lecture 1.0 - polymer classification

8/12/2019 Lecture 1.0 - Polymer Classification

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Introduction

n


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ISSUES TO ADDRESS...

What are the basic

Classification?

Monomers and chemical groups?

Nomenclature?

Polymerization methods?Molecular Weight and Degree of Polymerization?

Molecular Structures?

Crystallinity?

Microstructural features?

Polymer


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Students should:

Be able to understand the concept of polymerisation

Be able to differentiate/ distinguish between thermoplastic,thermoset and elastomer

Be able to describe the two basic methods of polymerization of

thermoplastic and thermoset materials

Understand the difference between a homopolymer, copolymer,alloy, and blend

Be able to name the polymer Understand how molecular weight can affect the properties of thematerial


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1.0 BASIC POLYMER CHEMISTRY

Plastics vs Polymers

Polymer = long chain molecule (poly + mer;Greek)

Thermoset vs Thermoplastic

Commodity vs Engineering plastics

(Nearly) all are petrochemical based


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Polymers - long chain molecules of highmolecular weight

n State Use

1-4 gas burned for energy

5-11 liquid gasoline

9-16 med. visc.liquid

kerosene

16-25 hi visc. liq. oil, grease

25-50 solid paraffin wax

1000-3000

tough plastic PE bottles, containers


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Hydrocarbons

at Room Temperature Gas Methane

Ethane

Propane Butane

Plastic Liquid Waxy

20 to 40

Carbons5 to 19

Carbons

40 or more

Carbons


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Polymer, Macromolecule and Polymerization

In strict term, apolymeris a substancecomposed of

molecules which have long sequences of one or more

species of atoms or groups of atoms linked to each other by

primary, usually covalent, bonds.

Macromoleculesare formed by linking together monomer

molecules through chemical reactions, the process by which

this is achieved being known aspolymerization.

Although the wordspolymerand macromoleculeare usuallyinterchangeably, the latter strictly defines the molecules of

which the former is composed.


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BASIC POLYMER CHEMISTRY

HYDROCARBONS & POLYMERS Based on the carbon atom

Form 4 bonds with other atoms (valence)

Joins to itself to form long chains & other shapes

Polymerization results from this:

Ethylene -> polyethylene

Propylene -> polypropylene

Styrene -> polystyrene

Vinyl chloride -> polyvinyl chloride


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BASIC POLYMER CHEMISTRY

HYDROCARBONS & POLYMERS


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What Makes Polymers Unique? Really big molecules (macromolecules) like polymers have

very different properties than small molecules

Chain entanglement: Long

polymer chains get entangled with

each other.


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Melting Point As the length of hydrocarbons get longer, theMelting Pointgrows Higher. Why?

-300

-200

-100

0

100

200

300

400

500

600

0 5 10 15 20 25 30 35 40 45

Tempurature(C)

Number of Carbons

Melting and Boiling Temperatures of Alkanes

Boiling Point (C)

Melting Point(C)


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What other material propertieschange?

Viscosity

Hardness

Toughness

Flammability


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Bonding

Covalent

Ionic (NaCl)

Polar (H2O)

Van der Waals


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Polymers

As Broad as in Daily Life:synthetic polymers

polystyrene c is-polyisoprene poly(vinyl pyrrolidone)

polycarbonate poly(vinyl chloride)


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Low-Density Polyethylene (LDPE)

Chain Length: 1000 - 2000


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High-Density Polyethylene (HDPE)

Chain Length: 10,000100,000


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Ultra-high-molecular-weightpolyethylene (UHMWPE)

Helmet

Gears

Joint

Replacement

Chain Length: 2-6 million


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PVC(polyvinyl chloride)Chain Length: 4,0005,000

More Polar Stronger Bonding


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Polyethylene Terephthalate (PETE)

Polyester

Chain Length: 4,0008,000

Ester
http://upload.wikimedia.org/wikipedia/commons/c/cd/SEMexample.jpg


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Nylon


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Cotton

Long Strands of Cellulose

+ Hydrogen Bonds

Cellulose is the most common organic material on earth!

It is also a primary constituent of wood and paper.


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Polymers in

BiologyDNA

Sugar

Starch

Proteins


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Polymer (Thermoset) : reinforced with fibres to form

composite materials (use in

aerospace and automotive industries)

structural adhesive e.g for joining

composite

- surface coating

- electrical and furnitureindustries

crack sealing and repair
http://www.hydrocarbons-technology.com/contractors/pipeline/citadel/citadel3.htmlhttp://www.hydrocarbons-technology.com/contractors/pipeline/citadel/citadel1.htmlhttp://www.hydrocarbons-technology.com/contractors/pipeline/citadel/citadel3.htmlhttp://www.hydrocarbons-technology.com/contractors/pipeline/citadel/citadel1.html


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Kevlar

Strong Network of Covalent Bonds

And Polar Hydrogen Bonds


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1.1 CLASIFICATION


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Classi f icat ion of p olymers

Polymers can be assigned to three groups based on their:Response towards heat or processing

characteristics.

Polymerization mechanism.

Response tow ards heat

Polymers can de divided into two major groups based on

their thermal processing behaviour:

Thermoplastics

Thermosets


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Synthetic Polymers

(Based on Properties)

Thermoplastics Elastomers Thermosets

e.g.

polystyrene

(amorphous),

Polyethylene

(crystalline),

etc.

e.g.

phenol

resin,epoxy

resin, etc.

ThermoplasticElastomers (TPE)

VulcanizedElastomers

e.g.

polystyrene-b-

poly

butadiene-b-polystyrene

(Kraton)

e.g.

styrene-

butadiene

rubber(SBR)


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Classi f icat ion o f polym ers (cont.)

Response towards heat (cont.)

Thermoplastics

Can be heat-softened in order to process into a desired

form.

Can be melt-processed by a variety of methodsincluding extrusion and molding.

Waste thermoplastics can be recovered and

refabricated by heat and pressure.

E.g, Polystyrene, polyethylene, polypropylene, PVC

Applicationsfilm for packaging, photographic and

magnetic tape, beverage and trash containers,

automotive parts and upholstery.


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Classi f icat ion o f polym ers (cont.)

Response towards heat (cont.)Thermosets

Individual chains have been chemically linked by

covalent bond during polymerization or fabrication

These cross-linked networks resist heat softening,

creep, and solvent attack. Cant be thermally

processed.

E.g. Epoxy, phenol-formaldehyde resins, andunsaturated polyesters.

Applicationssuitable materials for composite,

coatings, adhesive.


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Synthetic Polymers

(Based on First Order Structures)

Homopolymers Copolymers Polymer Blends and IPNs-A-A-A-A-A-A-A-A- polyA + polyB

Statistical

Copolymers-B-B-A-B-A-A-B-

Alternating

Copolymers-A-B-A-B-A-B-A-B-

Graft

Copolymers-A-A-A-A-A-A-A-A-

BB

B

Block

Copolymers-A-A-A-A-B-B-B-B-

-A-A-A-B-B-B-A-A-A- BB

B

Homopolymer:Formal definition: a polymer derived from one species of monomer.

Structure-based definition: a polymer whose structure can be represented by

multiple repetition of single type of repeat unit which may contain one or more

species of monomer units (structural units).Copolymer:Formal definition: a polymer derived from more than one species of

monomer. Structure-based definition: a polymer whose molecule contains two or

more different types of repeat unit (polymers such as PET, Nylon are usually

considered as homopolymers.)

Polymer Blends and IPNs:Linked together through secondary (physical) forces.

IPNs: interpenetration polymer networks.

Cascade

polymers-

dendrimers

???


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Copolymers

two or more monomers

polymerized together randomA and B randomly vary

in chain

alternatingA and B alternate inpolymer chain

blocklarge blocks of A alternatewith large blocks of B

graftchains of B grafted on to Abackbone

A

B

random

block

graft

alternating


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Homopolymer of PP-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-

H H H H H H H H H H H H H H H

H cH3 H cH3 H cH3 H cH3 H cH3 H cH3 H cH3 H

-c-c-c-c-c-c-c-c-c-c-c-c-c-c-c-H H H H H H H H H H H H H H H

H cH3 H cH3 H cH3 H H H H H H H H HCopolymer of PP

PP-PP-PP-PP-PP-PE-PE-PE-PE-PEBlock Copolymer of PP

Random Copolymer of PP PP-PE-PP-PP-PP-PE-PE-PP-PE-PE

EXAMPLE: POLYPROPYLENE (PP)


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Thermoset vs. Thermoplastic

Thermoplastics can be repeatedly

reheated and molded into shapes on

cooling

Thermosetting plastics when reheated

decompose


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1.2 POLYMERIZATION

a. Addition Polymerization; Most packaging plastics

Needs the correct conditions of temperature & pressure

Catalysts & promoters aid the process

b. Condensation Polymerization;

PET & polyamide (nylon)

Joins 2 reactive monomers and releases water

c. Rearrangementmonomers link togetherwithout losing any atoms, but rearrange

themselves


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Covalent chainconfigurations and strength:

Direction of increasing strengthAdapted from Fig. 14.7, Callister 6e.

Polymer Microstructure

Van der Waals, HMore rigid


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Main Categories of Polymers:

Plastics:

Thermoplasticscan be remelted:

Engineered Thermoplastics

Commodity Thermoplastics

Thermosetting Plasticscan not be remelted

Engineered Thermosets

Commodity Thermosets Elastomers:

Thermosets and thermoplastic!!


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Commodity Thermoplastics

Commodity: Polyethylene (PE), Polystyrene (PS),Polypropylene (PP), Polyvinyl Chloride (PVC orvinyl) 80% of all thermoplastics!!

Also, Styrene Acrylonitrile (SAN) the copolymerwe tested in lab

Flows at elevated temperatures.

Has a glass transition temperature.

Long polymer chains

Can be remelted and recycled.


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Engineering Thermoplastics

Engineering Plastics: Polycarbonate (PC),Acrylonitrile-butadiene-styrene (ABS),Polyamide (Nylons, PA)

Engineered plastics account for about 10%of all plastic usage.

Generally have higher tensile strength and

elongation than commodity plastics


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Elastomers

Butyl, natural rubber (polyisoprene),EPDM, neoprene, nitrile, etc..

Characterized by high deformation(extremely flexible) generally greater than100%.

Almost all are thermosetting with

exception of TPEs


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Vulcanization


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Thermoset

Materials

Cross-linked

Phenol-formaldehyde

Unsaturated polyesters

Epoxide resins

Amino-formaldehydes

Natural rubber

Synthetic rubbers

Thermoplastic elastomers

Urea-formaldehydes


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MaterialsThermosets (PF, UF, MF)

Bakelite radio 1930 Picnic set (UF) 1940s

Adhesives and impregnating resins

Electrical fittings

Tableware/picnicware

Kettle/iron/soucepan handles

Decorative laminates for work surfaces

Parts for domestic appliences

Thermoset


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Materials

Thermosets (GRP, Epoxy resin)

Blondecell Risho

Marine mouldings Aircraft components

Sports equipment

Racing car components

Adhesives Electrical insulators+

Thermoset

1 3 Nomenclature


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A. Types of Nomenclature

a. Source name: to be based on names of corresponding monomer

Polyethylene, Poly(vinyl chloride), Poly(ethylene oxide)

b. IUPAC name: to be based on CRU, systematic name

Poly(methylene), Poly(1-chloroethylene), Poly(oxyethylene)

c. Functional group name:

Acoording to name of functional group in the polymer backbone

Polyamide, Polyester

1.3 Nomenclature


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d. Trade name: The commercial names by manufacturer Teflon, Nylon

e. Abbreviation name: PVC, PET

f. Complex and Network polymer: Phenol-formaldehyde polymer

g. Vinyl polymer: Polyolefin

Nomenclature

1 3 1 Vi l l


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1.3.1 Vinyl polymers

A. Vinyl polymers

a. Source name: Polystyrene, Poly(acrylic acid),

Poly(-methyl styrene), Poly(1-pentene)

b. IUPAC name: Poly(1-phenylethylene), Poly(1-carboxylatoethylene)

Poly(1-methyl-1-phenylethylene), Poly(1-propylethylene)

CH2CH

Polystyrene Poly(acrylic acid)

Poly(-methylstyrene) Poly(1-pentene)

CH2C

CH3

CH2CH

CO2H

CH2CH

CH2CH2CH3

1 3 1 Vi l l


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B. Diene monomers

Source name: 1,2-Poly(1,3-butadiene) 1,4-Poly(1,3-butadiene)

IUPAC name: Poly(1-vinylethylene) Poly(1-butene-1,4-diyl)

CH2CH CHCH2CH2CH

HC CH2

1,2-addition 1,4-addition

1.3.1 Vinyl polymers

1 3 2 Vi l l


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1.3.2 Vinyl copolymer

SystematicPoly[styrene-co-(methyl methacrylate)]

Poly[styrene-alt-(methyl methacrylate)]

Polystyrene-block-poly(methyl methacrylate)

Polystyrene-graft-poly(methyl methacrylate)

Concise

Copoly(styrene/methyl methacrylate)

Alt-copoly(styrene/methyl methacrylate)

Block-copoly(styrene/methyl methacrylate)Graft-copoly(styrene/methyl methacrylate)


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Additives


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Polymers

Materials

Additives

Fillers Plasticizers

Stabilizers

Flame retardants

Colorants

Lubricants

Antistatic agents


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Polymers

Materials

Properties

Lightness

High strength-to weight ratio

High strength composites Low thermal conductivity

Low electrical conductivity

Resistance to chemicals

Variety of colours and transparencies

Low cost

Recyclability

Flammability

Static electrification


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RECYCLING

The favorite properties of plastics are that they are inert and won't


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e a o e p ope es o p as cs a e a ey a e e a d o

react with what is stored in them. They also are durable and won't

easily decay, dissolve, or break apart. These are great qualities

for things you keep, but when you throw them away, they won't

decompose.

Since they dont decompose the answer is to recycle


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Since they don t decompose, the answer is to recycle

the plastics so they can be remade into something

else. Here we see a bunch of CDs getting recycled.

The decks, fence, stepping stones, house shingles, and the


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pp g gsweat shirt, were all made from recycled plastic.


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RECAPThermoplastic molecules are long strands or chains of atoms.

Smaller atoms or groups of atoms (mers) are linked together to formthe long chains so that they are many units long.

(many mers polymer)

This long length to diameter or high aspect ratio gives polymeric

materials very distinctive properties like high strength with verylight weight.

The reason for these properties is that the polymer chains are heldtogether due to ENTANGLEMENT. The chains have a hard timesliding past each other like tangled hair.

The polymer chains do not share chemical bonds with each other. Ifthey did, they would be crosslinked and would not melt whenreheated.


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Entanglement isnt the only thing that holds the molecules together,there are charges on the molecules that attract the othermolecules (polar forces), and weak attractive forces between the

molecules (secondary forces sometimes called Van der Waalsforces.)

The two main polymerization methods or reactions used to create

polymer chains are:

ADDITION and CONDENSATION

REACTIONS

lecture 1.0 - polymer classification

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