unit 4 polymer BT101_1674199439.pptx

Engineering chemistry
BT-101
Unit -4
Polymers and polymerization
Content-
 Definition.
 Degree of polymerization.
 Classification.
 Polymerizations.
 Reaction mechanism.
 Examples in details.

A word polymer is a combination of two Greek words
“poly” means “many” and “Meros” means “parts or units”.
n(CH2=CH2)
ethylene
(-CH2-CH2-)n
polyethylene
A polymer is a long molecule by the joining together of thousands of
small molecule or monomer units by chemical bonds. Due to their large
size they are also called macromolecules.

Degree of polymerization refer to the number
of repeating monomer units in the polymer
chain. For example-
here, n is degree of polymerization
n(CH2=CH2)
Ethylene
monomer
(-CH2-CH2-)n
Polyethylene
polymer

4
3 C H 2 = C H 2 C H 2 C H 2
3
Degree of Polymerization (n) = M/m;
Where, M= Mass of Polymer; m = mass of monomeric unit
Polymerisation
polyethylene
Ethylene
Degree of polymerization (n) = 3
Mass of this polymer M = (28 x 3) = 84Da

Functionality
O
HO C CH2 NH2
OH CH2 CH C OH
NH2
Ex. Serine
Linear chain polymer is formed if the functionality of the
monomer is only two (Bifunctional)
Ex. Glycine
The number of reactive sites (like-NH2,-OH,-COOH,-SH etc)present in a
monomer is called functionality
1.
2.
Cross linked chain polymer is formed if
the functionality of the monomer is
more than two (multifunctional)
O

Classification of Polymers
Classification based on source
1.Natural polymers
E.g., Proteins, Cellulose, Starch,Rubber
2. Semi-synthetic polymers
E.g., Cellulose derivatives - Cellulose
acetate (Rayon)
3. Synthetic polymers
E.g., Buna-S, Buna-R, Nylon, Polythene,
Polyester.

Classification based onStructure
1. Linear polymers
consist of long and straight chains. E.g., Polyvinyl chloride
2. Branched chain polymers
contain linear chains having some branches, e.g., low density polymer.
3. Cross-linked or Network polymers
formed from bi-functional and tri-functional monomers and contain
strong covalent bonds e.g. bakelite, melamine,

6
Classification - based on Tacticity or arrangement of polymer
Representation of polypropylene polymer – orientation of side groups
around the main backbone chain.
H H H
CH2 C CH2 C CH2 C
H
CH2 C CH2 C
CH3
H
CH3 CH3
CH3
CH3
H H H
CH2 C CH2 C CH2 C CH2 C CH2 C
H H
CH3
3
CH3 CH3
CH3
H H H
CH2 C CH2 C CH2 C CH2 C CH2 C
CH H H CH3
1. Isotactic polymers
Functional groups on the
CH3 same side of the main carbon
skeleton
CH3 CH3 CH3
Functional groups arranged
in the alternate fashion of the
main carbon skeleton
3.Atactic polymers
Functional groups arranged
in a random manner around
the main carbon skeleton
2.syndiotatic

A macromolecule may consist of monomer of identical or different
chemical structure and accordingly they are called Homopolymers or
copolymers (or Heteropolymers).
Classification based on types of monomer units
A A A A …
Homopolymers
A A B A …
Copolymers

C la ssifica tio n based on End Uses
1.Elastomers
e.g. Rubber, Buna-S, Buna-N, neoprene
2. Fibers
eg. Polyesters, Polyamides.
3. Plastics
e.g. PVC.
4. Adhesives
e.g. Epoxy resins

Classification based on conductance
almost all polymers are insulators but polyaniline and polypyrrole
conduct electricity.
Classification based on environmental friendly
Polymeric material are durable and some are biodegradables i.e strach
based polyethylene.

Classification based on their behaviour when heated
On this basis polymer are broadly divided into two catagories .
1. Thermoplastics e.g. (PE, PVC, Nylon etc).
2. Thermosets e.g. (Epoxy, Phenol - formaldehyde resin etc).
Thermoplastics (fig .1)
In thermoplastics, polymer chains are held together by weak forces
of attraction i.e. Vander Waal's forces or dipole-dipole forces or by
hydrogen bonding.
a) Weak bonds between polymer chains get easily broken on
heating
b) polymer is then moulded into new shapes by processing.
c) weak bonds reforms in a new shapes by cooling, so new shape
sets and ready for use.

Thermosets
Thermosets have extensive crosslinking formed by strong covalent
bonds. Bonds prevents the structure and on heating polymer chains
cannot be easily broken.
Old shape
new shape
a)Heating
b)Molding
c)Cooling
Fig1.
Heating
cross-linking formed by strong covalent
bonds
Polymer keeps shape on heating

Classification based on mode of Polymerisation
1. Addition polymers
formed by the repeated addition of monomer molecules
possessing double or triple bonds.
n(CH2=CH2)
Ethylene
-(CH2 -CH2 )-
polyethylene
2. Condensation polymers
formed by repeated condensation reaction between two
different bi-functional or tri-functional monomeric units.
eg. terylene (dacron), nylon 6, 6, nylon 6.
Adipic acid hexadiamine nylon 6,6
here, R and R’ represent carbon skeleton

It is the process by which simple (monomer) molecules
joined together to form very large (polymer) molecules.
Hence, the synthesis of large molecular weight polymer
is termed as polymerization.
Polymerization
Polymerization:-
monomers
Chemical
bond
monomer
Polymeric chain
repeating units

There are three different ways for doing polymerization
a). By Opening a double bond:-
n(CH2=CH2)
Ethylene
monomer
(-CH2-CH2-)n
Polyethylene polymer
b).By Opening a ring:-
c).By :- using molecules having two functional groups:-
Adipic acid hexadiamine nylon 6,6

Polymerization broadly classified into two
1. Addition polymerization
2. Condensation polymerization
1.Addition polymerization;-polymer synthesised by addition
polymerization has same emperical formula as that of monomer. No
molecule is evolved during polymerization and the polymer is an exact
multiple of the original monomeric molecules.

Condensation polymerization:-
It takes place by the condensation of two different bi- or poly-
functional groups which have affinity for each other. For example, -
COOH and –OH or –COOH and NH2 carrying monomers undergo
condensation polymerization.
 It always accompanies with the elimination of small molecules like
H2O and HCl etc.

Reaction Mechanism:-
In free-radical polymerization, monomer is activated by its transformation into
radical by that action of light (as in photochemically initiated), heat (as in
thermally initiated), or by adding chemicals, known as initiators, (as in chemically
initiated) free radical polymerization.
Initiators are the compounds which readily decompose into free radicals so that
monomer molecules can interact with these free-radicals for their activation.
Azobis iso butyronitrile
Such reactions can be written in general as: In 2R

Chain polymerization occur in three steps
Chain initiation
Chain propagation
Chain Termination

A free radical is first generated as a result of physical or chemical
effect, which is responsible for the further continuation of the
chain polymerization.
Homolytic cleavage is occurred.
Initiators

The primary free radical react with the double bond of an unexcited
monomer molecule and adds to it forming a new radical capable of
further interaction with the initial monomers.
Step – I Chain Initiation –
Step-II Chain Propagation-

The most common termination processes are Radical Combination
and Disproportionate.
These reactions are illustrated by the following equations.
Step – III Chain Termination

Copolymerisation:-
is a polymerization reaction in which a mixture of more than one monomeric species is
allowed to polymerize and form a copolymer. For example, a mixture of 1,3–butadiene
and styrene can form a Co-Polymer

 In condensation polymerization, the chain growth is by elimination
of small molecules.
 The molecules are in the form of the water molecule H2O ;
methanol molecule CH3OH ,etc.

It involves a repetitive condensation reaction between two bi- function monomer.
Example:- formation of Nylon 6,6
n HOOC(CH2)4COOH +nH2N(CH2)6NH2
[-N-(CH2)6-N-C(CH2)4-C-]n
H O
O
Nylon6,6
Step Growth polymerization

Cationic Polymerization
In cationic chain polymerization, the propagating species is a carbocation. Initiation is
brought about by addition of an electrophile to a monomer molecule as
the alkene monomer
reacts with an electrophile

The anionic polymerization is the same as other chain polymerizations which involve three
reaction steps: (1) initiation, (2) propagation, and (3) termination, using the base or
nucleophile as an initiator, e.g., NaNH2,alkoxides, hydroxides, cyanides, phosphines, amines,
and organometallics compounds such as n-C4H9Li and C6H5–Mg-Br. Alkyl lithium is the most
useful initiator and used to initiate 1,3-butadiene and isoprene commercially
Non terminated chains are called living polymers The chains remain
active until they are killed.
Anionic Polymerization:-

Examples of Daily Use Polymers

Examples of polymer in
details

There are mainly two types of polythene:
Low density polythene(density range of 0.910 – 0.940g/cm3):
 Itis obtained by the polymerization of ethene under high pressure of
1000-2000atm at a temperature of 350-570Kin the presence of traces of
oxygen or a peroxide catalyst.
 Efficient cooling is a must and is done via cooling towers.
 It is created by free radical polymerization.
Polyethylene(PE)/Polythene

Properties:-
1.High degree of short and long chain branching.
2.intermolecular forces is less.
3.Tough but highly flexible & ductile.
4.LDPE is Chemically inert and has excellent chemical
resistance.
Uses:-
LDEP is used in following applications.
1. Films for general packaging and carrier bags,
2. Squeeze bottles particularly for detergents,
3. Molded toys,
4. Ink tubes for pens and
5. Mugs .

Limitations of LDPE:-
a). Because of low density and %crystallinity, LDPE has low
rigidity and is not suitable for load bearing applications. For
instance if pipes are made from LDPE for domestic water, they will
undergoes creep.
b).LDPE is permeable to gas molecules because of pours or free
zone to facilitates the passage of small molecules. Hence, LDPE
is also not suitable for the manufacturing of pipes for distribution of
gas.

Properties:
1.HDPE molecules are linear and their packing is easy. Hence HDPE has high
density (0.95-0.97) and more percentage of crystallinity (80-90%).
2.Softening temperature of HDPE (135 degree celsius) is also higher than
LDPE.
3. HDPE has excellent chemical resistance.
4. It has excellent electrical insulation properties.
5.HDPE has low water and gas permeability.
6.It is free from odour and toxicity.
7.It is more stiff ,hard and greater tensil strength.
1. Manufacturing of HDPE by low pressure method density >= 0.941 g/cm3):
formed when addition polymerisation of ethene takes place in a hydrocarbon
solvent in the presence of a catalyst such as triethylaluminium and titanium
tetrachloride (Ziegler-Natta catalyst) at a temperature of 333-343 K and under a
pressure of 6-7 atm.
2. Polymerization by a supported metal oxide catalyst (5% CrO3).
3. Polyethylenes of highest density (0.941g/cm3) can be obtained by this process.

Uses:-
• for manufacturing buckets, dustbins, bottle water pipes.
• It can also be used for domestic water and gas pipings.
• Bottles for milks, household chemicals and drugs packaging are also
made from it.
Environmental issue
• Although polyethylene can be recycled, most of the commercial
polyethylene ends up in landfills, and in the oceans such as the
Great Pacific Garbage Patch.
• Polyethylene is not considered biodegradable, except when it is
exposed to UV from sunlight. Under UV lights tertiary carbon bonds
in the chain structures are the centres of attack.
• The UV rays activate such bonds to form free radicals, which then
react further with oxygen in the atmosphere, producing carbonyl
groups in the main chain.

• It is a vinyl polymer constructed of repeating vinyl groups
(ethnyls) having one of their hydrogens replaced with a chloride
group.
• Obtained by heating a water emulsion of vinylchloride in
presence of benzyl peroxide/ hydrogen peroxide in an
autoclave at temperature (45-47 Celsius) under high pressure.
Polyvinyl chloride
Vinyl chloride (monomer) polyvinyl chloride (polymer)

PVCs are Colourless , odourless.
PVC is Non-inflammable &chemically inert
 PVC has greater stiffness &rigidity than polyethylene but brittle.
 Presence of chlorine atoms on the alternate carbon atoms of PVC
with dipole causes an increase in inter chain attraction. This increase
the hardness and stiffness of polymer.
 It has superior chemical resistance but soluble in ethyl chloride and
tetra hydro-furan.
 It has high resistance to oil.

Uses:-
Third most widely produced plastic
 Unplasticized PVC: Highly rigid but brittle, for making sheets,
tank lining, helmets ,mudguards etc.
 Plasticized PVC(by adding plasticizers e.g. phthalates):
Making continuous sheets of varying thickness, hoses,
pipes, construction, table covers, conveyor belts etc.
 It is also used for making bottles.
for consumable liquids ( like edible oils, fruits squashes,
table wine and vinegar).

Polytetrafluoroethylene (TEFLON)
•It is obtained by polymerization of water-emulsion of
tetrafluoro ethylene, under pressure and in the presence
of benzoyl peroxide as a catalyst.

 Due to presence of high electronegative fluorine in structure of
TEFLON, strong interchain forces are present which make it extremely
tough.
 High softening point (350°c).
 Ithas high chemical resistance.
 It has good mechanical and electrical properties(high-performance
substitute for polyethylene).
Properties:-

 It is used in insulating motor, transformers.
 It is used in making wires.
 Non-stick cookware coatings are made from
teflon for eg. In frying pan.
 Also used for making gaskets, tank linings, pipes and tubes for
chemical industries.
 Used for making non lubricating bearings.
 one of the lowest coefficients of friction against any solid
Use
s

Polystyrene is actually an aromatic polymer, made from the monomer styrene. It is a
long hydrocarbon chain that has a phenyl group attached to every carbon atom.
Styrene is an aromatic monomer, commercially manufactured from petroleum.
Polystyrene is a vinyl polymer, manufactured from the styrene monomer by free
radical vinyl polymerization.
Polystyrene

 polystyrene is generally flexible and can come in liq form, moldable solids or viscous
liquids.
 The force of attraction in polystyrene is mainly due to short range van der Waals
attractions between chains.
Properties

 kitchen appliances, model cars and airplanes, toys, molded parts in car are
all made of polystyrene.
 It is use for packaging and insulating.
 Polystyrene is generally flexible and can comein the form of moldable solids
or viscous liquids.
Uses:-

Acrylonitrile Butadiene Styrene
•Monomers:-Acrylonitrile , Butadiene, Styrene
•Formula :-(C8H8·C4H6·C3H3N)n
•Production :-Copolymer made by polymerizing styrene and acrylonitrile in the presence of
polybutadiene. The proportions can vary from 15 to 35% acrylonitrile, 5 to 30% butadiene and
40to 60%styrene.
•Properties :-The styrene gives the plastic a shiny, impervious surface.
•The butadiene, a rubbery substance, provides resilience even at low temperatures.
•Mechanical properties vary with temperature.
•Application :-
1.Used to make light, rigid, molded products such as piping.
2.Musical Instruments.
3.Golf club heads :- Used due to its good shock absorbance
4.Used as a colorant in tattoo inks.

Is a transparent thermoplastic, often used as a light or shatter-resistant
alternative to glass.
Synthetic polymer of methyl methacrylate, Can be made by all types of
molding processes.
PMMA is also known as Plexiglass or Lucite.
It is prepared by the polymerization of methyl methacrylate in the
presence of acetyl peroxide or hydrogen peroxides as catalyst.

1.It is amorphous, colorless, transparent thermoplastics with high optical
transparency.
2. Methyl groups as substituents on the alpha carbon atoms restrict chain
flexibility that’s why PMMA is hard.
3.It is a polar polymer, hence does not have electrical insulation properties
compare to polyethylene.
4.It has high softening point (about 130-140 degree centigrade), due to dipole
–dipole interaction i.e weak forces.
5.Good impact strength ,higher than both glass & polystyrene.
6.Transmits up to 92% of light & filters UV lights.
7.coefficient of thermal expansion is relatively high.
8.Its properties can be modified to suit requirements.

Making aquarium glasses;
 automobile headlights;
 Aircraft windows;
 Helmet visors;
 making acrylic paints;
 bone cement,
 contact lenses etc.
Uses:

Polyvinyl Acetate(PVA)
• Catalyst used is either benzoyl peroxide or acetyl chloride. A solution of
vinyl acetate (monomer) and catalyst is prepared in benzene. This solution
is introduced into a jacketed vessel at 72 degree, for 5 hours (heating).
• It is a colorless, nontoxic thermoplastic resin prepared by the
polymerization of vinyl acetate. Polyvinyl acetate (PVAC) It is one of the
most widely used water-dispersed resins.
• Polyvinyl acetate water-based emulsions have been used as latex
house paints, artists' media (since 1945), and common household
white glues..
• It is commonly referred to as wood glue, white glue, carpenter's glue,
school glue.

PROPERTIES
 It is clear , colourless, and transparent material.
 It is amorphous polymer and has low temperature (28 degree)
Hence, the articles formed from it are distorted even at room temp,
under the influence of compressive and tensile forces.
 Lower molecular weight polymer weight polymer become gum like
when masticated and hence are used for making chewing gums,
since it is harmless, when taken orally.
 It is fairly soluble in organic solvents.

Uses
• PVAwater-based emulsions have been used as latex house paints.
• Making commonly used household white glues.
• Making wood glue.
• Makin paper glue.
• Adhesives.
• Glues for porous material.
• Used as a primer for drywall and other substrates.
• As a mortar additive.

7
(free radical Polymerization)

 Polyacrylonitrile(PAN) is the synethic semicrystalline resin.
 Thermoplastic in nature.And donot melt under the normal
conditions.
 Its resins flammable.
 Used for making textile fibers,military aircraft,tennis racket,tents,high
tech bicycle,pressure vessels and fishing rods,carpets etc.
POLYACRYLONITRILE

PHYSICAL PROPERTIES
Low permeability to gases
Hard and rigid
Slow to burn
Chemical and solvents resistant
Low density
Melting point
>300ºC if heating rate
50/min
Degradation temperature
Above 300ºC
Glass transition temp.
87ºC
COMMERICAL A
VAILABILITY Liquid(resins)

 Used for military purposes.
 Used in aircraft body
 Used in hi-tech bicycle.
 Used in rocket motors and components to provide
insulation case.
 Used in tents.
 Used aselectrolyte seperators in batteries.
 Acrylic fibers areused asfilters in industries.
 Used in fireproof clothes.
Applications:-

NYLON 6
Introduction
 Nylon 6 or polycaprolactam is a polymer developed by Paul to reproduce the
properties of nylon 6,6.
 Nylon 6 is a family of polymers called linear polyamides.
 Nylon-6 is made from a monomer called caprolactam.
 It is formed by ring-opening polymerization.
 It is a semi-crystalline polyamide.
 Nylon is produced by melt spinning.
 Available in monofilament, and multi-filament form.
 It is sold under numerous trade names including Perlon, Capron, Ultramid.
3

Caprolactam
 Caprolactam is an organic compound.
 This colourless solid is a lactam (a cyclic amide) of caproic acid.
 Caprolactam is the precursor to Nylon 6, a widely used synthetic polymer.
 Caprolactam was first described in the late 1800s when it was prepared by
the cyclization of aminocaproic acid, the product of the hydrolysis of
caprolactam.
 Caprolactam: Crude oil → benzene → cyclohexane → cyclohexanone
→ cyclohexanone oxime → caprolactam
6
2

Synthesis and production of Caprolactam
 Many methods have been developed for the production of caprolactam.
 Most of the caprolactam is synthesised from cyclohexanone, which is
first converted to its oxime.
 Treatment of this oxime with acid induces the Beckmann rearrangement
to give caprolactam:
 The other methods involves formation of the oxime from cyclohexane
using nitrosyl chloride. NOCl
 Cyclohexane is less expensive than cyclohexanone.
6
3

Polymerization Process
 Nylon 6 can be modified using co-monomers or stabilizers during
polymerization to introduce new chain end or functional groups.
 Nylon 6 is only made from one kind of monomer, a monomer called
caprolactam.
 It is synthesized by ring-opening polymerization of caprolactam .
Caprolactam has 6 carbons, hence 'Nylon 6'.
 Caprolactam is heated at about 533 °K in an inert atmosphere of nitrogen
for about 4-5 hours, the ring breaks and undergoes polymerization.
 Then the molten mass is passed through spinnerets to form fibersof nylon 6
6

Cont.
 During polymerization, the amide bond within each caprolactam molecule
is broken.
 With the active groups on each side re-forming two new bonds as the
monomer becomes part of the polymer backbone.
 All nylon 6 amide bonds lie in the same direction.
 Two ways to carry out a ring-opening polymerization of caprolactam.
Nylon 6 is made using a strong base as an initiator.
 Carried out in a semi batch reactor .
7

Properties of Nylon 6
 Nylon 6 fibres are tough, possessing high tensile strength, as well as
elasticity and lustre.
 They are wrinkle proof and highly resistant to abrasion and chemicals
such as acids and alkalis.
 The glass transition temperature of Nylon 6 is 47 °C.
 As a synthetic fiber, Nylon 6 is generally white but can be dyed to in a solution
bath prior to production for different color results.
 Its melting point is at 215 °C and can protect heat up to 150 °C on aver1a5ge.

Some Major Nylon Fiber Uses
 Apparel: Blouses, dresses, foundation garments, hosiery, lingerie,
underwear, raincoats, ski apparel, windbreakers, swimwear, and cycle wear
 Home Furnishings: Bedspreads, carpets, curtains, upholstery
 Industrial and Other Uses: Tire cord, hoses, conveyer and seat belts,
parachutes, racket strings, ropes and nets, sleeping bags, tarpaulins, tents,
thread, monofilament fishing line, dental floss

Nylon ropes and cords are high strength and have excellent UV and
abrasion resistance. They are resistant to mildew, motor fuels, oils,
cleaning fluids and many other chemicals. Do not float.
Nylon Rope

Nylon in Medical:
This is a synthetic polyamide material, which can be used in the form
of:
• Monofilament
• Multifilament
• Braided
The main disadvantage is that a triple knot must be tied.

Nylon conveyorbelt Rolex Nylon Strap
Nylon friendship
bracelets
30mm army nylon belt buckle

INTRODUCTION:-
 It is made of repeating units linked by amide bonds and is
frequently referred to as polyamide. Nylon was the first
commercially successful synthetic polymer.
 Nylon fibres are used in many applications, including fabrics, bridal
veils, carpets, musical strings, and rope. Solid nylon is used for
mechanical parts such as machine screws, gears and other low- to
medium-stress components previously cast in metal.
 Nylon 6,6 is a polyamide from nylon class. Nylons come in many
types, and the two most common for textile and plastics industries
are nylon 6 and nylon 6,6
 The polymer is made of hexamethylenediamine and adipic acid,
which give nylon 6-6 a total of 12 carbon atoms in each repeating
unit,.
NYLON 6,6

MANUFACTURE
Nylon 6,6 is made of hexamethylenediamine and adipic acid, which give
nylon 6,6 a total of 12 carbon atoms, and its name.
1. Hexamethylene diamine and adipic acid are combined with water in a reactor.
This produces nylon salt. The nylon salt is then sent to an evaporator where
excess water is removed.
2. The nylon salt goes into a reaction vessel where a continuous polymerization
process takes place. This chemical process makes molten nylon 6,6.
3. The molten nylon 6,6 undergoes a spinning process, where the nylon 6,6 is
extruded and sent through a spinnerett which is a small metal plate with fine
holes. The nylon is then air-cooled to form filaments.

n H (CH2)6 N
N
H
H
H
+ n Cl (CH2)4 C
C
O
Cl
O
(CH2)6 N
H
C
O
N
H 6C
(CH2)4 C
O
n
+ (2n - 1)HCl
Overral equation:
Nylon 6,6
6C

Physical properties
• Nylon 6,6 has a melting point of 265°C, it is most resistant to heat and
friction and enables it to withstand heat setting for twist retention.
• Its long molecular chain results in more sites for hydrogen bonds, creating
chemical “springs” and making it very resilient.
• It has a dense structure with small, evenly spaced pores. This means that nylon 6,6 is
difficult to dye, but once dyed it has superior color fastness and is less susceptible to
fading from sunlight and ozone.
• Nylon 6,6 has high tensile and high flexural strength; lower expansion; better
dimensional stability; and improved thermal conductivity and electrical
conductivity.

CHARACTERISTICS
 Variation of luster: nylon has the ability to be very lustrous, semilustrous
or dull.
 Durability: its high tenacity(measures the specific strength in N.m/Kg) fibers are
used for seatbelts, tire cords, other uses.
 High elongation.
 Excellent abrasion resistance.
 Highly resilient.
 High resistance to insects, fungi, animals, as well as molds,
mildew, rot and many chemicals.
 Used in carpets and nylon stockings.
 Melts instead of burning.

APPLICATIONS
1. Carpet fiber
2. Apparel
3. Airbags
4. Tires
5. Ropes
6. Conveyor Belts
7. Hoses
Nylon 6,6's longer molecular chain and denser structure qualifies it
as a premium nylon fiber, specified most often by professional
architects and designers for use in commercialsettings like offices,
airports, and other places that get a lot of wear and tear. It is also
anexcellent choice for residential carpet applications.

Preparation of phenol formaldehyde Resin
5/10/201
8
2

History
• The first phenolic resin was produced by poly condensation of phenol
with aldehyde in 1860.
• In 1860“VON BAYER” first reports the
reaction between phenoland aldehyde.
• The phenolic resin condensationwas used industrially in 1902 by
“BLUMMER” for production of novolac.

Introduction
• Phenolic resin is a poly-condensation product of phenols and
aldehydes, in particular phenol and formaldehydes.
• Phenolic resin is a heat cured plastic formed from a reaction of carbon
based alcohol and a chemical called aldehyde.
• Formaldehyde is a common raw material for this type of resin. the
resin is hard, heat resistant, and can be mixed with range of materials
for industrial and residual uses.
• Old phones were made of Bakelite , which is a phenolic resin.

Principle
The polymeric product obtain by condensation polymerization of
Phenol and Formaldehyde is called Phenol-formaldehyde resin.
The are structurally polydisperse compound.
Different end products are obtained depending on whether the
poly- condensation is carried out in acidic or basic medium of
phenol or formaldehyde in access.
 Reaction is generally carried out in aqueous medium.

Chemical Reaction
Phenol Formaldehyde resins are prepared by reaction of phenol with formaldehyde in the
presence of acidic or basic catalyst. The process may be carried out as follows;
• A mixture of phenol and formaldehyde are allowed to reactin
the presence of a catalyst i.e.Oxalic acidandsodium
hydroxide.
• The process involves formation of methylene bridges
inortho,paraorboth ortho and parapositions.
• This results in the formation of eitherNovolac(when P:F is
1:0.8 ) orResol(When P:F is 1:1.2).
Phen
ol
Formaldehyd
e

Novolac
Soluble in alcohol, lower ester, Ketone and dilute alkali.
Average MW is between 600- 1500.
Melting point is between 100⁰C and 140 ͦC.
 Thermoplastic. Usually obtain in acidic medium.
 Phenol functionality is ortho and para.
 Phenol: formaldehyde is 1:0.8
 Can be cross-linked.
 After heating and curing agent to novolacs, obtain Bakalite as a product.

Reaction is carried out in basic medium.
Not soluble after complete crosslinking.
Very high MW due to three dimensional crosslinking structure.
Degradation start at > 350⁰C.
Thermoset polymer.
Phenol functionality is ortho, meta, para.
Phenol : formaldehyde is 1:1.2
Already cross- linked.
After heating and in neutral or acidic condition obtain RESITE as
product
Resole

Chemical Reactions
Heat of reaction: 180
cal/g
1
2
Temperature:
Hydroxymethyl phenols will
crosslink on heating to
around 120 °C
By product: Water

65 g of Phenol
42g of 37% aqueous
formaldehyde
2g of oxalic acid
15ml of water
500ml beaker
STEP01
STEP
02
STEP03
Procedure

Mixture is refluxed for 45 min
WaterRemoval
Cooling
300ml water is added
Agitated thoroughly
Allowed to cool down
Liquid
Phenol
formaldehyde
Rigid and brittle Phenol
formaldehyde
Required
material
Final Product
Last STEP
5/10/201
8

Our preparedProduct
5/10/201
8
1
6

Properties:-
 Phenolic resins are hard, rigid and strong materials.
 They have excellent heat and moisture resistance.
 They have good chemical resistance.
 They have good abrasion resistance.
 They have good electrical insulation characteristics.
 They are usually dark coloured, pinkish brown.
 Low molecular weight grades have excellent bonding
strength and adhesive properties.

Applications
• Phenolic resin have good adhesive and bonding
properties.
• They are hard and infusible with good electrical
properties.
• Also used for the coating of wood.
• High resistance to heat, flammability, abrasion
resistance, water chemical and solvents.
1
7

UREA - FORMALDEHYDE
These resins are prepared by the reactions of formaldehyde with urea to give UF
resins.
preparation:- Urea and formaldehyde react with each other in neutral or acidic
conditions to give mono and dimethylol urea, which undergo further condensation
reactions to give linear, partialy cross-linked or fully cross- linked polymer.

Manufacturing of UF resins
i) Urea is dissolve in 36% w/w formalin, whose pH is adjusted to 8 with castic
soda(NaOH). The blending is carried out in stainless- steel reactor for about 30min
at 40 degree. The urea formaldehyde ratios in the range 1:1.3 to 1:1.15 are
normally employed. A solution at the end of this process contains urea
formaldehydes, mono- and di methylol urea.
ii) the cellulose fillers are incorporated in it using trough mixier. In ratio 2:1.
iii) The resulting wet base is then fed to turbine drier, at 100degree celcius for 2 hours.
iv) Addition of additives like stabilizers, accelerators are incorporated in dry mixer.
v) Then resultant mix is then ball-milled for 6-9 hours

Properties:-
Clear and colorless.
Better hardness and tensile strength.
Good solvent, grease and moisture resistance.
Excellent abrasion and resistance.
Good adhesives characteristics.

Applications:-
a). As adhesives for plywood and furniture;
b).for the finishing of cotton textiles.
c).They are also helpful for shrinkage control.
d). For making buttons and mugs.
d). For bottle caps and,
e). For coloured toilet seats.

 Rubber is a polymer, which is a word that is derived from the Greek
meaning “many parts”.
 Natural rubber is a naturally occurring polymer obtained from the latex of rubber
trees.
 Natural rubber (NR) is also known as cis-1,4-poly(isoprene).
 Natural rubber is found in the latex that comes from the rubber trees.
 It is collected in a cup mounted on each tree, by slashing the bark to reach the
latex vessels.
 The rubber latex is 25-45% of rubber.
 The commercial source of natural rubber latex is the Para rubber tree (Hevea
brasiliensis).

Preparation
Latex is diluted to contain 15-20% of rubber. After dilution it is filtered to eliminate any
dirt that may be present. It is then coagulated in a tank fitted with irregular partitions by
adding about 1kg acetic acid or formic acid per 200kg of rubber, to a soft white mass.
Sometimes, ammonium or potassium alum are also used as coagulants. After washing
and drying the mass of coagulated matter is subjected to any of the following process-
i).Crepe rubber- It is prepared by adding little sodium bisulfide to bleached the rubber
and then it is passed through a creeping machines so that coagulum is rolled out
into the sheet of about 1mm thickness, the sheet is then dried at 50degree in air.

ii).Smoked rubber- It is made by eliminating the bleaching with
sodium sulphite and rolling the coagulum into somewhat thicker
sheets having ribbed pattern on its surface. Ribbed surface pattern on
the sheet prevents them from adhering together on stacking. It also
facilitates consequent drying as it exposes greater surface area of the
sheet. The sheets are then dried in smoke houses at about 50 degree
in the smoke obtained from burning wood or coconut shells. The
rubber sheet thus obtained is translucent and amber in colour.

Drawbacks of Raw Rubber-
Natural rubber is useless as pure gold because of its following
drawbacks;
a. Raw or crude rubber become soft and sticky in hot summer, while in
cold weather it becomes hard and brittle.
b. It is weak, because of its low tensile strength(200kg/cm.squ).
c. It is attacked by oxidising agents (HNO3,conc H2SO4 etc).
d. In organic solvents it undergoes swelling and gradual disintregration
e. It is not durable.
To improve the properties of rubber, it is compounded with various
ingredients.

COMPOUNDING
 Rubber is always compounded with additives to satisfy the given
application in terms of properties, cost, and processability
 Compounding adds chemicals for vulcanization.
 Mainly used reinforcing filler used in NR is carbon black.
 Other additives include-antioxidants ,antiozonants colouring
pigments, plasticizers and softening oils, blowing agents in the
production of foamed rubber; and mold-release compounds.

Vulcanization of Rubber
 It consists of heating the raw rubber at 100-140 degree temperature
with sulphur.
 The sulphur combines chemically at the double bonds of different
rubber springs and provides cross –linking between the chains.
 This cross linking during vulcanization brings abouts a stiffening of the
rubber by anchoring and consequently preventing intermolecular
movement of rubber springs.
 The amount of sulfur added determines the extent of stiffness of
vulcanized rubber.
 For examples- ordinary soft vulcanized rubber(for tyres) contains 3-5%
sulfur, but hard rubber (for battery case)may contains as much as 30%
sulphur.

Unvulcanised rubber
vulcanized rubber

Synthetic Rubber
A synthetic rubber is any artificial elastomer. They are polymers synthesized from
petroleum byproducts. has many uses in the automotive industry for tires etc.

STYRENE RUBBER(GR-S or Buna-s or SBR)
Manufacture-
Butadiene (75%by weight) and styrene(25% by weight) are dispersed in
water with the help of an emulsifying agent (like soap). Subsequently,
emulsion polymerization is started with cumene-hydroperoxide initiator.
After the completion of polymerization, polymer styrene-butadiene rubber
is produced.

Since, SBR contains double bond so vulcanization can be done in the same
way as natural rubber either by sulphur or sulphur monochloride(S2Cl2). Less
sulphur and more accelerators are required for vulcanization. Carbon black
as reinforcing filler is essential to achieve good physical properties, like- High
strength.
Properties- SBR has the following characterstics:
a. High abrasion resistance,
b. High load bearing capacity,
c. resilience,
d. It swells in oils and solvents,
e. Low oxidation resistance, as it gets readily oxidised, especially in presence of
trace of ozone present in the atmosphere.
f. Vulcanization and compounded cold rubber has greater tensile strength and
greater abrasion resistance than the SBR or natural rubbers.

Aplications:-
SBR is used in following applications
a.Motor tyres,
b.Shoes soles,
c.Foot wears components,
d.Insulation of wires and cables,
e. Carpets backing,
f. Gaskets,
g.Adhesives and tank lining, etc

Nitrile Rubber (Buna-N or
NBR)
Manufacturing- To prepare Nitrile rubber, Butadiene(3% weight) and
acrylonitrile(1% weight) are mixed with water so as to get emulsion
which is stabilized by adding soap(emulsifying agent) by this technique
of emulsion polymerization, Nitrile rubber is manufactured

Compounding and vulcanization methods are similar to those of
natural rubber.
Properties:-
a. Due to the presence of cyano groups, nitrile rubber is less resistance
to alkalis(NaOH, KOH etc)than natural rubber,
b. As the acrylonitrile percentage is increased in nitrile rubber, its
resistance to acids, salts, oils, solvents etc But the low temperature
resilience suffers. The nitrile rubber shows excellent resistance to oils,
chemicals, aging(sun light).
c. Compared to natural rubber, nitrile rubber(vulcanized) has more heat
resistance and it may be exposed to high temperature.
d. It has good abrasion resistance, even after immersion in gasoline or
oils.

Advantages:-
Nitrile rubber is used for-
a. Conveyor belts,
b. Lining of tanks,
c. Printing rollers,
d. Oil resistance foams,
e. Automobiles parts and aircrafts components’
f. Adhesives.

unit 4 polymer BT101_1674199439.pptx

unit 4 polymer BT101_1674199439.pptx

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