educational for chemistry students about polymer chemistry
13
Polymerization Polymers are macromolecules of high molecular weight which are formed by linkage between large numbers of small molecules called monomers, e.g., polyethylene is made up of the monomers ethylene. H 2 C CH 2 n CH 2 CH 2 n There is no limit to theoretical length of the polymer, but the polymer ceases to grow for many practical reasons. The number of repeating units in a polymer is called the “degree of polymerization”. 2 2 CH 2 CH 2 n Ethylene (monomer) Polyethylene (polymer) Plastic & Polymer The words polymers and plastics are often taken as synonymous The polymer is the pure material which results from the process of polymerization. When additives are present that the term plastic is applied. Functionality of a Monomer Functionality means the number of bonding (or reactive) sites in a given molecule. The number of reactive functional groups (like –NH 2 ; -COOH, -OH; -NCO; -SH; etc) per molecule of the compound defines its functionality. Q. Classify the following on the basis of their functionality: i) Ethylene glycol ii) Vinyl chloride iii) Lactic acid Compound Chemical Formula No of double bonds per molecule No of functional groups present per molecule Functionality -OH -COOH -Cl Ethylene glycol - 2 Bifunctional Vinyl chloride 1 - - 1 Bifunctional Lactic acid - 1 1 - Bifunctional CH 2 CH 2 OH OH CH 2 CH Cl CH 3 CH(OH) COOH Skeletal Structure Linear Polymers: A chain with two ends i.e. each monomeric unit is linked with two monomeric units on either side, forming a continuous chain. Branched Polymers: In some cases, while the polymer chain is growing in a linear manner, some side growth also takes place from the main chain.
Transcript
Polymerization
Polymers are macromolecules of high molecular weight which are
formed by linkage between large numbers of small molecules called
monomers, e.g., polyethylene is made up of the monomers ethylene.
H2C CH2n CH2 CH2 n
There is no limit to theoretical length of the polymer, but the polymer
ceases to grow for many practical reasons. The number of repeating
units in a polymer is called the “degree of polymerization”.
Plastic & PolymerThe words polymers and plastics are often taken as synonymous
The polymer is the pure material which results from the process of polymerization.
When additives are present that the term plastic is applied.
Functionality of a MonomerFunctionality means the number of bonding (or reactive) sites in a given
molecule. The number of reactive functional groups (like –NH2; -COOH,
-OH; -NCO; -SH; etc) per molecule of the compound defines its functionality.
Q. Classify the following on the basis of their functionality: i) Ethylene glycol
ii) Vinyl chloride iii) Lactic acid
Compound Chemical Formula
No of double bonds permolecule
No of functional groups present per molecule
Functionality
-OH -COOH -Cl
Ethylene glycol
- 2 Bifunctional
Vinyl chloride 1 - - 1 Bifunctional
Lactic acid - 1 1 - Bifunctional
CH2
CH2
OH
OH
CH2 CH Cl
CH3
CH(OH)
COOH
Skeletal StructureLinear Polymers: A chain with two ends i.e. each monomeric unit is linked
with two monomeric units on either side, forming a continuous chain.
Branched Polymers: In some cases, while the polymer chain is growing in aBranched Polymers: In some cases, while the polymer chain is growing in a
linear manner, some side growth also takes place from the main chain.
Skeletal StructureCross linked Polymers: During polymerization, a large number of branchedpolymer molecules may be formed and on further polymerization , the sidechain from one molecule could possibly interact with those from theneighbour ones.
Steriochemistry of PolymerIsotactic Polymers: They have all the groups in one side of the polymeric backbone
and the monomers are joined in a regular head to tail arrangement e.g. Natural
Rubber.
Syndiotactic Polymers: They have similar head to tail arrangements but here Y
groups appear on opposite sides of polymer backbone alternately e.g. Gutta Percha.groups appear on opposite sides of polymer backbone alternately e.g. Gutta Percha.
Atactic Polymers: They have Y groups arranged randomly along the polymeric
backbone and the material is soft, elastic, rubbery e.g. Polypropylene.
Classification of PolymerAddition Polymer: When the monomer units are repeatedly added to form long chains
without the elimination of any molecules of by product, the product formed is called
addition polymer and the process involved is called addition polymerization. The molecular
mass of the addition polymer is an integral multiple of that of the monomer unit.
Addition and Condenstion PolymerAddition Polymerization Condensation Polymerization
It requires the presence of double
bond in the monomer.
It requires two reactive functional groups to
be present at both ends of the monomer.
No by-product is formed Generally a by-product is formed
Homo-chain polymer, generally a Hetero-chain polymer either thermo plasticHomo-chain polymer, generally a
thermoplastic is obtained.
Hetero-chain polymer either thermo plastic
or thermoset can be obtained.
The growth of chain is at one active
center.
The growth of chain occurs at minimum of
two active center.
Examples of Addition polymerization:
Polymerization of ethylene to form
polyethylene (PE)
Examples of Condensation polymerization:
Condensation polymerization of
caprolactum to form nylon-6.
Molecular Weight of PolymerMolecular weight of a polymer increases continuously during thepolymerization reaction depending upon the simple molecular unitsjoined together to form macromolecules. There are two types ofaverage molecular weight of polymers.
Number average molecular weight: It is defined as the total weight (w)of all molecules in a polymer sample divided by the total no of molesof all molecules in a polymer sample divided by the total no of molespresent. Suppose a sample is made up on a fraction consisting of N1
moles of molecular weight M1, and N2 moles of molecular weight M2,and so on, then,
��=
++++++=
i
iin N
MN
NNNMNMNMN
M...........
...........
321
332211
nM is generally determined by osmotic pressure measurement
Molecular Weight of PolymerWeight average molecular weight: It depends upon the masses of the
material in different molecular weight fraction. In this method, while
taking average, the molecular weight of each species is multiplied by
the weight of the species and not the number.
......................332211
++++++=
mmmMmMmMm
M w
But m1 = N1M1; m2 = N2M2; and so on where N1, N2...... are no of mole
of molecular weight M1 and M2 respectively. Hence
wM is generally determined by techniques like ultracentrifugation
...........321 +++ mmmw
��=
++++++=
ii
iiw MN
MN
MNMNMNMNMNMN
M2
332211
233
222
211
......................
Thermoplastics
� Linear or branched polymers which can be melted when
heat is applied.
� Can be molded into any shape with processing techniques
such as injection molding or extrusion.
� Most common “plastics”
� Plastics: bottles, grocery bags, water piping, rope, fishing
� Network polymers in which chain motion is greatly
restricted by a high degree of crosslinking.
� Cannot be reshaped once formed.� Cannot be reshaped once formed.
� Uses: High temperature electrical applications, super glue,
counter top laminates, epoxy resins, tires (vulcanized rubber)
� Cannot be recycled (burn/scorch with heat)
� Natural thermosets: Vulcanized rubber
Thermoplastic and ThermosetsThermoplastics Thermosets
Linear polymer Cross-linked polymer
Weak van der Waals intermolecular
forces and thus soften/melt on
heating.
Chemical cross-links make them
infusible materials. Do not melt on
heating.heating. heating.
Molten polymer can be moulded in
desired shape.
Crosslinking is usually developed at
the time of moulding where they
harden irreversibly.
Examples are Polystyrene, PVC,
SBR, Teflon, PMMA, Terylene.
Examples are Glyptals, Epoxy
polymers, Formaldehyde resin.
Types of Ploymer� Resins: Resins are the basic binding material of the plastic and are present as a
major constituent (40-80%) of the plastics. The nature of the resin used in plastic
determines the type of treatment which is necessary for the moulding process.
� Fillers: The fillers impart certain specific properties of the plastics, beside
reducing cost of the plastics per unit weight. The common fillers are quartz and
mica (to increase hardness), inorganic fillers like asbestos are also used. Besidemica (to increase hardness), inorganic fillers like asbestos are also used. Beside
the above fillers the other fillers used are, cotton, cornhusk, carbon black, saw
dust etc. the amount of filler can be 40-50% of the plastic material.
� Plasticizers: This improve the plasticity and flexibility of the polymers. The
plasticizing property of the plasticizers is believed to be due to the partial
neutralization of the intermolecular forces of attraction in the resin molecules.
Some commonly used plasticizers are vegetable oils, camphor's, etc.
Homopolymer and Co-polymerHomopolymer Co-polymer
Homopolymer is a polymer where it has
only one type of monomer.
A co-polymer is a polymer with two different types
of monomer units.
Since there are only one type of
monomer so there is no variation in
joining
Since there are various ways of joining the two
monomers, there are different types of copolymers.
Polystyrene is a homopolymer where the
repeating unit is styrene residues.
Commercially relevant copolymers include ABS
plastic, styrene-acrylonitrile, etc.
Polypropylene is produced in both homopolymer and copolymer grades.
Homopolymer polypropylene is stronger
and stiffer than copolymer.
Copolymer polypropylene is a bit softer, but it is
Write the chemical structures and use (in each case) of the following macromolecules.i) Poly- ε ε ε ε-Caprolactum ii) Polyethylene terephthalateiii) Cis-1,4-polyisoprene crossed linked through a non-metal.
Solution: i) Poly- ε ε ε ε-Caprolactum
It is used in the manufacture of tyre
cords
ii) Polyethylene terephthalate
It is used as a blend with cotton in
C
O
HN (CH2)5 n
CH2 CH2 O C
O
C
O
OIt is used as a blend with cotton in
clothing.
iii) Cis-1,4-polyisoprene crossed linked
through a non-metal.
It is used in making gloves, rubber bands
and tubes
CH2 CH2 O C C O
n
PolycarbonatePreparation: Polycarbonate received their name because they are polymer having
functional group lined together by carbonate groups (-COO-) in a long polymeric
chain. It can be synthesized from bisphenol A and phosgene (carbonyl dichloride,
COCl2)
CCH3
CH3
HO OH + Cl C
O
ClNaOH
CCH3
CH3
O C
O
O
n3
n
Properties: The outstanding feature of this plastic is their extreme toughness and is
known as unbreakable. They are transparent and have good temperature resistance.
This polymer is highly transparent to visible light and has better light transmission
characteristic than many kind of glass.
Application: Typical application include, in the manufacturing of CD, DVD, blue ray
discs, lighting lenses, eye glasses, laptop cases, riot shield, street lamp covers etc.
Polyethylene terephthalate (PET)Preparation: It can be synthesized by the esterification reaction between terephthalic
acid and ethylene glycol with water as a by-product.
C +O
OHC
O
HO HOOH
- H2OC
O
OC
O
CH2 CH2 On
Properties: It is a thermoplastic polymer resin of the polyester family. Depending on
its processing, polyethylene terephthalate may exist both as an amorphous
(transparent) and as a semi-crystalline material. While most thermoplastics can, in
principle recycled, PET bottle recycling is more practical than many other plastic
applications.
Application: It is used in synthetic fibers, beverage, food and other liquid containers
PolyurethanePreparation: Polyurethane is derived from a chemical reaction of a diisocyanate with
a polyol.
nC
OHN
H2C
HN C
O
O OH2C
H2C
O C NH2C N C O HO OH
H2C
H2C+
Properties: The important features of polyurethane are, they have outstanding low
temperature performance, very good tear resistance, excellent mechanical properties
combined with a rubber like elasticity.
Application: Polyurethane is plastic materials which exist in various forms and is a
material of choice for a broad range of end user applications such as: Insulation of
refrigerator and freezers; Cushioning for furniture and automobile seat; Composite
wood panel; Roller and tyre; Shoe soles; Mattresses, Car parts; Adhesive etc.
Polypropylene or polypropene (PP)Preparation: Polypropylene is obtained by polymerizing propylene in presence of
Ziegler- Natta Catalyst i.e., organo metallic halide with transition metal halide.
C C
HCH3
H H
n PolymerizationC C
CH3
H
H
Hn
Properties: Polypropylene is also an isotactic, highly crystalline polymer. It is superior
to polyethylene w.r.t. resistance to chemicals, hardness, strength, moisture proofing
quality etc. It is lightest among all high polymers.
Application: It is used in a wide variety of applications, including packaging, textiles
(e.g. ropes, thermal underwear and carpets), stationery, plastic parts and reusable
containers of various types, laboratory equipment, loudspeakers, automotive
components, and polymer banknotes.
Polyvinyl Chloride ( PVC )Preparation: It is commonly known as PVC and is obtained by the polymerization of
vinyl chloride. The method consists in introducing vinyl chloride and water (1 : 1)
along with persulphate catalyst at 40-50 oC.
Properties: PVC is a colorless, odorless, non-flammable, chemically-inert powder. It
C C
HCl
H H
n PolymerizationC C
Cl
H
H
Hn
Properties: PVC is a colorless, odorless, non-flammable, chemically-inert powder. It
contains 53- 55% Cl2 and softens at around 80�C. It is resistant to water, light, O2,
inorganic acids and alkalies, oil, petrol etc., but soluble in hot chlorinated
hydrocarbons.
Application: It is the most widely used plastic. It has high rigidity and chemical
resistance but brittle, so, its use is mainly in making cables, water hoses, toys, rain
coats, rexin, pipes of petroleum industry, floor covering, refrigerator components,
tyres, cycles and motor cycle mudguards etc.
Polytetrafluoroethylene (PTFE) or (TEFLON)Preparation: It is obtained by polymerization of water-emulsion of tetrafluoro-
ethylene, under pressure and in presence of benzoyl peroxide as catalyst.
Properties: Due to the presence of highly electronegative fluorine in the regular
polymer structure of TEFLON strong inter chain forces are present which give the
material extraordinary properties like extreme toughness, high softening point
C C
FF
F F
n PolymerizationC C
F
F
F
Fn
material extraordinary properties like extreme toughness, high softening point
(350°C), high chemical resistance, low coefficient of friction and waxy touch, good
mechanical and electrical properties. Due to all these qualities, the polymeric material
can be machined. It softens at about 350 °C, hence at this high temperature it can be
moulded applying high pressure.
Application: I t can be used for insulating motor, transformers, cables, wires etc. Non-
stick cookware coatings are made of TEFLON. It can also be used for making gaskets,
pump parts, tank linings, pipes and tubes for chemical industry, non-lubricating
bearings and to make non-reactive coating.
Nylon6,6Preparation: Nylon 6,6 is made of hexamethylenediamine and adipic acid, which give
nylon 6,6 a total of 12 carbon atoms in each repeating unit, and its name.
Properties: Nylon 6,6 has a melting point of 265�C, high for a synthetic fiber. This fact
H2N (CH2)6n NH2 HOOC (CH2)4n COOH+
HN (CH2)6 C (CH2)4 C
O
HN
O
+ 2n H2O
Nylon-6,6
Hexamethylene diamine Adipic acid
n
Properties: Nylon 6,6 has a melting point of 265°C, high for a synthetic fiber. This fact
makes it resistant to heat and friction. Its long molecular chain results in more sites
for hydrogen bonds, creating chemical “springs”, 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 colorfastness and is less susceptible to fading
from sunlight and ozone and to yellowing from nitrous oxide.
Application: The common application include Carpet fiber, Apparel, Airbags, Tires,
Zip Ties, Ropes, Conveyor Belts, Hoses, etc.
Polymer and their monomerPolymer Monomer
Natural rubber Isoprene (2-metyl-1, 3-butadiene)
Neoprene Chloroprene
Polyacrylonytrile (PAN) or Orlon Vinyl cyanide (acrylonitrile)
Styrene-butadiene rubber (SBR) or Buna SPreparation: This variety is the most important synthetic rubber and it is obtained
by copolymerization of butadiene and styrene.
xn CH2 CH CH CH2 + n
CH CH2
Copolymerization
CH2 CH CH CH2 CH2CHx n
butadienestyrene
styrene butadiene rubber
Properties: SBR is similar to natural rubber in processing character and also asfinished product. It possesses high resilience and good and tough mechanicalproperties. But unfortunately it is easily attacked by oxidizing agents, mainly ozone. Italso swells in organic solvents. I t can be vulcanized as natural rubber.
Application: It is the most widely used plastic. It has high rigidity and chemicalresistance but brittle, so, its use is mainly in making cables, water hoses, toys, raincoats, rexin, pipes of petroleum industry, floor covering, refrigerator components,tyres, cycles and motor cycle mudguards etc.
Nitrile rubber (NBR) or Buna N or Gr-APreparation: It is prepared by the copolymerization of butadiene and acrylonitrile inemulsion system.
Properties: 1. Due to the presence of cyano groups, nitrile rubber is less resistance toalkalis than natural rubber.
2. Excellent resistance to oils, chemicals, aging.
3. Compared to natural rubber, nitrile rubber (vulcanized) has more heat resistanceand it may be exposed to high temperatures.
4. It has a good abrasion resistance, even after emersion in gasoline or oils.
Application: It is widely used in conveyer belts, lining of tanks, gaskets, prinitingrollers, oil resistance foams, automobile parts and high altitude air-craft components,hoses and adhesives.
Synthetic RubberPolyisoprene: It is made byZieglar Natta polymerization ofisoprene. This is a rare exampleof a natural rubber that can bemade from isoprene.
Polyisobutylene: It is synthetic rubberand is also called butyl rubber. It is
n Zieglar-Natta
Isoprene
C C
CH
H
C
H
HH
CH3
PolymerizationC
H3C
C
CH2
H
CH2
n
Poly isoprene
n Cationic vinylC C
H CH3
Polymerization
H CH3
made from the monomer isobutylene bycationic vinyl polymerization.
n
IsobutyleneCH3
H
Polymerization
Poly isobutyleneH CH3 n
Polybutadiene: It is made byZieglar Natta polymerization ofbutadiene. It is very similar tonatural rubber and is good foruses which require exposure tolower temperature.
n Zieglar-Natta
Butadiene
C C
CH
H
C
H
HH
H
PolymerizationC
H
C
CH2
H
CH2
n
Poly butadiene
Vulcanization of RubberIt consists of heating rubber with 1-3% of sulphur, an accelerator, inert filler and anantioxidant. Sulphur helps to cross links the parallel polymer chains which contain upto eight sulphur atoms. The sulphur combines chemically at the double bonds in therubber molecule bringing about excellent changes in its properties. The process wasdiscovered by Charles Goodyear in 1839.
Properties of Vulcanized Rubber:
1. It has good tensile strength andextensibility.
2. Resistance of vulcanized rubber getsmuch improved.
3. Water absorption capacity of vulcanized rubber is considerably lowered.
4. It has a better electrical insulator, although it tends to absorb small amount of water.
5. Vulcanized rubber has much lower elasticity.
6. Vulcanized rubber is resistance to organic solvents such as benzene, CCl4, etc.
Comparison of Natural and Synthetic RubberProperty Natural Rubber Synthetic RubberTensile Strength Low High
Chemical Resistivity Low-gets oxidized even in air High-not oxidized in air
Action of Heat Cold condition it is hard and
brittle, at higher temperature
Can withstand effect of heat
over a range of temperature
With organic solvents Swells and dissolves Does not swell and dissolve
Ageing Undergoes ageing quickly Resist ageing
Elasticity On increased stress
undergoes permanent
deformation
Has high elasticity
Synthetic rubber has slightly modified structures from natural rubber and exhibitproperties that are more conductive for their technical uses.
Conductive PolymersConducting polymers are mostly organic polymer and as the name suggest
they conduct electricity. Such compounds may be true metallic or
semiconductors. Polyacetylene was first conducting polymer, synthesized by
Natta way back in 1958. It was found to conduct in the range of 7X10-11 to
7X10-3 Sm-1 depending upon how the polymer was processed and
manipulated.
It is a conducting polymer because the conjugated double bond in
polyacetylene make possible the process of conducting electricity down its
backbone after several electron are added or removed from the backbone.
HC CHnn
Classification of Conductive PolymersElectrically conducting polymers can be classified into following groups:
Applications of Conductive PolymersAlthough several conducting polymers have been prepared, it was soon realized that
they cannot compete with metals in traditional electrical applications, like wiring,
transmission cables etc.
Polymeric Batteries: One of the first applications of conducting polymers, that was
the focus of attention world-wide, was that of light-weight batteries.
Electrochromic Displays: Electrochromic display is another interesting applicationElectrochromic Displays: Electrochromic display is another interesting application
which utilizes the electrochemical doping and undoping of conducting polymers.
Electroluminescence: Light emission is observed when a voltage is applied to a thin
layer of a conductive organic polymer film. This property has led to the development
of flat panel displays using organic LEDs, solar panels, and optical amplifiers.
Other use: Other use include Electromagnetic shielding, Antistatic clothing, Printed
circuit boards, Conducting adhesives, etc.
Conducting PolymersPolypyrrole: A polypyrrole (PPy) is a chemicalcompound formed from a number of connected pyrrolering structures. Polypyrroles are also called pyrroleblacks or polypyrrole blacks,
Polythiophene: Polythiophenes (PTs) result from thepolymerization of thiophenes, a sulfur heterocycle, thatcan become conducting when electrons are added or
N
N
H
H
n
S
S can become conducting when electrons are added orremoved from the conjugated p-orbitals via doping.
Polyaniline: The discovery of electrically conductive polymer compositions based onpolyaniline provides conductive materials, which are soluble in selected organicsolvents. These materials are which are melt processable and exhibit good ambientstability characteristics. environmentally and thermally stable.
NN NH NHn
n
Phenol-formaldehyde ResinPhenol formaldehyde resins (PF) include synthetic thermosetting resins such asobtained by the reaction of phenols with formaldehyde. They are better knownhowever for the production of molded products including pool balls, laboratorycountertops, and as coatings and adhesives. In the form of Bakelite, they are theearliest commercial synthetic resin.
Urea-formaldehyde ResinIt is a non-transparent thermosetting resin or plastic, made from urea and
formaldehyde heated in the presence of a mild base such as ammonia or pyridine.
These resins are used in adhesives, finishes, MDF, and molded objects.
Melamine-formaldehyde ResinMelamine resin or melamine formaldehyde (also shortened to melamine) is a hard,thermosetting plastic material made from melamine and formaldehyde bypolymerization. It is then used to cross-link with alkyd, epoxy, acrylic, and polyesterresins, used in surface coatings. There are many types, varying from very slow to veryfast curing. It was initially discovered by William F. Talbot.
Glyptal ResinGlyptal is a general name of all polymers obtained by condensation of di-basic acidsand polyhydric alcohols. The alkyd resins are modified either by oil or fatty acids. Itdissolved in suitable solvents and the solution on evaporation leaves a tough and nonflexible film. It is used in adherent paints, lacquers and building materials like asbestosand cement.
Biodegradable PolymersBiodegradable polymers are those polymers which gets decomposed by the
process of biodegradation. Biodegradation is defined as the process carried
out by biological systems (usually fungi or bacteria) wherein a polymer chain
is cleaved via enzymatic activity.
A biodegradable polymer is one that would be decomposed by microorganism.
Though most commercial polymer in use today are non-biodegradable,Though most commercial polymer in use today are non-biodegradable,
interest among the scientists and researcher is to produce cheap biodegradable
polymers with desired properties to replace the existing material in use.
Biodegradable polymer degrade mainly by enzymatic hydrolysis and in some
cases by oxidation. Biodegradable synthetic polymers mostly have functional
groups prevalent in proteins, polysaccharides and lipids.
Poly(hydroxybutyrate-co-ββββ-hydroxyvalerate), PHVBPoly(hydroxybutyrate-co-ββββ-hydroxyvalerate), PHVB, is a biodegradable
polymer made by the condensation of 3-hydoxybutanoic acid and 3-hydroxy-
pentanoic acid.
COOHCH2CHHO
CH3
n + n HO CH
CH2
CH2COOH
CH3
It is used as packaging material, in orthopedic device and in controll drog
release .
COOHCH2CHHOn + n HO CH CH2COOH
CCH2CHO
CH3
O CH
CH2
CH2
CH3
C
OO
n
Other Example of Biodegradble PolymerPolyglycolic acid and Polyactic acid are the examples of biodegradable
polymer. Nylon-2-nylon-6, an alternating polyamide copolymer of glycine and
6-aminocaproic acid is also a biodegradable polymer.
CCH2O
O
n CCHO
O
n
CH3
CCHHN
CH3
Polyglycolic acid Polyactic acid
O
NH (CH2)5 C
O
n
Nylon2-nylon-6
Types of Polymerization
H
I
G
� Addition polymerization:
The product polymer is exact multiple of the original monomeric molecule e.g.,
polythene from ethene.
� Condensation polymerization:
Combination through different functional groups of monomers with elimination
H
L
I
G
H
T
of small molecules like H2O.
� Copolymerization:
Joint polymerization of two or more types of monomers. As for example SBR.
Ans: It is the number of bonding sites of monomer.
Q. When is vulcanization done? Mention some of the uses of vulcanized rubber.
Ans: Vulcanization is done after shaping the article. The shaping is done with raw
rubber along with suphur and other ingredients like accelerators, fillers etc.
Uses: Vulcanized rubber is used in vehicle tyres, hose, conveyer belt, electrical
insulation.
Q. What is the basic difference between nylon 6 and nylon 6 6 ?
Ans: Nylon 6 is an additional polymer whereas nylon 6 6 is a condensation polymer.Ans: Nylon 6 is an additional polymer whereas nylon 6 6 is a condensation polymer.
In nylon 6 , the composition of the monomer is the same as that of the polymer, but
nylon 6 6 is formed with the elimination of water molecules.
Q. Differentiate between a homopolymer and copolymer?
Ans: A homopolymer consists of many identical monomer units whereas a copolymer
consists of monomers of different chemical structures.
Q. What is copolymerization?
Ans: Copolymerization is the point polymerization of two or more monomers, e.g.,
butadiene and styrene to yield G R- S rubber.
Q. What is an elastomer?Ans: Any rubber- like elastic polymer, which can be stretched to thrice its size and afterremoval of the stretching force it returns to its original shape is called an elastomer.Q. Why thermosetting plastics cannot be reused?Ans: In thermosetting plastics, the monomers are bound to each other by strongcovalent bonds, which cannot be broken on heating. Thus by heating it cannot besoftened to reshape and reuse.Q. What is natural rubber and what is gutta-percha?Ans: Natural rubber is long-coiled chains of poly cis-isoprene and gutta-percha is hornyand tough form of poly trans-isoprene.and tough form of poly trans-isoprene.Q. Why is teflon highly chemical resistant?Ans: In teflon the most electronegative element F contributes to the strong attractiveforce within the chains and hence is non-reactive towards other chemicals.Q. What do you mean by biodegradation of polymers ?Ans: . Biodegradation is a process by which refuse mixes with environment bymicroorganisms. This biodegradation process is completely absent in the case of highpolymers. Development of biodegradable polymer ‘biopol’ is now a challenge toscientists. Polyhydroxybutyrate is a ‘biopol’ which degrades within a few months in soilbut it is too costly to be used very soon.
