Polymer Introduction

8/4/2019 Polymer Introduction

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Course Code : MSE-240 [3-1]

Course Title : Engineering Polymers

Polymers: Chemistry and Physics of Modern

Materials by J. M. G. Cowie and Valeria Arrighi,3rdEdition, CRC Press, 2007.

Assessment : Assignments 5%

Quizzes 15%OHT Exam 30%

Final Exam 50%

Total 100%


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Introduction

Macromolecules


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Materials Classification


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Polymers

Monomer

Covalent bond
http://upload.wikimedia.org/wikipedia/commons/0/03/Single_Polymer_Chains_AFM.jpg


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Basics

Polymers form a large class of engineeringmaterials, which include plastics, rubbersand adhesives

They are large organic molecules, whichhave molecular weights of10,000 to 100,000g/mole

Polymerization is the process used to jointhe small organic molecules into these hugemolecules


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Introduction

Polymers many parts

Polymers

Plastics

Thermoplastics Thermosetting Plastics

Elastomers

Can be

reheated and

formed

into new

materials

Cannot be reformed

by reheating.

Set by chemical reaction.


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Propylenemonomer

PolypropyleneA polymer

Monomer vs. polymer

A monomer is the simple molecule that is covalentlybonded with other monomers to form long molecularchains.A polymer is the long-chain molecule formed frommonomer units.


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Polymers

Polymers can be divided into 2 types :

Naturally occurring polymers

Synthetic polymers


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Natural Polymers

Polymers that exist in plants or animals

Examples of naturally occurring polymers:

Protein : muscles

Carbohydrates : cellulose

Natural rubber : latex


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Natural Polymers


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Natural Polymer
http://upload.wikimedia.org/wikipedia/commons/8/81/ADN_animation.gif


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Cotton fiber is mostly cellulose, and cellulose is

made of chains of the sugar, glucose linked

together a certain way.


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GlucoseStructural formula.

Straight chain

glucose

H-C=O

|

H-C-OH

|

HO-C-H

|

H-C-OH

|

H-C-OH

|

CH2OH

Glucoseglucose bending

GlucoseTwo ring-shape

versions

alpha-glucose

beta-glucose

Glucose bends itself into 4

different shapes millions of times

a second

1

4

6

2

3

5

Used inmaking

cellulose

Used inmaking

starch

flips

eitherwaybends


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Synthetic Polymers

Polymers made in industry from chemical

substances

Scientists are able to copy structures of

natural polymers to produce synthetic

polymers through scientific research


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Synthetic Polymers

Many ofraw materials for synthetic polymersare obtain from

-> Petroleum

Synthetic polymers Plastics

Fibers

Elastomers


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Homopolymer and Copolymers

Homopolymers: Polymer chain is made up of singlerepeating units.

Example: AAAAAAAA

Copolymers: Polymer chains made up of two or more

repeating units. Random copolymers: Different monomers randomly arranged in

chains. e.g.:- ABBABABBAAAAABA

Alternating copolymers: Definite ordered alterations of monomers.e.g.:- ABABABABABAB

Block copolymers: Different monomers arranged in long blocks. Eg:-AAAAA.BBBBBBBB

Graft copolymers: One type of monomer grafted to long chain ofanother. e.g.: AAAAAAAAAAAAAAAAAAA

B

B

B

B

B

B


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Rubber Toughening of PS

High-impact polystyrene, or HIPS for short

Polystyrene is a rather brittle material. But littlepolybutadiene spheres are rubbery, remember, and

they can absorb energy under stress. This keeps the

polystyrene from breaking.


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Tacticity

Polypropylene (PP)
http://upload.wikimedia.org/wikipedia/commons/f/f9/Polypropylen.svg


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Polymers Why?

Polymers as a class of materials are lightweight

and corrosion resistant with relatively low

melting points.

Polymers are relatively inexpensive.

They can be readily formed into a variety of

shapes

Some polymers are transparent, some are good

electrical conductors, some are good electricalinsulators.

Some have low coefficient of friction, e.g. low-

stick cookware.


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Characteristics of Polymers

Polymers can be very

resistant to chemicals.

Consider all the cleaningfluids in your home that

are packaged in plastic.

Many of these chemicalsare very corrosive and

abrasive agents.


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Polymers can be both thermal and electrical

insulators.

Consider all the appliances, cords, electricaloutlets, and general wiring that are made of or

covered with polymeric materials.

Thermal resistance is evident in the kitchen

with pot and pan handles made of polymers.


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Generally, polymers are very light in masswith varying degrees of strength.

Consider the range of applications from a

piggy bank to the frame structure of spacestations,

or from delicate nylon fiber to Kevlar, which is

used in bulletproof vests.


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Applications

Toys,

Home appliances,

Structural and decorative items in the home, Coatings, paints,

Adhesives,

Foams, packaging,

Automobile interiors and exteriors, etc.


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Polymerization

Polymerization is the process used to join the

small organic molecules into these huge

molecules called polymers


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a. AB type

HO COOH

b. AA (A2) and BB (B2) type

HOOC COOH HOCH2CH2OH

c. Three functional group for crosslinked polymers

HOCH2CHCH2OH

OH

Types of Monomer


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Functionality of monomer (f)

Number of covalent bonds that a monomer

molecule or monomeric unit in a

macromolecule or oligomer molecule can

form with other reactants.


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Functionality of monomer (f)

There are no monofunctional monomers. If f = 2, a linear chain macromolecule can be formed.

Iff > 2, a branch point can be formed leading to a

branched macromolecule or a network.

Ethene and ethylene glycol are examples of

difunctional monomers, glycerol is an example of a

trifunctional monomer, and divinylbenzene and

pentaerythritol are examples of tetrafunctionalmonomers.
http://en.wikipedia.org/wiki/File:Ethene_polymerization.pnghttp://upload.wikimedia.org/wikipedia/commons/7/79/Polymer_Branch.svg


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What is the Functionality of the following

monomers in reaction with (i)styrene C6H5-

CH=CH2

and (ii) adipic acid HOOC(CH2)

4COOH

1.

2.

3.

(i) 2

(ii) 0

(i) 0

(ii) 2

(i) 2

(ii) 0


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Elementary Saturated Dicarboxylic

AcidsCommon

nameIUPAC name Chemical formula

Oxalic acid ethanedioic acid HOOC-COOH

Malonic acid propanedioic acid HOOC-(CH2)-COOH

Succinic acid butanedioic acid HOOC-(CH2)

2-COOH

Glutaric acid pentanedioic acid HOOC-(CH2)3-COOH

Adipic acid hexanedioic acid HOOC-(CH2)4-COOH

Pimelic acid heptanedioic acid HOOC-(CH2)5-COOH

Suberic acid octanedioic acid HOOC-(CH2)6-COOH

Azelaic acid nonanedioic acid HOOC-(CH2)7-COOH

Sebacic acid decanedioic acid HOOC-(CH2)8-COOH

undecanedioic acid HOOC-(CH2)9-COOH

dodecanedioic acid HOOC-(CH2)10-COOH


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Elementary Aromatic Dicarboxylic

Acids

Common name IUPAC nameChemical

formula

Phthalic acid

benzene-1,2-

dicarboxylic acid

(o-phthalic acid)

C6H4(COOH)2

Isophthalic acid

benzene-1,3-

dicarboxylic acid

(m-phthalic acid)

C6H4(COOH)2

Terephthalic

acid

benzene-1,4-

dicarboxylic acid

(p-phthalic acid)

C6H4(COOH)2
http://en.wikipedia.org/wiki/File:Terephthalic-acid-2D-skeletal.pnghttp://en.wikipedia.org/wiki/File:Isophthalic-acid-2D-skeletal.pnghttp://en.wikipedia.org/wiki/File:Phthalic-acid-2D-skeletal.png


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Elementary Unsaturated

Dicarboxylic AcidsType Common name Chemical formula

Monounsaturated:

two isomeric

forms:

cis and trans

Maleic acid (cis form)

and Fumaric acid (trans

form)

HO2CCH=CHCO2H


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Vinyl Polymers

Vinyl Monomers, CH2=CH-X


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Vinylidene Polymers

Vinylidene Monomers, CH2=C(X)Y


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Polymerization mechanisms

The synthetic process is Polymerization.

Addition polymers are formed by covalently

joining individual molecules without changing

the chemistry of the reactants.

Condensation polymers are produced when

two or more types of molecules are joined by a

chemical reaction that releases a by-productsuch as water.


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Condensation Polymerization

This method (also known as step-growth)

requires that the monomers possess two or

more kinds of functional groups that are able

to react with each other in such a way that

parts of these groups combine to form a smallmolecule (often H2O) which is eliminated from

the two pieces. The now-empty bonding

positions on the two monomers can then jointogether .


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Different Condensation Linkages


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Condensation Reaction


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Condensation Polymerization

PET


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Polyester is a

copolymer. It is made

from equal amounts

of two different

monomers.

Polyester is used to

make bottles and

fabrics.

P l t i d f th t t hth li id ( t h i
http://en.wikipedia.org/wiki/Image:Lilit.jpg


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H O C

O

Polyester is made from the two monomers, terephthalic acid (note: ph is

silent) and ethylene glycol (car antifreeze). This makes a popular plastic

called PETE, which is short forPolyethylene Terephthalate. The synthesis

is also a dehydration reaction because wateris given off.

Hence the name POLYESTERESTER groups formed

PETE


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PET Animation


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When these two monomers are in the same

beaker, they combine and give off a molecule of

water. This is called a dehydration reactionbecause we are taking away (de) water (hydra).

Hexamethylene diamine

methylene x 6 (hexa) amine x 2 (di)

Tetramethylene

dicarboxylic acid (adipic

acid)


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Back to Condensation


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Aramid and Nylon

Nylon is a generic designation for a family of

synthetic polymers known generically as polyamides.

Aramid is a shortened form of "aromatic polyamide".
http://upload.wikimedia.org/wikipedia/commons/8/8c/PA6-PA66.pnghttp://upload.wikimedia.org/wikipedia/commons/b/bf/Kevlar_chemical_structure.png


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Hydrogen Bonding


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Why does

nylon makesuch good

fibers?Intermolecular

forces like hydrogen

bonding


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Condensation Polymers


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Types of Polymerization


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Ring Opening Polymerization


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Ring Opening Polymerization

Propylene oxide

Poly(propylene oxide)

Nylon 6


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Nylon Naming


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Polyurethane

Polyurethanes are made from a dialcohol and

diisocyanate monomers. The isocyanate

compounds contain the functional group

(O=C=N-). A rearrangement reaction leads tothe formation of the urethane linkage.

Technically polyurethane is not a

condensation polymer since no molecules arelost, but the functional group does rearrange.


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Polyurea and Polyurethane

a polyurethane


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Spandex One unusual polyurethane thermoplastic elastomer is

spandex, which DuPont sells under the trade name Lycra. It

has both urea and urethane linkages in its backbone. What

gives spandex its special properties is the fact that it has hard

and soft blocks in its repeat structure.


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Addition Polymerization

Addition or chain-growth polymerization involves therearrangement ofbonds within the monomer in such

a way that the monomers link up directly with each

other. A chemically active molecule (called an

initiator) is needed to start a chain reaction.


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h l h f h h ( )


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CC

H

H H

H

H

C

H H

C

H

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

High temperature or UV light can cause two of these shared (paired)

electrons to become unshared (unpaired).

These unpaired electrons are eager to pairup with another electron. If this ethylenemolecule bumps another ethylenemolecule, the unpaired electrons will cause

the one it bumped into to lend one of itsinner electrons.

Another way to see the chain reaction


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Another way to see the chain reaction.

These are the carbon atoms with their

double-bond (2 shared electrons each). The

hydrogen atoms are not shown. A collisionbreaks the first bond.

Once the first double bond is broken, a chain reaction will occur.

In about a second an entire chamber of compressed ethylene gas

turns into the polymer, polyethylene.


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Free Radical Polymerization

Initiator

Initiation

Propagation

Termination by Coupling Termination by Disproportionation


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Addition Polymerization Animation


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Addition Polymerization (PE)

n


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Polymerization of Ethene

Polyethylene can be produced through radical

polymerization, anionic addition

polymerization, ion coordination

polymerization or cationic additionpolymerization.

Ethene does not have any substituent groups

that influence the stability of the propagationhead of the polymer. Each of these methods

results in a different type of polyethylene.


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Classification of Polyethylene

Polyethylene is classified into several different

categories based mostly on its density and

branching.


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Classification of Polyethylene

Ultra high molecular weight polyethylene (UHMWPE) Ultra low molecular weight polyethylene (ULMWPE or PE-

WAX)

High molecular weight polyethylene (HMWPE)

High density polyethylene (HDPE) High density cross-linked polyethylene (HDXLPE)

Cross-linked polyethylene (PEX or XLPE)

Medium density polyethylene (MDPE)

Linear low density polyethylene (LLDPE)

Low density polyethylene (LDPE)

Very low density polyethylene (VLDPE)


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A polymer made

form just one

monomer ispolyethylene. It

is the most

common plastic.

It is used for

bottles, buckets,

jugs, containers,

toys, even

synthetic lumber,and many other

things.

There are two types of


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There are two types of

polyethylene polymers

(plastics). One is when

the polyethylene existsas long straight chains.

The picture here shows

the chains of one carbon

with two hydrogen

atoms repeating. The

chain can be as long as

20,000 carbons to35,000 carbons. This is

called high density

polyethylene (HDPE).


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When the chains

get up to 500,000carbons long, they

are tough enough

for synthetic ice,replacement joints,

and bullet-proof

vests.

There must be low density polyethylene (LDPE). It is made


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y p y y ( )

by causing the long chains of ethylene to branch. That way

they cannot lie next each other, which reduces the density

and strength of the polyethylene. This makes the plasticlighter and more flexible.

Low density polyethylene is used to make


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Low density polyethylene is used to make

plastic bags, plastic wrap, and squeeze

bottles, plus many other things.

Another polymer, which is almost the same as


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Another polymer, which is almost the same as

polyethylene, is PolyVinyl Chloride or PVC. The

difference is that every other hydrogen is replaced

with a chlorine atom (green sphere).

(CH CHCl) + O CO + CO + HCl + H O


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PVC pipes are used in our homes

and they are even handy for makinga table or chair. PVC is also used as

insulation around electric wires in the

home and the automobile.

PVC is quite safe until it burns. The

chlorines in the PVC combine with

the hydrogen atoms in the PVC to

form hydrogen chloride gas (HCl).When this contacts water in lungs or

mouth, it turns to hydrochloric acid(HCl(aq)).

(CH2CHCl)n + O2 CO2 + CO + HCl + H2O

There are many types of plastics. By controlling the


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y yp p y g

length and the branching, one can control the final

hardness or flexibility of the polymer plus qualities

like resistance to solvents, acids, or heat.

The favorite properties of plastics are that they are inert.


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p p p y

They also are durable and won't easily decay, dissolve, or

break apart. But when one throws them away, they won't

decompose.

Since they dont decompose, the answer is to recycle the


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plastics so they can be remade into something else.

The decks, fence, stepping stones, and the sweat shirt, were allmade from recycled plastic


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made from recycled plastic.

Time for Litter to Biodegrade


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Product Time to biodegrade

Paper 2-5 months

Wool socks 1 to 5 years

Plastic coated paper milk cartons 5 years

Plastic bags 10 to 20 years

Nylon fabric 30 to 40 years

Aluminum cans 80 to 100 years

Plastic 6-pack holder rings 450 years

Glass bottles 1 million years

Plastic bottles Forever

Plastic Resin Identification Codes


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Codes Descriptions Recycled products

Polyethylene terephthalate (PET, PETE) is clear, tough, and has good gas

and moisture barrier properties. Commonly used in soft drink bottlesand many injection molded. Other applications include strapping and

both food and non-food containers. Cleaned recycled PET flakes and

pellets are in great demand for spinning fiber for carpet yarns, producing

fiberfill and geo-textiles.

Fiber, tote bags, clothing, film

and sheet, food and beveragecontainers, carpet, strapping,

fleece wear, luggage and bottles.

High Density Polyethylene (HDPE) is used to make bottles for milk, juice,

water and laundry products. Unpigmented bottles are translucent, have

good barrier properties and stiffness, and are well suited to packaging

products with a short shelf life such as milk. Because HDPE has good

chemical resistance, it is used for packaging many household and

industrial chemicals.

Bottles; pipe, buckets, crates,

flower pots, garden edging, film

and sheet, recycling bins,

benches, dog houses, plastic

lumber, floor tiles, picnic tables,

fencing.

Polyvinyl Chloride or PVC has excellent chemical resistance, good

weatherability, flow characteristics and stable electrical properties. Thevinyl products can be broadly divided into rigid and flexible materials.

Bottles and packaging sheet are major rigid markets, but it is also widely

used as pipes and fittings, siding, carpet backing and windows. Flexible

vinyl is used in wire and cable insulation, film and sheet, floor coverings

synthetic leather products, coatings, blood bags, medical tubing and

many others.

Packaging, binders, decking,

paneling, gutters, mud flaps, filmand sheet, floor tiles and

resilient flooring, cables, mats,

cassette trays, electrical traffic

cones, boxes, garden hose,

mobile.

Plastic Resin Identification Codes


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Codes Descriptions Recycled products

Low Density Polyethylene (LDPE) used predominately in film applications

due to its toughness, flexibility and relative transparency, making it popular

for use in applications where heat sealing is necessary. LDPE is also used to

manufacture some flexible lids and bottles and it is used in wire and cable

applications.

Shipping envelopes, garbage

can liners, film and sheet,

furniture, compost bins,

paneling, trash cans, landscape

timber, lumber

Polypropylene (PP) has good chemical resistance, is strong, and has a high

melting point making it good for hot-fill liquids. PP is found in flexible and

rigid packaging to fibers and large molded parts for automotive and

consumer products.

Automobile battery cases,

signal lights, battery cables,

brooms, brushes, oil bins,

funnels, bicycle racks, trays

pallets, sheeting.

Polystyrene (PS) is a versatile plastic that can be rigid or foamed. General

purpose polystyrene is clear, hard and brittle. It has a relatively low

melting point. Typical applications include protective packaging,

containers, lids, cups, bottles and trays.

Light switch plates, vents,

thermal insulation, desk trays,

rulers, license plate frames,

foam packing, foam plates,

utensils

Other. Use of this code indicates that the package in question is made with

a resin other than the six listed above, or is made of more than one resin

listed above, and used in a multi-layer combination.

Bottles, plastic lumber

Molecular Weight as a Function of


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g

Conversion

Average molecular weight builds upslowly and a high molecular weight isformed only when conversion is more

than 98%nmer + monomer (n+1) mernmer + mmer (n+ m) mer

Fast initiation process coupled withabsence of termination reaction

Very fast mechanism, full sizedpolymer formed instantaneously afterinitiation, thus polymer size isindependent of reaction time


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Comparison ofStep Growth

and Chain

Growth

Polymerization

Eff t f St t P ti


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Effect of Structure on Properties

Physical properties affected by:

Chemical composition

Arrangement of chains

Molecular weight

Eff t f M l l W i ht


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Effect of Molecular Weight

Eff t f C iti


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Effect of Composition

Flexible

Rigid

Effect of Side Chain Substitution,


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,

Crosslinking and Branching on PE

i f l


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Comparison of Polymers

Polymer Behavior


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y

1) Thermoplastic polymers can be formed at elevated

temperatures, cooled and then reheated andreformed into another shape without changing the

structure or properties of the polymer. These are

obviously easily recycled.

2) Thermosetting polymers are network polymers often

formed by condensation reactions. They are

generally stronger than thermoplastic polymers but

they can not be reprocessed easily or at all.3) Elastomers or rubbers have an intermediate behavior

with the ability to deform enormous amounts without

permanent change in shape.

Thermoplastic vs Thermoset


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Heating and cooling cycle of

thermoplastic

Cross-linked moleculesLong chain molecules

Heating and cooling cycle of

thermosetting plastic

Thermoplastic vs Thermoset


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Molecular Shape


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Molecular Shape

The angle between the singly bonded carbonatoms is ~109o carbon atoms form a zigzag

pattern in a polymer molecule

Molecular Shape


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Molecular Shape

Moreover, while maintaining the 109o anglebetween bonds polymer chains can rotate

around single C-C bonds (double and triple

bonds are very rigid). Random kinks and coils lead

to entanglement, like in the spaghetti structure:

Molecular Shape


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Molecular Shape

Molecular chains may thus bend, coil and kink

Neighboring chains may intertwine and

entangle

Large elastic extensions ofrubbers correspond

to unraveling of these coiled chains

Mechanical / thermal characteristics depend

on the ability of chain segments to rotate

If you want to produce nylon 6,6 by condensation


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polymerization using hexamethylene diamine and

adipic acid, what masses of these two components will

be needed to yield 20 kg of completely linear nylon 6,6?

We write down the molecular weights of the three substances and

calculate their masses in the ratio of their molecular weights:

MW(adipic acid) = 146 g/mol

MW(hexamethylene diamine) = 116.21 g/mol

MW of Nylon 6,6 Repeat unit = 226 g/mol

Weight of polymer produced = 20 kg = 20000g

n = m/MM Hence mass of adipic acid needed = 88.5 x 146 = 12921 g = 12.9 kg

and mass of hexamethylene diamine needed = 88.5 x 116 = 10266 g =

10.26 kg


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Which has a greater volume and a lower Tg

a) HDPE b) LDPE, Why?

LDPE


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What is the approximate bond angle of carbon atom in

a) linear b) crosslinked polymer?

109.5o


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Which will be more flexible

a) poly(ethylene terephthalate) b) poly(butyleneterephthalate), Why?

poly(butylene terephthalate)


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Which will have higher Tg

a) PMMA b) PBMA, Why?

PMMA


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Which will have higher Tg

a) isotactic PP b) atactic PP, Why?

isotactic PP


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Which will be more permeable to gas at room

temperature a) isotactic PP b) atactic PP, Why?

atactic PP


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Which will be more flexible

a) PMMA b) PMA, Why?

PMA

The PMA chains are more

flexible than PMMA chains

due to the reason that

bulkier methyl groups on

PMMA hinder packing of

chains and hence make itrigid. For reference see this table alsoconsult the literature (hard copy) provided

in last lecture.

PMAPMMA

Flexible low TmRigid high Tm


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Which will have higher Tm

a) Nylon b) Aramid, Why?

Aramid


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What is the type of hydrogen bond present in globular

protein?

Intramolecular hydrogen bond


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Which will be more transparent

a) a-PS b) Isotatic PP, Why?

a-PS

Thermoset


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A thermosetting plastic, also known as a thermoset, is polymer material that in

a soft solid or viscous state changes irreversibly into an hard, insoluble polymer

network by curing (cross-linking). Curing can be induced by the action ofheator suitable radiation, or both. A cured thermosetting polymer is called a

thermoset. E.g. Vulcanized rubber, Epoxy resin.

Natural Rubber

For a rubber component that, in its

fi l f i b l i d


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final form is to be vulcanized,

should vulcanization be carried outprior or subsequent to the forming

operation? Why?

Vulcanization of a rubber component should

be carried out prior to the forming operation

since, once it has been vulcanized, plasticdeformation (and thus forming) is not possible

since chain crosslinks have been introduced.

For the following pair of polymers, do the following: (1) state

whether or not it is possible to decide if one polymer has a


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whether or not it is possible to decide if one polymer has a

higher tensile strength than the other; (2) if this is

possible, note which has the higher tensile strength and then

cite the reason(s) for your choice.

Syndiotactic polystyrene having a number-average molecular

weight of 600,000 g/mol

Isotactic polystyrene having a number-average molecular weight

of500,000 g/mol.

Yes, it is possible. The syndiotactic polystyrene has the higher tensile

strength. Both syndiotactic and isotactic polymers tend to

crystallize, and, therefore, we assume that both materials have

approximately the same crystallinity. However, tensile modulusincreases with increasing molecular weight, and the syndiotactic PS

has the higher molecular weight (600,000 g/mol versus 500,000

g/mol for the isotactic material).

Epoxy Thermoset


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Epoxy Thermoset

Epoxide group3-D Network


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RT Curing

of Epoxies
http://en.wikipedia.org/wiki/File:Epoxy_prepolymer_chemical_structure.png


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Epoxy

Thermoset

Diglycidyl ether of

bisphenol A

Thermoset Plastic Manufacturing
http://en.wikipedia.org/wiki/File:Epoxy_prepolymer_chemical_structure.png


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g

Thermoset plastic industrial process is identified by three

stages: A, B and C.

A-stage refers to the key raw materials uncured stage

B-stage refers to the product produced when curing agent

and resin are brought together and leave a dry semi-cured

resin.

C-stage refers to the fully cured stage".

Phenol Formaldehyde


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Phenol Formaldehyde

Urea Formaldehyde Amino Resin


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y

Melamine Formaldehyde
http://upload.wikimedia.org/wikipedia/commons/2/2a/Ladle_melamine_18j07.JPGhttp://upload.wikimedia.org/wikipedia/commons/b/b1/Melamine_formaldehyde_polymer.png


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Extension and Curing ofPolyurethane


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Polyurethane

Network Glyptal Resin


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Network Glyptal Resin


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Preparation

and Curing

of VinylEster


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Typical Addition

Polymers(Homopolymers)

Typical Condensation Polymers


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Some High PerformanceCondensation Polymers


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Condensation Polymers


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Examples of addition thermoplastics


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Molecular Structure


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1 Linear polymers: Van der Waals bondingbetween chains. Examples: polyethylene,

nylon.

2 Branched polymers: Chain packing efficiency is

reduced compared to linear polymers - lower

density

Molecular Structure


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3 Cross-linked polymers: Chains are connectedby covalent bonds. Often achieved by adding

atoms or molecules that form covalent links

between chains. Many rubbers have this

structure.

Molecular Structure


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4 Network polymers: 3D networks made fromtrifunctional mers. Examples: epoxies,

phenolformaldehyde

Isomerism


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Isomerism

Two types of isomerism are possible:

stereoisomerism and geometrical isomerism

Stereoisomerism: atoms are linked together in

the same order, but can have different spatial

arrangement

Geometrical Isomerism


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Two carbon atoms bonded by a double bondin a chain. H atom or radical R bonded to

these two atoms can be on the same side of

the chain (cis structure) or on opposite sides

of the chain (trans structure).

cis-polyisoprene (Natural Rubber) trans-polyisoprene (gutta percha)

Head/Tail Configuration


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In vinyl polymers

Normally linked in a head to tail

configuration

-substituents are separated by

three carbon atoms

In head to head configuration this

separation is only by 2 carbon

atoms

The separation with tail to tail

configuration is by 4 atoms

Degree of Polymerization
http://upload.wikimedia.org/wikipedia/commons/f/f6/Tail_head_isomerism.svghttp://upload.wikimedia.org/wikipedia/commons/f/f6/Tail_head_isomerism.svghttp://upload.wikimedia.org/wikipedia/commons/f/f6/Tail_head_isomerism.svghttp://upload.wikimedia.org/wikipedia/commons/f/f6/Tail_head_isomerism.svg


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The polymerization reaction is often characterized by its

degree of polymerization, given by,

unitrepeatofweightmolecular

polymerofweightmolecularDPtion,polymerizaofDegree

531226

120,000DP

g/mol120,000ightpolymer we

g/mol226unitrepeat

6,6Nylon

example,For

Molecular Weight


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g

MW = DP X (MW)u

TT

T

TT

T

Broad MWD

Narrow MWD

P1

P2

Molecular Weight


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Each MW can be represented as Mi

Ni= number of molecules of MW = Mi

wi= weight fraction of given system of chains

with MW = Mi

Molecular Weight


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Polydispersity can bemeasured by PDI

(polydispersity index):

z = 1.03 or 1.05 is

considered close tomonodisperse


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Impact of Molecular Weight on

Material Properties


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Material PropertiesIncreasing Degree of Polymerization, DP

Summary: Size Shape -Structure


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Microscopic Properties

(I l l I i )


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(Intermolecular Interactions)

Chain entanglementamorphous

Chain orderingCrystallinity, Liquid Crystalline

Phase separations (microdomains)

Morphology

Types of Intermolecular Forces


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Macroscopic Properties

(Physical Behavior)


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(Physical Behavior)

Tensile and/or Compressive Strength Elasticity

Toughness

Thermal Stability Flammability and Flame Resistance

Degradability

Solvent Resistance

Permeability

Ductility (Melt Flow)

Polymer Crystallinity


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Atomic

arrangement in

polymer

crystals is more

complex thanin metals or

ceramics (unit

cells aretypically large

and complex).Polyethylene



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Polymer moleculesare often partially

crystalline

(semicrystalline),with crystalline

regions dispersed

within amorphous

material.

Factors for Polymer Crystallinity


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Rate of cooling during solidification:

time is necessary for chains to move and align into a

crystal structure

Mer complexity:

crystallization less likely in complex structures, simplepolymers, such as polyethylene, crystallize relatively easily

Chain configuration:

linear polymers crystallize relatively easily, branches

inhibit crystallization, network polymers almost

completely amorphous, crosslinked polymers can be both

crystalline and amorphous

Factors for Polymer Crystallinity


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Isomerism: isotactic, syndiotactic polymers

crystallize relatively easily - geometrical regularityallows chains to fit together, atactic difficult to

crystallize

Copolymerism: easier to crystallize if merarrangements are more regular - alternating, block

can crystallize more easily as compared to random

and graft

More crystallinity: higher density, more strength,

higher resistance to dissolution and softening by

heating



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Crystalline polymers are denser thanamorphous polymers,

so the degree of crystallinity can be obtained

from the measurement of density:

c: Density of perfect crystalline polymer a: Density of completely amorphous polymer

s: Density of partially crystalline polymer that is analyzed


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Polymer Crystals


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Thin crystalline platelets grown from solution

Chains fold back and forth: chain-folded

model

The average chain length is much greater than

the thickness of the crystallite

Polyethylene single crystal

Polymer Crystals


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Spherulites: Aggregates of

lamellar crystallites ~ 10 nmthick, separated by amorphous

material.

Aggregates approximately

spherical in shape.

Photomicrograph of spherulite

structure of polyethylene

Tie-chain molecules that act as connecting

links between adjacent lamellae pass

through these amorphous regions.

Number Eighty Eight


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HUMAN APOLIPOPROTEIN A-I. the major proteincomponent of high-density lipoproteinBiopolymers can be complex and nice

CHAPERONE/STRUCTURALPROTEIN


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D. Choudhury, A Thompson, V. Stojanoff, S. Langermann, J.

Pinkner, S.J. Hultgren and S. D.

Knight (1999). X-ray

structure of the FimC-FimHchaperone-adhesin complex

from uropathogenic

Escherichia coli. Science, 285:

1061-1066.Chaperones are proteins that assist the non-covalent

folding or unfolding and the assembly or disassembly of

other macromolecular structure.


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Summary

Documents

Polymer Introduction