is formed by the phenomenon of

a) rubber b) nylon c) PVC d) Bakelite

33. Polymer commonly use in textile industry is

a)Rubber b)nylon c)PVC d)Bakelite

34. The following is a high molecular weight material that can be moulded to any desired

shape

a)Graphite b) jelly c) resin d) greese

35. A plastic resin which becomes soft on heating and rigid on cooling is called

a) Thermo elastic b) Thermo plastic c) thermite d) thermosetting

36. Which of the following is an elastomer

a) PVC b) nylon c) poly styrene d) butyl rubber

37. The most commonly used reagent for vulcanization of natural rubber is a)graphite b)sulpher c)carbon black d) dry ice

38. Ebonite is

a)natural rubber b)synthetic rubber

c)vulcanized with >30%sulpher d)vulcanized with 3-5% sulpher

30


39. One of the important uses of Bakelite is for making

a)cables b) cloth c) electrical switches d) conveyor belts

40.Which one of the following is not a macro molecule

a)cables b)rubber c)protein d)wood

41.The following polymer has ester links in its structure

a)Nylon b)Bakelite c)PVC d) terylene

42. The common catalysts used in co-aodination chain polymerization

a)Nickel b) zeigler-natta catalyst c) zeolyte d) platinum

43. Functionality of phenol is

a)1 b)2 c)3 d)6

44. The only rubber which cannot be vulcanized is

a)butyle rubber b)Thiokol rubber c)neoprene d)nitryle

45. Styrene rubber is produced by co-polymerization of

a) butadiene and styrene b)butadiene and acrylo nitryle c) styrene and isoprene

d) butadiene and vinyle chloride

46. Butylrubber is produced by co-polymerization of

a)Isobutene & chloroprene b)Isobutene & Isoprene c)Isoprene & chloroprene d)Isoprene

47. Polyurethane rubber is also known as

a)hypanol b)Thiokal c) neoprene d)Isocyanate

48. The common reinforcing reagent to give strength and rigidity to rubber is a)carbon black b)mercaptol c)phenyl naphthyl amine d)wax

49.The common plasticizers used for compounding of plastic resins is

a)ZnO b) acetyle sulphuric acid c) vegetable oils d)benzoil peroxide

50. Plasticizers are materials which are added to resins to increase their ___________

a)strength b)corrosion resistance c)stability d)plasticity and flexibility

51. Compression moulding is used for moulding of

a)Thermo plastic & thermosetting resins b)only thermoplastic resins

c)only thermosetting resins d)neither thermoplastic nor thermo settingresins

52. Thermosetting resins fabricated by the transfer moulding which uses the principle of

a)blowing b) extrusion moulding c) injection moulding d)compression moulding

53. The least functionslyty of a monomer is convert to polymer is

a)1 b) 3 c) 2 d)6

54. If the arrangement of the functional groups on carbon chain is alternating its called

a)Isotactic b) syndiotactic c)atactic d)tacticity

31


55. Which of the following is co-polymer

a)SBR b) buna-S c)both a&b d) none

56. Coagulation of natural rubber is carried by adding

a)CH3COOH b)HCL c)alum d)detergent

57. Which one of the following is a co polymer

a)nylon 6,6 b)Teflon c)PVC d) poly butadiene

58. Polyester belong to the __________type of polymer

a)Addition ,thermoplastic b)addition ,thermosetting c)condensation ,thermoplastic

d)condensation ,thermosetting

59. Natural rubber is a ____________polymer of _______monomer

a)Addition , chloroprene b) condensation , chloroprene

c)addition , Isoprene d)condensation ,Isoprene

60. Polymer obtained by the condensation polymerization is

a)PVC b) Teflon c) nitrite rubber d) Bakelite

FILL IN THE BLANKS

1. Injection moulding for fabrication of thermo plastic resins. 2. Latex is the dispersion of Isoprene molecules.

3. LDPE has low or less melt nor specific gravity than HDPE.

4. An example of the thermosetting homo polymer is nylon 6.

5. Stereo specific polymers are obtained by co-ordination chain polymerization.

6. The plastic used for making optical lenses is PMMA.

7. A polymerization in which two or more different monomers take part is called

co-polymerization.

8. The trade name of poly methyl methacrylate (PMMA) is Plexiglas.

9. Nylon 6 is a polyamide.

10. The repeating unit of natural rubber is Isoprene.

11. Silicones contain alternate silicon oxygen structure.

12. Mono methyl silicon chloride gives cross linking o the final polymer .

13. Liquid silicons possess wetting power .

14. Silicon rubber is vulcanized by peroxides.

15. The polymer produced by treating di iso cyanate and diol is polyurethane

16. Kevlar is less flexible than nylon because of tight packing chains.

17. The polymerization in which same type of monomers take part is

called homopolymerisation.

18. The raw materials used for the manufacture of poly ester are glycol and terpthalic acid.

19. Buna-S is a copolymer of butadiene and styrene .

32


20. Caprolactum is a monomer of nylon-6.

21. Transfer moulding is a method used for fabrication of thermosetting resins.

22. Electric cables are fabricated by compressing moulding .

23. Compression moulding is a fabricating method applied to both thermoplastic

and thermosetting resin.

24. Lead salt or any white lead or lead chromate/litharge red lead /lead silicate

/lead naphthalene is an example of stabilizer added to poly vinyl chloride

during fabrication.

25. Resin holds the different constituents of plastics.

26. A flaw less glossy finish to plastics is given by lubricants.

27. The combination of compression and extrusion moulding is adopted in

thermo forming technique.

28. Polyacetylene / polyanilene is conducting polymer.

29. Tarpaulin is an example of fiber reinforeced plastic.

30. The liquid crystallinity in polymer may occure by solving or heating.

31. Styrene rubber is used for making tyres.

32. The only elastomers which does not require vulcanization is called Thiokol.

33. Blowing is used for the fabrication of bottles.

34. Silicones are the elemento-organic polymers.

35. In SBR-rubber the percentage of styrene is 24% and the percentage of 1,3-butadiene

is 75%.

36. Peroxides can be used as free radical indicator.

37. In buna-N rubber the percentage of acrylonitrile is 25% and the percentage

of butadiene is 75%

38. Teflon polymer is having excellent insulating properties.

39. Natural rubber is used for making tyre tubes.

40. Bakelite is used for making electric switches.

41. Thiokol rubber can be used for making gaskets.

42. Butyl rubber is co-polymer of Isobutene and small amount of butadiene.

43. Bakelite is used for making electric switches.

44. Phenolic resins are permanent setting resins.

45. Thermoplastic resins are formed by additional polymerization .

46. Thiokol rubber is made by the reaction between ethylene di chloride and

sodium tetra sulphide.

47. Vulcanization of rubber improves its properties like strength and brittleness.

48. Nylon-6 used for making tirecords and major application is in the textile industry.

49. Nylon-6,6 is obtained by polymerization of hexamethylene di amine and adipic acid.

33


IMPORTANT QUESTIONS

1. Describe “Addition” and “Condensation” polymerizations with suitable examples, explain the

difference between them. (Dec 210, June 2010)

2. Discuss the preparation, properties and applications of the following polymers.

(Dec 2010, June 2010, June 2011)

a) Nylon (6, 6) b) Bakelite c) polythene. d) PVC

3. Explain the differences between thermo plastics and thermoset plastics.

4. Write short notes on (June 2010)

a) phenol-formaldehyde resin b) Thiokol c) Teflon

5. Write notes on a) Fabrication of plastics b) compounding of plastic.

6. What are elastomers? Write the preparations of Buna-S, Butyl rubber and Thiokol rubber

(Dec 2010, June 2011)

7. Explain the preparation of Natural rubber? (Dec 2010, June 2011)

8. Write about composition of FRP and its applications.

9. Write a note on Conductive polymers.

10. Discuss the preparation properties and uses of various grades of polyethylene.

11. Describe the preparation, properties and uses of BUNA-S rubber, Butyl rubber &

Thiokol rubber.

***

Documents

Polymers Unit III