Polymers

CHAPTER 15: POLYMERS IMPORTANT POINTS TO REMEMBER

1. Polymer: A polymer polymer is a large but single chain-like molecule in which the repeating units are derived from small molecules called monomer, are covalent linked. They have high molecular weight. 2. Polymerization: t is a process in which large number of small molecules called monomer combine together to form polymer under specific conditions of temperature, pressure and catalyst, e.g., polyethylene is obtained obtained from its monomer ethylene ethylene as a result, of polymerisation. polymerisation. n !"2 #!"2 $ %-!"2-!"2-&n 'thylene (olyethylene ). Copolymer: The polymers in which repeating units are derived from two types of monomers are called copolymers. *. Homopolymer: The polymers in which repeating units are derived from same type of monomers are called homopolymers .eg: n !"2 #!"2 $ %-!"2-!"2-&n 'thylene (olyethylene +. Biopolymer: any biomolecules like carbohydrates, proteins are also polymers. They are called biopolymers. . Nat!ral polymer: Those polymers, which are obtained from natural sources are called natural polymers e.g., starch, cellulose, glycogen, proteins, nucleic acid and natural rubber, tarch is polymer of glucose. /atural rubber is polymer of isoprene %2-methyl-l, )-butadiene&. 0. Synt"eti# polymer: They are man-made polymers. ost of them are long chain organic molecules containing thousands of monomer units, e.g., polyethylene, polystyrene, polyvinyl chloride %(!&, bakelite, nylon and acron. 3. Linear polymer: 4inear polymers are well-packed and thus have high densities, high tensile strength and high melting points, e.g., high density polyethene. 5. Bran#"e$ #"ain polymer: (olymers are irregularly packed and thus have low tensile strength and melting points than linear polymers, e.g., low density polythene. 16. Cro%lin&e$ polymer: n these polymers, monomers are cross-linked and formaldehyde network. They are hard and rigid, e.g., bakelite.

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11. A$$ition polymer: The polymers, which are formed by, repeated addition of monomers to the polymer chain. The monomers are unsaturated compounds and commonly derivates of ethene. The addition polymers have same empirical formula as their monomers. n !"2 #!"2 $ %-!"2-!"2-&n 'thylene (olyethylene Con$enation polymer polymer: (o 12. Con$enation (ollymer ymerss form formed ed by the the cond conden ensa satition on of two two or more more than than two two monomers with the elimination of simple molecules like water, /" ), "!l are called condensation polymer. 'g : /ylon 7, is obtained by the condensation he8amethylenediamine and adipic acid with the loss of water molecules. n /"2-%!"2&-/"2 9 n "! -;!"2&*-!" $ < -/"-%!"2&-/"-!-%!"2&*-!-=n 9 n "2 he8amethylenediamine Adipic acid /ylon 7, 1). C"ain 'ro(t" polymeriation : !hain growth polymerisation involves a chain reaction in which successive addition of monomer units takes place .t re>uires an initiator such as a free radical, a carbocation or a carbanion. 1*. Elatomer : A polymer in which these are weak inter-molecular inter-molecular forces forces between long chains. 1+.)!l#aniation: ?hen natural rubber is heated with )-+@ sulphur, it becomes non-sticky elastic. This process is called vulcaniation. 1. T"ermoplati#: These are the polymers, which can be easily softened repeatedly when heated invaded when cooled with little change in their properties. The intermolecular forces in these polymers are intermediate between between those of elastomers and fibres. ?hen heated they melt and form a fluid which can be moulded in to any desired shapes and then cooled to get the desired shape eg :(olythene, polystyrene, polyvinyl chloride, teflon etc. 10. T"ermoettin' polymer: These are the polymers, which undergo permanent change on heating. They become hard and infusible on heating. ?hen heated they get highly cross-linked to infusible and insoluble products. The cross links do not allow them to move freely. e.g., melamine !, bakelite etc.







15. *ormal$e"y$e rein: Those are the polymers made up of formaldehyde and compounds like phenol, urea, melamine, etc. 26. Ba&elite: t is cross-linked condensation polymer of phenol and formaldehyde. t is a thermosetting plastic. t is used for making electrical switches and switch-boards. 21. B!na%S: ynthetic rubber obtained by co-polymeriation of butadiene and styrene. t is used for automobile tyres. 22. +lyptal: t is the condensation polymer of phthalic acid and ethylene glycol. 2). +!tta%per#"a: t is a material very similar to natural rubber. t is a polymer of trans-isoprene. t can also be called as trans-polyisoprene. 2*. Neoprene: t is a polymer of chloroprene%ie: 2-chloro-l,)-butadiene&. 2-chloro-l,)-butadiene&. t is a synthetic s ynthetic rubber. t does not catch fire, therefore, it is used for making conveyor belts in coal mines. 2+. Nylon%,: t is a polymer of caprolactum. t is used for moulding frictionless bearings, gears etc. which work efficiently without lubrication. 2. Nylon%,,: t is condensation polymer of adipic acid and he8amethylene diamine. diamine. t is a polyamide fibre. t is used for making te8tile fibres used in making socks, dresses, sarees, undergarments, undergarments, carpets, etc. 20. Te-lon: t is addition polymer of tetrafluoroethene. tetrafluoroethene. t is a heat resistant plastic. t is used for making body of refrigerators and non-stick kitchenwares. 23. Terylene: t is condensation polymer of terephthalic acid and glycol. t is polyester. t is used for making te8tiles. t is also called dacron. 25. T"io&ol: ynthetic rubber obtained by condensation of ethylene dichloride and sodium poly-sulphide. t is inflammable inflammable and used as rocket fuel. )6. .rea -ormal$e"y$e rein: t is a condensation polymer of urea and formaldehyde. tis used for making unbreakable crockery. crockery. )1. Melamine -ormal$e"y$e rein: t is a condensation polymer of melamine and formaldehyde. t is used for making crockery. )2. Hi'" $enity polyt"ene: t is produced by polymeriation of ethene in presence of Ciegler /atta







//0 .e o- ome #ommer#ially #ommer#ially important polymer Name o- polymer

1. (olythene

Monomer

.e

!"2#!"2 %ethene&

'lectrical insulators, (acking aterials. 2. (olystyrene !"2# !"-!"+ %styrene& As insulator, ?rapping ?rapping material, for toys. ). (olyvinyl !hloride !"2#!"-!l #!"-!l %i %inyl nyl !hloride& !hloride& n the the manufactur manufacturee of rain coats, coats, hand hand bags. *. (olytetrafluroethylene (olytetrafluroethylene !E2# !E2 As lubricant insulator +. (olymethylmethacrylate (olymethylmethacrylate !"2 # !-!") ubstitute of glass and decorative decorative materials. materials. F !!") . (olyacrylonitrile (olyacrylonitrile !"2 # !"-!/ 0. tyrene butadiene rubber !"2#!"- !"#!"2 %GH or Guna - & and !"2#!"-!"+ 3. /itrile rubber%Guna-/& !"2#!"-!"#!"2 and !"2 # !"-!/ 5. /eoprene !"2#!-!"#!"2 F !l 16. (olyethyl acrylate !"2#!"-!!2"+ 11. Terylene Terylene %acron& "!-! "+- !" I "-!" 2-!"2-6" 12. /ylon -  "!-%!"2&*-!" I /"2-%!"2&-/"2

Some important !etion

n making synthetic fibres and synthetic wool. n making automobile tyres and footwear. footwear. aking oil seals, tank linings. As insulator making conveyor belts.

n making films house pipes. Eor making fibres, safety belts. n making brushes, synthetic fibres.







Ans: Giopolymer is the natural polymer that contain many different monomer units, which is essential for life. '8: (olysaccharides or proteins or nucleic acids.

60 2"at $oe PMMA repreent3 repreent3 +i4e it one !e0

Ans: (olymethyl methacrylate. methacrylate. t is used in the manufacture of light shades, sign boards. /0 Arran'e t"e -ollo(in' in t"e in#reain' or$er o- t"eir intermole#!lar -or#e

/ylon- , Guna-, (olythene. (olythene. Ans: Guna-  %elastomer& , (olythene%Thermoplastic& and /ylon-  % fibre&. 70 Ho( i PAN 8Poly A#rylo Nitrile9 prepare$3

Ans: n%!"2#!"-!/& $ %-!"2-!"-&n F

!/ 50 Name t"e r!er ("i#" !le '!m #ontain0

Ans: tyrene - buta diene rubber. ,0 Ho( rayon $i--er -rom il&3

Ans: Hayon is polymer of glucose, where as silk is a polymer of proteins. ;0 2"i#" polymer i in4ol4e$ in t"e man!-a#t!re o- re#or$in' tape3

Ans: Terylene <0 2"at i PCT*E3

Ans: (olymono !hloro Trifluro Trifluro 'thene. =0 2rite t"e monomer !nit o- a&elite0

Ans: (henol and Eormaldehyde 1>0 2"at are Polyami$e3

Ans: The polymer in which amide linkage is present in the chain is called polyamide. 110 110 Eplain t"e $i--eren#e et(een B!na%N an$ B!na%S0

Ans: Guna-/ is a copolymer of 1, )-butadiene and acrylonitrile and Guna- is a co-polymer of 1, )-butadiene and styrene.







Ans: (olyethylene and Teflon

170 +i4e t(o eample o- tep 'ro(t" polymer0

Ans: /ylon- and Gakelite 150 2rite t"e name an$ tr!#t!re o- one o- t"e #ommon initiator !e$ in -ree ra$i#al a$$ition polymerization0

Ans: Genoyl pero8ide 7 ! "+-!---!-!"+ 1,0 2"i#" polymer i !e$ -or ma&in' a non%ti#& #oatin' on pan 3

Ans: Teflon 1;0 Ho( $oe t"e iopolymer $e'ra$e3

Ans: Gy enymatic hydrolysis and also by o8idation 1<0 2"y io$e'ra$ale ynt"eti# polymer "a4e een $e4elope$3

Ans: Eor solution of disposal problem of polymer waste 1=0 2"at i t"e ma@or importan#e o- PHB) polymer3

Ans: t is a biodegradable polymer which easily undergoes bacterial degradation in atmosphere. 6>0 2"at i No4ola#3

Ans: t is a linear polymer of ortho and para hydro8y methyl phenol. Short Answer Type Questions: 2 Marks 2 Marks Each









Ans: Elatomer: They They have have weake weakest st inter inter molecu molecular lar forces forces of attrac attractio tion. n. '8: /atur /atural al rubber rubber,, ulcanised rubber. *ire: They are polymers having stronger forces having hydrogen bonds. They have tensile strength. 'g: nylon, terylene.

T"ermoplati#: They can be easily moulded into desired shape by heating and

then cooling. The force of attraction is intermediate between elastomers and fibres. '8: polythene, polypropene. T"ermoettin' plati#: They have ma8imum force of attraction because they are cross -linked. They do not become soft on heating. '8: Gakelite. 60 State t"e i'ni-i#an#e o- n!mer in t"e polymer name nylon %, an$ nylon %,,0

Ans: /ylon-  means its monomer contains  7 carbon atoms %called caprolactum&. /ylon -  is so called because because both the monomers monomers contain  - carbon atoms atoms each. /0 Ho( i Nylon % ,, i ynt"eize$3

Ans: n /"2-%!"2&-/"2 9 n "! -;!"2&*-!" $ < -/"-%!"2&-/"-!-%!"2&*-!-=n 9 n "2 he8amethylenediamine Adipic acid /ylon 7, /ylon -  is prepared by condensation condensation of adipic acid acid and he8amethylenediamine. he8amethylenediamine. 70 2"at i B!na% S3 Ho( it i prepare$3







,0 2"at are linear linear polymer polymer an$ ran#"e ran#"e$ $ #"ain #"ain polymer polymer0 0 Ho( $o t"e t"ee e $i--er $i--er -rom -rom #ro%l #ro%lin& in&e$ e$ polymer3

Ans: 4inear polymers are well packed and have high densities, high tensile strength and also have a high melting point. '8: "igh-density polythene. Granched chain polymers are irregularly packed and have lower tensile strength and lower melting point than linear polymers. '8: low density polythene. These are different from cross-linked polymers in the sense that the cross-linked polymers are hard, rigid and brittle. '8: Gakelite.

;0 2rite t"e $i--eren#e et(een polya#rylate an$ polyeter0

Ans: (olyacrvlates: %a&These are addition polymers %b&Terylene %b&Terylene is synthesied by the condensation of ethylene glycol and terephthalic acid.

(olyesters %a& these are condensation polymers %b& these are synthesied from various types of acrylic monomers.

<0 2rite t"e e!ation o- preparation o- Terylene0 Terylene0

Ans: n "!- ! "+-!" 9 n %"-!" 2-!"2-6"& $ %-!- !"+-!--!"2-!"2--&n Terephthal Terephthalic ic acid 'thylene glycol Tereylene Tereylene or acron =0 i--erentiate et(een #"ain 'ro(t" an$ tep 'ro(t" polymerization0

Ans: C"ain 'ro(t" polymerization

Step 'ro(t" polymerization







110 2"y i #ationi# polymerization pre-erre$ in #ae o- 4inyli# monomer #ontainin' ele#tron $onatin' al&yl 'ro!p3

Ans: n case of vinylic monomers containing electron donating groups, electron density on double bonded carbon will be more and it can be easily attacked by " 9. o as to undergo cationic polymeriation cations cations are established by electron electron donating alkyl alkyl groups. 160 Ho( $oe t"e preen#e o- CCl7 in-l!en#e t"e #o!re o- 4inyl -ree ra$i#al polymerization3

Ans: !!l*is called chain transfer agents. n the presence of !!*, tyrene polymeries to form polystyrene of a lower average average molecular molecular mass which also contain contain chlorine. The The growing polystyrene radical which normally would add on a monomer reacts with the chain transfer agent to end the original chain and produces a new radical.

1/0 2"y $oe tyrene !n$er'o anioni# polymerization eaily3

Ans: !"+ group is electron withdrawing group. 170 2"at i PHB)3 2"at i it !e3

Ans: ("G stands for (oly-J-hydro8ybutyrate -co- J -hydro8y valerate. Ksed as orthopedic devices and in controlled drug release. 150 Elaorate t"e tr!#t!re o- nat!ral r!er0

Ans: /atural rubber is a linear 1,* polymer of isoprene. n natural rubber the original double bonds







Ans: Gakelite is a condensation polymer and is obtained from phenol and formaldehyde in the presence of basic catalyst. 1<0 Ho( $oe t"e pre preen#e en#e o- enzo!inon enzo!inonee in-l!en#e in-l!en#e t"e -re -ree e ra$i#al polymerizati polymerization on o- a 4inyl $eri4ati4e3

Ans: Geno>uinone traps the radical intermediate to form a non-reactive radical, which is highly stabilied by resonance. o the progress of the chain reaction is interrupted and the reaction stops. Short Answer Type Type Questions: / Marks each 10 Brie-ly $e#rie t"e -ollo(in' term 'i4in' one eample o- ea#"0

(i) Polyole-in (ii) Polyami$e (iii) Polyeter0

Ans (i) (oly olefins. They are addition polymers obtained from unsaturated hydrocarbons containing carbon-carbon double bonds. Eor e8ample, polythene, polypropylene, polystyrene %styrene&. (ii) (oly amides. They are condensation polymers having amide linkage in their molecules. Eor e8ample, nylon-, nylon- %perlon& and nylon-, 16 (iii) (olyesters. They are condensation polymers obtained by the reaction of diacids and dialcohols. The most industrially important polyester, made from reaction of terephthalic acid with ethylene glycol, 600 i--erentiate et(een #"ain 'ro(t" an$ tep 'ro(t" polymerization0 +i4e t"e tr!#t!r!ral -orm!la o- one polymer o- ea#" type0

Ans: Chain growth polymerization polymerization %a& !oncentration of monomers decreases steadily through out the reaction.







/0 2"at i t"e $i--eren#e et(een t"ermoplati# polymer an$ t"ermoettin' polymer3

Ans: Thermo plastic polymers: often and melt on heating, can be remoulded, reset and reshapedL are brittle and are soluble in some organic solvents. Ksually formed by addition polymeriation. Ksually have linear structures. Thermosetting Thermosetting polymers

o not soften on heating but burn if heated for a longer time. !annot be remoulded or reshaped Are more brittle and are insoluble in organic solvents because of three dimensional cross-linking. Eormed by condensation polymeriation. "ave three dimensional cross-linked structures.

70 2"y $oe tyrene !n$er'o anioni# polymerization3 Eplain rie-ly3

Ans: tyrene undergoes anionic polymeriation easily because !"+ group in styrene is electron withdrawing. t involves following steps: a& !hain initiation step: M 9 /"2- 9 !"2# !" $ "2/-!"2-!"M 9 F

!"+ tyrene

F

!"+









50 2"y i #ationi# polymerization pre-erre$ in #ae o- 4inyli# monomer #ontainin' ele#tron $onatin' 'ro!p3

Ans: The cationic polymeriation is preferred in case ofvinylic monomers containing electron donating groups because cationic polymeriation is facilitated. Thus isobutylene undergoes cationic polymerisation easily as it has two electron releasing - !") groups that will stabilie the intermediate cation. ,0 Ho( are polymer #lai-ie$ on t"e ai o- t"eir met"o$ o- ynt"ei3 +i4e t(o eample o- ea#" #la0

Ans: Gased on the modes of synthesis, polymers have been classified into two groups: (i) Addition polymers are those which are obtained by chain growth polymeriation of monomer%s&, containing one or more double bonds. olecular mass of addition polymer is e8act multiple of its monomer%s&. '8amples: (olythene %('&, polypropylene %((&, (olyvinylchloride %(!&, (olystyrene %(&, polyvinyl acetate %(A %(A& etc. !ondensation on polymers polymers are those which are obtained obtained by step grow polymeriati polymeriation on of monomers (ii) !ondensati containing at least two functional groups each.







(c) A$$ition o- !lp"!r to nat!ral r!er impro4e it propertie0 (d) Rayon i !perior to #otton -or !e a an$a'e 8'a!'e90

Ans: (a) ipole-dipole interaction interaction in (! is absent in ('. (b) (olypropene is harder and stronger than (olyethene. (c) ulphur develops cross-linking. (d) trong "-bonding between molecules. =0 2"at $o yo! mean y PI3 2"at $oe it tell ! ao!t a polymer3

Ans: ( is poly disparity inde8 defined as the ratio of the weight average and the number average molecular masses. t is a very important parameter of polymers, which is used to identify the disparity in the polymer. /atural /atural polymers have ( e>ual to one because in them the number of monomers in a chain are fi8ed and it does not change. Gut in case of synthetic polymers the ( is greater than unity because the number of monomers does not remain same and are often more than the re>uired amount.







HI+HER ORER THININ+ SILL .ESTIONS 8HOTS9

1. ?hy is bakelite hard and has high melting pointN 2. Arrange the following alkenes towards order of increasing reactivity in cationic polymerisation : !"2#!"-!"), !")-!"-!l, !"2#!"-!"+, !"2#!"-!!") ). Arrange the following alkenes in order of increasing reactivity towards anionic polymerisation : !"2#!"-!"), !"2#!E2, !"2##!"-!/, !"2#!"-!"+ *.?hat is the monomer of natural rubberN /ame the polymer of trans-isoprene. +. ?hat is the value of ( %polydispersity inde8& for natural polymersN . /ame the copolymer of glycein and aminocaproic acid. 0. Bive two e8amples of biodegradable polymers. 3. ?hat is plastisier N 5. ?hat are pendant groupsN 16.?hat are monomers of Blyptal N 11.?hich 11.?hich polymer is used for non-stick kitchen waresN

Polymers

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