investigatory of chemistry on polymers

1. CHEMISTRY INVESTIGATORY PROJECT
POLYMERS
ROLL NO:- CLASS :- 12
SUBMMITED BY:- SUBMMITED TO:-
VINAY KUNTAL MR. SHARMA SIR

2. ACKNOWLEDGEMENT
I wish to express my deep gratitude and sincere thanks to the
Principal Mr. MOHAN for his encouragement and for all the
facilities that he provided for this project work. I sincerely
appreciate his magnanimity by taking me into his fold for which
I shall remain indebted to. I extend my hearty thanks to Mr.
SHARMA SIR Chemistry teacher, who guided me to the
successful completion of this project. I take this opportunity to
express my deep sense of gratitude for her invaluable
guidance, constant encouragement immense motivation which
has sustained my efforts at all the stages of this Project work. I
can’t forget to offer my sincere thanks to parents and also to
my classmates who helped me to carry out this project work
successfully and for their valuable advice and support which I
received from them time to time.

3. CERTIFICATE
This is to certify that this “Chemistry Investigatory Project”
on the topic “POLYMERS” has been successfully completed
by VINAY KUNTAL of class XII – B under the guidance of
Mr. SHARMA SIR in particular fulfillment of the curriculum
of Central Board of Secondary Education {CBSE} leading to
the award of annual examination of the year 2017-18.
---------------------------
Signature
Mr. Sharma Sir

4. POLYMERS
Polymersare large moleculescomposed of repeated chemical units. The
smallest repeating unitis called a mer. The term polymer isderived from
the Greek words poly and mersmeaning"many parts." Linear polymersare
like ropes. For a polymer chain of 10,000units(atypical length), a
standard half-inch-thick rope would be about 128 meters(140 yards)long
to representthe length-to-thickness ratio. Polymersare synthesized
naturally and artificially to perform a widevariety of specialized tasks.
BASIC POLYMER SCIENCE
A polymer isgenerally described in terms of a single repeat unit, such as
the followingexample:
Figure 1.
The number of repeat unitsin a chain is called the degreeof polymerization
(DP)or chain length. Thus, a poly(propylene)chain 5,000 unitslongwould
have a DP of 5,000 and an "n"valueof 5,000. Becausemostpolymer
mixturescontain chains of varyinglengths, the chain length is often
referred to in terms of average chain length or average DP.
At either end of the polymer chain are end groups. (Becausethe chain is
often thousandsof units long, the end groupsare usually omitted.)For
(poly)propylene the repeatingcarbons (C-C-C-C-C-C-C)form the polymer
backbone and representthe atoms that connect the chain together. In vinyl
polymers, so called because they are generally derived from substituted
vinylreactants or monomers(Figure2), the polymer backbone is
composed of only carbon atoms. An exampleis poly(propylene), whichhas
fivemers represented .
.
Condensation polymer backbonesincludenon-carbon atoms. For example,
polyesters have oxygen atoms and nylons have nitrogen atoms in the
backbone in addition to carbon atoms .

5. Unsymmetricalreactants, such as substituted vinylmonomers, reactalmost
exclusively to give what are called "head-to-tail" productswherethe
substituents occur on alternative carbon atoms:
Figure 5. –CH 2 –CHX–CH 2 –CHX–CH 2 –CHX–CH 2 –CHX–
Occasionally a "head-to-head, tail-to-tail" configuration occurs. For most
vinylpolymersthis structureoccurs less than 1 percentof the time in a
random manner throughoutthe chain.
Figure 6. –CH 2 –CHX–CHX–CH2 –CH 2 –
Even with the head-to-tail configuration, a variety of structuresare
possible. These includea simplelinear homopolymer structure.
Copolymersarepolymersderived from two differentmonomersSaran, a
componentof Saran Wrap, is oneexample . Other examples of copolymer
structuresare depicted in Figure
Some linear chains have extensions (beyond the substitution) coming off
the polymer backbone. These extensions are called branches and influence
a polymer'sproperties. Branchesmay be long or short, frequentor
infrequent. For example, so-called low density polyethylene(LDPE)has
between forty and one hundred shortbranches for every 1,000 ethylene
units, whereas high density polyethylene(HDPE)has only one to six short
branches for every 1,000 ethyleneunits Branchingdiscouragesthe chains
from fitting close together so that the structurewill be amorphous with
relatively large amountsof empty space. Regular structures with little or no
branching allow the polymer chainsto fit close together, forminga
crystalline structure. Crystallinestructuresare generally stronger, more
brittle, of higher density, moreresistant to chemical penetration and
degradation, less soluble, and have higher melting points. For example,
HDPE has a density of 0.97 gram per milliliter and a melting point of about
130°C (266°F), whereasLDPE hasa density of about 0.92 gram per
milliliter and a melting pointof about 100°C (212°F).

6. Polymer chains can be connected to oneanother chemically or physically,
much like a knot can connect two pieces of string. These connections are
called crosslinks and cause the connected chains to act as a single unit
Some materials can have only a few crosslinks, such as permanentpress
materials where the fabric contour is locked into place with crosslinks.
Others materials such as Bakelite and ebonite are heavily crosslinked;
these are hard, brittle, non-flexible materials.

7. PHYSICAL PROPERTIES OF POLYMERS
The propertiesof polymersare dependenton many factorsincludinginter-
and intrachain bonding, the natureof the backbone, processing events,
presence/absence of additives includingother polymers, chain size and
geometry, and molecular weight distribution.
While most materials have melting/freezingand boiling/condensing
points, polymers do not boil because the energy necessary to puta polymer
into the vapor state is greater than the bond energies of the atoms that hold
the polymer together, thus they degrade prior to boiling. In order for a
polymer to be flexible, its variousunitsor segments mustbe able to move.
The glass transition temperature(T g ) is the temperaturewhere polymer
unitsor segments can movebut the entire chain cannot. Mostvinyl
polymershaveT g valuesbelow room temperatureso that they appear to
be flexible and act as rubber and plastic materials. Most condensation
polymershaveT g valuesabove room temperatureand are used as hard
plastics and fibers. The temperaturewhere entire chain movementoccurs
is called the melting point (T m ) and is greater than the T g .
Many polymersarethemselves brittle at room temperature. For these
polymersto become morepliable, additives called plasticizers that allow
segmental mobility, and consequently segmental flexibility, are added. For
synthetic polymerssuch as poly(vinylchloride)(PVC)
and polystyrene plasticizersare added that allow the polymersto be
flexible.
The inflexible regionsof a polymer, suchas crystalline regions, are often
referred to as "hard" regions. Conversely, the flexible regions of a polymer,
where segmental mobility occurs, are referred to as "soft" regions. This
combination of hard and soft can be illustrated with so-called segmented
polyurethanes.The urethaneportion of such polymersis involved in
hydrogen bondingand is considered "hard,"while the polyether portion,
flexible at room temperature, is considered "soft." These segmented
polyurethanesaresold under anumber of trade namesincludingSpandex.

8. HISTORY OF SYNTHETIC POLYMERS
While polymersform the basis of life, the history of synthetic polymersis
relatively recent. Someof the key polymersthat have been developed since
the early daysof polymer science include:
Vulcanized rubber. In the mid-1800s, American scientistCharles
Goodyear began workingwith rubber to try to make it more temperature
stable. After many unsuccessfulattempts, he accidentally allowed a mixture
of sulfur and pre-rubber to touch a hot stove. The rubber did not melt but
only charred a little. By 1844 Goodyear had been given a patent for a
process he called "vulcanization"after the Roman god of fire, Vulcan.
Vulcanization is the crosslinking reaction between the rubber chains and
the sulfur.
Bakelite. After years of work in his chemistry lab in Yonkers, New York,
Leo Baekeland announced in 1907thesynthesis of the first truly synthetic
polymericmaterial, later dubbed "Bakelite." It was generally recognized by
leading organic chemists of the nineteenth century that phenolwould
condensewith formaldehyde, butbecause they did not understand the
principlesof the reaction, they produced uselesscrosslinked materials.
Baekeland'smain projectwas to make hard objects from phenol and
formaldehydeand then dissolvethe productto reform it again in a desired
shape. He circumvented the problem by placingthe reactants directly in a
mold of the desired shape and then allowingthe reactants to form a hard,
clear solid—Bakelite .It could be worked (i.e., cut, drilled, and sanded), was
resistant to acids and organic liquids, was stable at high temperatures, and
did not break down when exposed to electrical charge. By addingdyesto
the starting materials the objects became available in differentcolors.
Bakelite was used to make bowling balls, phonographrecords, telephone
housings, cookware, and billiard balls. Bakelite also acted as a binder for
textiles, sawdust, and paper, formingawide rangeof composites including
Formica laminates. Many of these combinationsare still in usein the
twenty-firstcentury.

9. Neoprene. Chemist and Catholic priest JuliusA. Nieuwland did extensive
work in the 1920son acetylene. Hefound that acetylene could be madeto
add to itself formingdimersand trimers. Arnold Collins, a chemist at the
DupontCompanyin the lab of Wallace Carothers, continued work on the
project and in 1930 ran thereaction described by Nieuwland, purifyingthe
reaction mixture. He found asmall amountof material that was not
vinylacetyleneor divinylacetylene. After setting the liquid aside, it
solidified into a material that seemed rubbery and even bounced. This new
rubber was given the name Neoprene.Neoprenehasoutstanding
resistance to gasoline, ozone, and oil in contrast to naturalrubber and is
used in a variety of applicationsincluding electrical cable jacketing,
window gaskets, shoe soles, industrialhose, and heavy-duty drivebelts.
Nylon. In the early 1930sWallaceCarothersand his team of chemists at
Dupontwereinvestigating synthetic fibers in order to find a synthetic
alternative to silk. One promisingcandidatewas formed from the reaction
of adipicacid with hexamethylenediamineand wascalled fiber 66 because
each monomer-containingunithad six carbons. It formed astrong, elastic,
largely insolublefiber with a relatively high melting temperature. DuPont
chose this material for production. Suchpolyamidesweregiven the name
"nylons"; thus was born nylon 6,6 .
Poly(vinyl chloride). WhilePVC wasinitially formed by German chemist
Eugen Baumann in 1872, scientistsat B. F. Goodrichdiscovered in 1926
how to make sheets and adhesives from it, starting the "vinylage." PVC's
many applicationsincludewater pipesand joints, buildingmaterials, food
packaging, wireinsulation, and medical components.
Polystyrene. Whilepolystyrenewasprobably first formed by German
apothecary Eduard Simon in 1839, itwasalmost 100 yearslater, in 1930,

10. that the German chemical company I. G. Fraben placed polystyreneon the
market. Polystyrene-moldedpartsbecamecommon place by 1935.
Applicationsof polystyreneincludeloose-fillpackaging "peanuts,"shape-
molded packaging, and disposable utensils.
Poly(vinyl butyral). The polymer poly(vinylbutyral)(PVB)wasfirst used
in automotivesafety glass in 1938 to preventflyingglass resulting
from automobile accidents and continuesto be utilized in the twenty-first
century for this purpose .
Other important synthetic polymers. World War IIhelped shape the
futureof polymers. Wartimedemandsand shortages encouraged scientists
to seek substitutes and materials that exceeded currently available
materials. Duringand after the war new materials were developed, spurred
by needsin the electronics, medical, communications, food, aerospace, and
other industries. The aromatic nylons(armids)Kevlar (capable of stopping
a speedingbullet and used as tire cord) and Nomex(used in constructing
fire-resistant garments) weredeveloped. Polycarbonatessold under the
trade namesof Merlon and Lexon weredeveloped that substituted for glass
in many automotiveproductssuchas tail lights. Other key developments
included polytetrafluoroethylene, aslick material also known as Teflon;
polysiloxanes, also know as silicones, which have an extremely wide
temperature-userangeand were a componentof the soles of the shoes that
first touched the moon; and polyester fibers and plastics such as
poly(ethyleneterephthalate) (PET), used in carbonated drink bottles .

11. .
Even with this early commercialactivity, little was actually known about
polymers. German chemistHerman Staudinger studied the polymerization
of isoprene(a five-carbon hydrocarbon containinga doublebond that is
obtained as a productof the degradation of naturalrubber by heating) as
early as 1910. Intrigued by the differencebetween this synthetic material
and naturalrubber he began to study giant molecules. Many of his fellow
scientists told him there wasno such thing as giant moleculesand that he
was wasting his time. By 1920 hepublished a summary of his studiesand
correctly proposed linear structuresfor polystyreneand
polyoxymethylene. X-ray studieswereused to supportthe concept of
macromolecules.
From his studiesCarothers established several concepts. First, polymers
could be formed by employingalready known organicreactionsbut with
reactants that had morethan one reactive group per molecule. Second, the
forces that bring together the individualpolymer unitsarethe same as
those that hold together the starting materials: namely, primary covalent
bonds. Muchof the polymer chemistry namesand ideas that permeate
polymer science werestandardized throughhis efforts.
Types of Synthetic Polymers
Elastomers. Elastomersare polymerspossessingchemical and/or physical
crosslinks .These crosslinks allow the stretched, deformed segmentsto
return to their original locations after the force is removed. The "use"
temperaturemustbe above the T g to allow ready chain slippage as the
rubbery material is flexed and extended. The forces between the chains
should be minimalto allow easy movementof these chain segments.

12. Finally, the chains mustbe presentin an amorphous, disorganized fashion.
As force is applied and the material distorts or elongates, the randomly
oriented chains are forced to align and take moreordered positionswith
the chains, formingcrystalline regionsthat resist ready movement. Asthe
force is removed the material has a tendency to return to its original
disorganized state and therefore its pre-stretched shape. The formation of
the crystalline regionsas the material is stretched gives the material a
greater tensile strength(i.e. an increased forceis necessary for further
elongation) at high extensions. Crosslinked vinylpolymersareideal
materials to be used in elastomers: the attractive forcesbetween chains is
low and their T g is below room temperature.
Thermosets and thermoplastics. Thermosets are materials that have
sufficient crosslinking present so that they are prevented from being
soluble and melting when heated. Such materials are therefore difficult to
recycle. Thermoplastics are materials that melt on heating and generally
contain little or no crosslinking. They can be recycled more easily through
heating and reforming. Linear polymers are thermoplastic materials.
Plastics.Plastics requirepropertiesthat are intermediatebetween
elastomers and fibers. Engineeringplastics can be readily machined, cut,
and drilled. Condensation polymersaretypically engineeringplastics while
vinylpolymersaretypically plastics. Table 4 contains a listing of the most
common engineeringplastics and plastic materials and Table 5 the volume
of engineeringplastics and plastics produced in the United States.
Coatings.Coatings and adhesives are generally derived from polymersthat
are considered to be plastics, although there are major groupsthat do not.
For instance, silicone rubbersare elastomers that can be used as adhesives.
Coatings, or coverings, are generally highly viscous(low flowing)materials.
Coatings protect surfacesfrom the degradativeeffects of oils, oxidative
chemical agents, extreme temperatures, rain, snow, and ionizingradiation.
Coatings mustadhere to the surfacethey are applied to. Coatings are
typically a mixtureof a liquid (vehicle or binder/adhesive)and oneor more
colorants (pigments). Coatings often also contain a number of so-called
additivesthat can furnishadded protection against ionizingradiation,
increase the rate of dryingand/or curing(crosslinking), and prevent
microorganism growth. Coatings are specially formulated for specific
purposesand locationsand can be divided into fivegroups:
Oil paintsconsist of a suspension of pigment(colorant) in a dryingoil such
as linseed oil.

13. Oil varnishesconsist of a polymer, either naturalor synthetic, dissolved in a
dryingoil together with the necessary additives such as catalyst that
promotescrosslinkingof the dryingoil.
Enamelsare oil varnishes with pigment added.
Lacquers are polymer solutionsto which pigments have been added.
Latex paintsare polymer latexes, often poly(methylmethacrylate) and
polyacrylonitrile, to which pigments have been added. They accountfor
well over one half of the commercial paint used.
Hardeningor dryingconsists of removalof solvent (evaporation)and/or
crosslinkingof a dryingoil that contains C=C units.
Adhesives. In contrast to coatings that mustadhere to only one surface,
adhesives are used to join two surfacestogether (Table 6). Adhesion for
both adhesives and coatings can occur through a number of mechanisms
includingphysicalinterlocking, chemical adhesion where primary bonding
occurs between the adhesive and the surfacesbeing joined, secondary
bondingwhere hydrogen bondingor polar bondingoccurs, and viscosity
adhesion wheremovementis restricted because of the viscousnature of
the adhesive material. Adhesivescan be divided accordingto the typeof
delivery of the adhesive or by the typeof polymer:
Pressure-sensitiveadhesives like those used on Post-It-Notes often contain
the same adhesivematerial used in more permanentadhesiveslike Scotch
Tape except in lesser amounts.
Reactive adhesives are short chained polymersor monomersthat solidify
through polymerization or crosslinkingafter application.
Plywood isformed from the impregnation of thin sheets of wood with resin
that dries after the sheets are pressed together. Phenolic thermosets such
as those developed by Bakelite are often used as the resinsfor plywood.
Adhesivesmade from cyanoacrylatesare amongthe best known adhesives,
sold under tradenames such as Super Glueand Crazy Glue. Monomerssuch
as butyl-alpha-cyanoacrylate(Figure 16)polymerizespontaneously in the
presenceof moisture. The presenceof the cyano and acrylate groups, both
quite polar, makes this a particularly good adhesive; it is used in surgery
and for mechanical assemblies.
Laminates. The combination of an adhesive and an adherentis a laminate,
a type of composite. Commerciallaminates are produced on alarge scale
with wood as the adherent and phenolic, urea, epoxy, resorcinol, or
polyester resins as the adhesive. Plywood is an example of a laminate.
Laminates of paper or textile includeFormicaand Micarta. Laminates of
phenolic, nylon, or silicone resinswith cotton, asbestos, paper, or glass

14. textiles are used as mechanical, electrical, and general purposestructural
materials.
Conductive polymers.Most polymersarenonconductiveand polymers
such as polyethylene, polypropyleneand polytetrafluoroethylene(Teflon)
are used as insulators. Even so, somepolymershave been found to conduct
electricity. An exampleis polyacetylene; oxidation with chlorine, bromine,
or iodinevapor makespolyacetylenefilm 10 9 (1,000,000,000)timesmore
conductivethan the non-treated film .This treatment with a halogen is
called "doping."Other polymersincludingpolyaniline, polythiophene, and
polypyrrolehavebeen found to be conductingafter dopingand these
materials are now being used in a variety of applications.Doped
polyanilineis employed asa conductor and as an electromagnetic shielding
for electronic circuits. Polythiophenederivativesare used in field-effect
transistors. Polypyrroleisused in microwave-absorbing"stealth" screen
coatings and in sensing devices. Poly(phenylenevinylidene)derivativesare
used in the production of electroluminescentdisplays.
.
.
Polymer Synthesis
The process by which polymersare formed from monomersiscalled
polymerization. Polymerization occursby oneof two basic reactions:
addition or condensation. In addition polymerization, entiremonomersare
linked together to form longchains. In condensation polymerization, some
small molecules(such as water) are released as polymer isformed.
Polymerization reactionsmay be divided into two major categories:
stepwise processesand chain-type processes. In the step-wise process,
reactants are brought together and heated. Initially short chains are formed
and only at the end of the reaction are long chains formed. Reactions
generally require hoursto form the polymers. It is by this process that
condensation polymersaregenerally made.
Vinylpolymersare formed using a chain-type processthat involvesthree
steps:
Initiation. This first step requiresthat the monomer'sdoublebond is
broken. This can occur by meansof heat or light, or by the addition of other
chemical compoundsthathave less stable bonds. The decomposition
productsof these chemical compoundsadd to the vinylmonomer, causing

15. the doublebond to break. These materials are called initiators because they
start the polymerization process.
Propagation. This second step involvesgrowthof the polymer chain by the
addition of monomer units. This occursrapidly, within fractionsof a
second.
Termination. Finally, the growth of the chain is stopped (terminated).
The processof initiation, growth, and termination continuesuntil the
monomer is consumed. Reactionsoften occur at or below room
temperature.
Bibliography
Carraher, Charles E., Jr. (2003). GiantMolecules: Essential Materials for
Everyday Livingand Problem Solving , 2nd edition. Hoboken, NJ: Wiley.
Carraher, Charles E. Jr. (2003). Polymer Chemistry. New York: Dekken.
Craver, ClaraD., and Carraher, Charles E., Jr. (2000). Applied Polymer
Science: 21stCentury. New York: Elsevier.
Morawetz, Herbert(1995). Polymers: TheOrigins and Growthof a
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Salamone, JosephC., ed. (1999). ConcisePolymericMaterials
Encyclopedia.M BocaRaton, FL: CRC Press.
Read more: http://www.chemistryexplained.com/Pl-Pr/Polymers-
Synthetic.html#ixzz55ZoiznLL