mw polymers ppt b5

7/25/2019 Mw Polymers Ppt b5

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Polymers!:

Chapter 7 Principals of Polymeric Materials= Polymer science basic overview, chemicalmakeup, strenthenin techniues an" fillers,

morpholoy, visco#elasticity, etc$$$ Chapter % Polymer families

Chapter & Manufacturin techniues

Chapter '( )election of Plastic Materials =Puttin it all toether # *ow to select polymers+ef C-), Curbll, .upont, etc/0


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1ur 2ocus:

Polymer selection

Commo"ity plastics:

Polyethylene # 3($%( 4lb Polystyrene # 3($75 4lb

-nineere" plastics

Polyami"e +6ylon0 # 3'$5( 4lb Peek # 35 4lb


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http:44www$americanplasticscouncil$or4s8apc4in"e9$asp

Plastic: 1ranic material with repeatin molecular units that can be

forme" into usable soli" shapes by castin, sinterin or melt processin:

Chapter : Principles of Polymeric Materials:

http:44www$americanplasticscouncil$or4s8apc4sec$asp;.=?C>.=@'(?.>.=&A(

Boo" *istory:


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http:44www$americanplasticscouncil$or4s8apc4in"e9$asp


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P +ref$ Chapter 7$'0

>$ Molecular eiht

>>$ PolymeriDation eactions


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Easic Molecular )tructure:

Polyethylene = manymolecules of ethylene

-thylene moleculesattach to each otherthrouh covalentbon" betweencarbon atoms+nee"e" to satisfyvalence reuirements

for carbon0

Many of these ethylenemolecules Foin toetherpro"ucin polyethylene

)ee physical structure


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Easic Molecular )tructure:

Polyethylene Molecule:

* = *y"roen


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Molecular eiht


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Molecular eiht -K P1>6;):

Ln"erstan" what molecular weiht means when"ealin with polymers

Ln"erstan" the effect of molecular weiht onmaterial properties

Ln"erstan" entanlement

I. Molecular Weight


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Molecular eiht


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Molecular eiht

Molecular weiht is the sum of the atomic weihts of the atomsthat make up the molecule$

Carbon has an atomic weiht of 'A$('' rams4mole$ 'A is closeenouh for what weNre "oin

< mole is 6.0221415 1023 atoms or molecules

;his is known as


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Molecular eiht

;o put it into perspective:

< mole of water +' o9yen G'H an" A hy"roen G'H0 weihs'% rams that is barely enouh to cover the bottom of a lass$

< mole of polypropylene +@ carbons G'AH an" hy"roenG'H0 weihs @7%,((( rams +assumin &,((( mers have linke"up0

;hat converts to aroun" %@( poun"sor almost a full aylor"$

Baylor"

I. Molecular Weight


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Molecular eiht

;he atomic weihts of the atoms most commonly foun" inpolymers are:

Hydrogen (H) = 1 g/mole (1.0079)

Carbon (C) = 12 g/mole (12.011)

Nitrogen (N) = 14 g/mole (14.007)

Oxygen (O) = 16 g/mole (1.999)

C!lorine (C") = #. g/mole (#.4#)

I. Molecular Weight


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Molecular eihthen we talk about molecular weiht in terms of polymers, we are really

talkin about the length of the individual chains$

;he polymeriDation process is subFect to variation so there is no sinlechain lenth, there is actually a wi"e rane of lenths, so when we"iscuss molecular weiht, we really mean the averae molecular

weihtof the material$ ;his averae is foun" by measurin samples ofthe material as it is pro"uce"$

I. Molecular Weight


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Molecular eiht

;here are two "ifferent cateories of molecular weiht averaethat are commonly use":

;he first is the 6umber


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Molecular eiht

;he fiure to the riht represents a

typical molecular weiht"istribution$

;he vertical a9is represents

the number of chains at that

lenth$

;he horiDontal a9is represents the

"ifferent chain lenths$

Notice that the longer chains are to the left on the graph and the shorter

chains are to the right.

I. Molecular Weight


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Molecular eiht

;he 6umber


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$ole%&lar 'eig!t

N&mber erage $ole%&lar 'eig!t ( ) *xam+le,

'e !ae,

10 mole- o olyet!ylene (*) t!at are 00 monomer- long

mole- o * t!at are 100 monomer- long

mole- o * t!at are 00 monomer- long

hat is

I. Molecular Weight


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Molecular eiht

6umber


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$ole%&lar 'eig!t

!e 'eig!t erage $ole%&lar'eig!t ( ) tae- into a%%o&ntt!at t!e larger mole%&le- %ontain am&%! !ig!er amo&nt o t!emole%&lar ma-- o t!e +olymer.

!e 'eig!t erage $ole%&lar'eig!t i- almo-t al3ay- !ig!ert!an t!e N&mber erage$ole%&lar 'eig!t ( ).

I. Molecular Weight


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Molecular eiht

ook at the numbers from the previous e9ample:

'( moles of P- that are 5(( monomers lon

5 moles of P- that are '(( monomers lon

5 moles of P- that are %(( monomers lon

Calculate the

I. Molecular Weight


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Molecular eiht

Calculate the

2in" the weiht fractions:

'( 9 5(( 4 &5(( = 5A$R

5 9 '((4 &5(( = 5$@R5 9 %(( 4 &5(( = A$'R

= +($5A 9 5((0 J +($(5@ 9 '((0 J +($A' 9 %((0 = (5$@monomers lon

I. Molecular Weight


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Molecular eiht

Sust knowin the averaes isnot enouh, the "istributionof the molecular weihtsalso has a lare effect onhow the material willprocess an" its properties$

< broa"er or Twi"e specN"istribution may make thematerial unsuitable for

processes like inFectionmol"in, but better suite"for processes like e9trusion,blow#mol"in, orthermoformin$

I. Molecular Weight


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Molecular eiht

2or inFection mol"in ra"esof material, a narrower"istribution is better$

hen the "istribution is

narrow, the polymerchains will melt an" flow ataroun" the sametemperature$

;he loner the chains, thehiher the viscosity orresistance to flow$

I. Molecular Weight


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Molecular eiht

hen you have a broa" or even a bi#mo"al "istribution, the shorter chainsmelt more uickly an" allow someflow, while the loner chains hol" thematerial toether$

;his ives the polymer mi9ture meltstrenth which allows it to be use" forsome of the other processesmentione" other than inFection

mol"in$

I. Molecular Weight


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Molecular eiht

Kou can have virtually aninfinite number or"istributions with the samenumber averae molecularweiht$


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Properties

hen makin polymers, the oal is to make a material with thei"eal properties$

;he loner the molecules +or the hiher the molecular weiht0

the hiher the entanlement forces:

oner hair is har"er to et untanle" than shorter hair

I. Molecular Weight


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Properties

Increasing the molecular weight of the materialincreases many of the properties of the material byincreasing the entanglement of the molecules.

A higher molecular weight:

Increases the chemical resistance - to a point

It takes more damage to the main chains of themolecules before it will aect the strength of thematerial

he big loophole to this is if you ha!e a chemical

that is !ery similar to the chemical makeup of the

main chain" it will dissol!e it much more easily

#$ike %issol!es $ike

I. Molecular Weight


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Properties

< hiher molecular weiht:

>ncreases how far the material can stretch before rupturin+"uctility0

;he hiher "eree of entanlement allows the material to

be pulle" further before the chains break

I. Molecular Weight


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Properties


>ncreases "uctility: < can"le an" Polyethylene +P-0 havebasically the same molecular structure$ ;he chain lenth ofthe can"le is Fust much shorter than that of the P-$ >f you

ben" a bar of P- in half it will ben", if you ben" a can"le inhalf, it will fracture$

I. Molecular Weight


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Properties


>ncreases the impact resistance of the material

;he hiher "eree of entanlement means that in or"er torupture, more polymer bon"s nee" to be broken, this means

that the polymer can absorb more enery before failin$

I. Molecular Weight


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Properties


>ncreases the weather resistance of the material )ame type of reasonin behin" the increase in chemical

resistance, the chains are loner, so they can withstan" more"amae before the mechanical properties will start to

"iminish

I. Molecular Weight


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Properties


>ncreases the viscosity of the material makes it har"er toprocess the material usin conventional metho"s

;he loner the chains, the har"er it is to et them to flow

UMore tanle"

I. Molecular Weight


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ro+ertie-

ro%e--or- 3ant material- t!at 3ill lo3 ea-ily in order to orm %om+lexgeometrie- b&t t!at %an ae%t t!e +ro+ertie- o material &-ed to %reate t!e+rod&%t.

$any time- it t&rn- o&t to be a trade5o bet3een t!e re&ired +ro+ertie- and

+ro%e--ability o t!e material.

C8- and 8- are made rom t!e -ame material a- mo-t -aety gla--e-oly%arbonate.

:aety gla--e- re&ire a !ig!er mole%&lar 3eig!t in order to +roide t!ene%e--ary +ro+erty o im+a%t re-i-tan%e.

C8- and 8- re&ire a lo3er mole%&lar 3eig!t material in order to ill o&tt!e t!in 3all-. C8- and 8- %an -!atter -aety gla--e- don8t.

I. Molecular Weight


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Properties

I. Molecular Weight


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Molecular eihtVuestions


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>>$ PolymeriDation Processes:


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ter reie3ing t!e olymeri;ation +re-entation-t&dent- -!o&ld,

< e able to name and de-%ribe t!e t3o ba-i% met!od- o +olymeri;ation

o t!ermo+la-ti% material-

< >nder-tand t!e dieren%e bet3een a !omo+olymer %o+olymer alloy

and blend

< >nder-tand !o3 bran%!ing %an ae%t t!e +ro+ertie- o t!e material

-K P1>6;):II. Polymerization


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1verview

;hermoplastic molecules are lon stran"s or chains of atoms$

)maller atoms or roups of atoms +mers0 are linke" toether toform the lon chains so that they are many units lon$

+many TmersN polymer0

;his lon lenth to "iameter or hih aspect ratio ives polymericmaterials very "istinctive properties like hih strenth withvery liht weiht$

;he reason for these properties is that the polymer chains are

hel" toether "ue to -6;


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1verview

-ntanlement isnNt the only thin that hol"s the moleculestoether, there are chares on the molecules that attract theother molecules +polar forces0, an" weak attractive forcesbetween the molecules +secon"ary forces sometimes calle"

Wan "er aalNs forces$0

;he two main polymeriDation metho"s or reactions use" to createpolymer chains are:

;>16 an" C16.-6)16

-16)

II. Polymerization

II P l i ti


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ddition ?ea%tion-

@n addition rea%tion- t!e do&ble or tri+le bond- bet3een t!e atom- o t!e mole%&le are broenand t!e %!ain gro3- longer 3!en anot!er mole%&le t!at !a- al-o !ad it- bond- broen

lin- toget!er 3it! it.

@n olyet!ylene t!e do&ble %arbon bond in t!e et!ylene mole%&le -e+arate- and lin- 3it!

anot!er %arbon bond rom anot!er et!ylene mole%&le.

II. Polymerization


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Conden-ation ?ea%tion-

@n %onden-ation rea%tion- a +ortion o t!e Amer8 mole%&le rea%t- 3it! anot!erAmer8 mole%&le to orm a ne3 bond and gie- o 3ater %arbon dioxide or

+o--ibly an a%id.

!e +ortion o t!e Amer8 t!at rea%t- i- no3n a- t!e &n%tional gro&+.

Conden-ation rea%tion- &-&ally tae longer t!an addition rea%tion-

< @n addition rea%tion- any %!ain end 3ill rea%t 3it! any ot!er %!ain end and

t!e mole%&le- gro3 at dierent rate- de+ending on 3!at -i;e %!ain-

%ombine.< @n %onden-ation rea%tion- t!e %!ain- ty+i%ally gro3 at t!e -ame rate a- t!e

%!emi%al- t!at mae &+ t!e +olymer %!ain are %on-&med t!e rea%tion rate

-lo3- do3n.

II. Polymerization

Con"ensation PolymeriDation +-9amples inclu"e: nylons II P l i ti


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Con"ensation polymeriDation

chemical reaction pro"ucesnew polymer!

'$ ;hermoplastic, or

A$ ;hermoset +chemical bon" attachesmolecules toether0 can not be remelte" orrecycle" -9: Most elastomers +natural rubber,butyl, neoprene, silicone, etc$0

Con"ensation PolymeriDation +-9amples inclu"e: nylons,polyesters, urethanes, natural rubber0

II. Polymerization

II Polymerization


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-9ample: Con"ensation eactions

eacts

P-;

II. Polymerization

II Polymerization


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ey Concepts to emember:

enth of polymer chains, n, can becontrolle" with process parameters +heat,pressure, time0 1 catalyst$

enth of polymer has sinificant impact onpolymer properties see previous section$

Many "ifferent polymers can be create"

from the same carbon backbone aspolyethylene inclu"in:

II. Polymerization

II Polymerization


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ey Concepts to emember:

CopolymeriDation polymer chain with two"ifferent monomers increases the breath ofplastics enormously$

;wo types: Elen"s an" alloys mi9in two ormore polymers toether +at least 5R of anotherpolymer reuire"0$ Most XnewY polymers are simply blen"s or alloys!

>f resultant polymer behaves as a new sinle polymer alloy

>f resultant polymer retains some characteristics asoriinal polymers # blen"

II. Polymerization

II Polymerization


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*omopolymer

If each of the circles in the chain was asingle &mer'" this strand would beconsidered a homopolymer because allof the &mers' are the same.

II. Polymerization

II Polymerization


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Copolymers

(ometimes two types of &mers' will be

polymeri)ed together in order tomanipulate the properties of the *nalproduct. hese are called copolymers.(hown is an alternating copolymer inwhich each of the &mers' alternates inan ordered fashion

II. Polymerization

II Polymerization


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Copolymers

+hen one type of &mer' alternates with

no speci*c pattern" the arrangement isknown as a random copolymer.

Alternating and random copolymerswith the same &mers' can ha!e !erydierent properties.

II. Polymerization

II. Polymerization


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Copolymers Braft Copolymer

+hen &sections' of one type of polymer isattached or &grafted' to the main chain ofanother polymer

II. Polymerization

II. Polymerization


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+hen small groups of monomers areattached to each other in alternatingfashion" the product is called a blockcopolymer

Copolymers Elock Copolymer

II. Polymerization

II. Polymerization


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;erpolymer

+hen there are three types of &mers' polymeri)edtogether it is known as a terpolymer.

Acrylonitrile ,utadiene (tyrene A,( is a terpolymerof Acrylic" ,utadiene rubber" and (tyrene.

his gi!es the Acrylic and (tyrene added impactresistance and the properties can be manipulated by

changing the amount of each of the indi!idual &mers'

II. Polymerization


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Eranchin

Side branches off

of the main chain

%uring the polymeri)ation

process" reactions canalso happen o of the sideof the main chain. heseside-chains are known asbranches and the

branches increase theentanglement of thepolymer chains and canalso aect the propertiesof the *nal productdepending on the degree

of branching.

II. Polymerization


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Eranchin

>f there is a lare number of branches,or the branches are very lare, thisserves to hol" the main polymerchains further apart from each other$hen they are hel" further apart, there

is a lower "eree of entanlement inthe polymer which lea"s to a softer,more "uctile material$ ;he a""itionalspace between the molecules makes iteasier for them to flow past one

another$ >n materials ma"e withcon"ensation reactions, there is verylittle if any branchin present$

< stack of tree branches will be muchsmaller if you strip off all of the smaller

branches$

II. Polymerization

II. Polymerization


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PolymeriDation

Vuestions

7 A: ;ypes of Polymers:


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7$A: ;ypes of Polymers:

eview C-) level A materials!!!!


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Main Cateories of Polymers:

Plastics:

;hermoplastics can be remelte": -nineere" ;hermoplastics

Commo"ity ;hermoplastics

;hermosettin Plastics can not be remelte" -nineere" ;hermosets

Commo"ity ;hermosets

-lastomers:

;hermosets an" thermoplastic!!

mw polymers ppt b5

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