Thermoplastic polymers processed by a heat-form-cool cycle John Summerscales.

Thermoplastic polymersprocessed by a heat-form-cool cycle

John Summerscales

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

Geometric isomers

• cis:

• trans:

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

Chemical Groups (products)• Ester

• Amide

• Ether

CO

O

CO

NH

O

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

Summary of thermoplastics lecture• basic chemical names• addition polymers

o configuration/conformationo stereoregularity/tacticityo crystalline or amorphouso transition temperatures

• condensation polymers• ring-opening polymers