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Summary of lecture
• basic chemical names• addition polymers
o configuration/conformationo stereoregularity/tacticityo crystalline or amorphouso transition temperatures
• condensation polymers• ring-opening polymers
Naming basic chemicalsNumberC atoms
Prefix single bond
double bond
triple bond
1 Meth- -ane
2 Eth- -ane -ene -yne
3 Prop- -ane -ene -yne
4 But- -ane -ene -yne
5 Pent- -ane -ene -yne
6 Hex- -ane -ene -yne
7 Hept- -ane -ene -yne
8 Oct- -ane -ene -yne
9 Non- -ane -ene -yne
10 Dec- -ane -ene -yne
Basic chemicalsC atoms Name Formula CnH2n+2 Boiling
point
1 Methane CH4 -164°C (gas)
2 Ethane C2H6 -89°C (gas)
3 Propane C3H8 -42°C (gas)
4 Butane C4H10 -0.5°C (gas)
5 Pentane C5H12 36°C (liquid)
6 Hexane C6H14 69°C (liquid)
7 Heptane C7H16 98°C (liquid)
8 Octane C8H18 125°C (liquid)
9 Nonane C9H20 151°C (liquid)
10 Decane C10H22 174°C (liquid)
Paraffins/waxes
C20H42 melts at 37 °C quasi-solid
1000+ Polyethylene H[CH2]nH solid
Transition temperature data from http://www.elmhurst.edu/~chm/vchembook/501hcboilingpts.html
Bond rotation
• Movie of rotation about a single bondo file taken from
http://plc.cwru.edu/tutorial/enhanced/files/polymers/struct/bond.mov
• Movie of rotation with different side groupso file taken from
http://plc.cwru.edu/tutorial/enhanced/files/polymers/struct/conform.swf
Chemical Groups (reactants)
• Acid
• Alcohol
• Amine
• NB: nitrogen in amine has a free p-orbital
which can become part of a π-bond
HN
H
CO
O H
HO
Polymers• Polymers are class of materials where many small molecules (monomers) are linked together by covalent bonds to form long chains or networks• an alternative name for polymers is macromolecules• a homopolymer has only 1 repeating unit• a copolymer has 2 different repeating units• a terpolymer has 3 different repeating units.
Polymers
• Thermoplastic - usually long straight chainssometimes with short brancheso copolymers AB (and terpolymers ABC) can be
alternating ---ABABABABAB--- block ---AAABBAAABB--- graft (type B branches on type A backbone) random ---AABABBBAAB---
• Thermoset - usually 3-dimensional networks• Elastomers - 3-D networks with sparse
interlinks between chains (e.g. rubber)
Addition polymers• reaction by opening double bonds• all atoms from reactants end up in the product
• n CH2=CHX reacts to become [- CH2-CHX-]n
o if X = H, the polymer is polyethyleneo if X = CH3, the polymer is polypropylene
o if X = Cl, the polymer is polyvinylchlorideo if X = C6H5, the polymer is polystyrene
o ... this list is not exhaustiveo if monomer is CF2=CF2,
the polymer is polytetrafluoroethylene
Configuration/Conformation• Configuration
o the arrangements of atoms on the polymer chaino fixed relative positions of atoms
• Conformationo the arrangement of the atoms in spaceo regular linear chains can crystalliseo branched/bulky side-groups or irregular
copolymers have longer repeat units and are thus less likely to crystallisebut more likely to be amorphous
Stereoregularity -> tacticity
• Isotactico characteristic groups
all on the same sideof the polymer chain
• Syndiotactico characteristic groups
on alternate sidesalong polymer chain
• Atactic - characteristic groups located atrandom along the polymer chaino images from
http://plc.cwru.edu/tutorial/enhanced/files/polymers/struct/Struct.htm
Crystalline vs amorphous• Crystalline polymers
o molecules pack more closely leading to: higher density better mechanical properties (more bonds/m3) better resistance to environmental degradation
o NB: common polymers are partially crystalline crystallites distributed in an amorphous matrix
• Amorphous polymerso random configuration
reduced properties re. crystalline materials transparent to white light (e.g. PS, PC, PMMA)
Crystallinity
• Two model structures have been proposed
• Images fromhttp://chem.chem.rochester.edu/~chem421/cryst.htmhttp://www.pslc.ws/mactest/crystal.htm respectively
Fringed micelle Folded lamella
Transition temperatures
• Tg = Glass transition temperatureo segmental motion is frozen outo brittle elastic below Tg
o tough/viscoelastic above Tg
• Tm = Crystalline melting pointo only occurs in crystallites
• both temperatures may be a rangerather than a specific temperature
Transition temperatures
Specifi
c volu
me
Temperature
Crystalline solid
Amorphous/glassy
Liquid
Ru
bb
er
y
Tg Tm
Condensation polymers
• XOH + HY XY + H2O
• HOXOH + HYH HOXYH + H2Oo further reactions with HOXOH and HYH
will produce a linear molecule
Condensation polymers• Acid + base salt + water
o HCl + NaOH NaCl + H2O
• Acid + alcohol ester + watero R.C=O.OH + HO.R’ R.C=O.O.R’ + H2O
• Acid + amine amide + watero R.C=O.OH + H2N.R’ R.C=O.HN.R’ + H2O
• If two reactive sites on each molecule,then a polymer chain will result
Ring-opening polymers
• HOXOH + HYH HOXYH +H2Oo further reactions with HOXOH and HYH
will produce a linear molecule
• HOXH + HOXH HOXXH +H2Oo i.e. both reactants might be on one moleculeo but such a system could react with itself
to form a cyclic molecule if X > 4C atomso such a cyclic molecule can polymerise
without loss of water(H2O already removed in cyclisation reaction)
Ring-opening polymers
• Ring-opening polymerisationduring composite manufacture has potential to produce thermoplastic matrix composites from RTM/RIFTo caprolactam to produce polyamide 6
(e.g. DSM Fiber Intermediates APA-6),o laurolactam to produce polyamide 12
(e.g. EMS-Grivory APLC12), and o cyclic butylene terephthalate oligomers to
produce PBT polyester (e.g. Cyclics Corporation).
Voluntary Plastic Container Coding System
• proposed by Society for the Plastics Industry (SPI) in the United States of America
• remember Tm = Tg + 200°C (±~50°C) so some common thermoplastics are.....
n
abc
Polymer
Acronym
Coding Tg (ºC) Tm (ºC) Morphlg
y
Low-density polyethylene
LDPE 4 -130 +105 crystalline
High-density polyethylene
HDPE 2 -125 +135 crystalline
Polypropylene PP 5 -27 .. -10 +165 ..
+170crystalline
Polyamide (nylon) 6,6 PA6,6 7 +55 +255 crystalline
Polyvinylchloride PVC (V) 3 +75 ..
+80-- amorphou
sPolystyrene PS 6 +90 ..
+100 -- amorphous
Polyethylene terephthalate
PET (PETE)
1 +67 .. +80
265 crystalline
Polycarbonate PC 7 +145 ..
+150 -- amorphous
Polyoxymethyle
ne (acetal) POM 7 < -150 +180 crystalline
Polyurethane PU 7 +140 -- amorphou
sPoly ether ether ketone
PEEK 7 +144 367 crystalline
Periodic Table of Thermoplastics(Tangram Technology)http://polymer.w9of.com/wp-content/uploads/2011/01/Polymer-Periodic-Table.pdf