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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
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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.html8/12/2019 Lecture 1.0 - Polymer Classification
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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