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

Summary of lecture basic chemical names addition polymers configuration/conformation stereoregularity/tacticity crystalline or amorphous transition temperatures condensation polymers ring-opening polymers

Naming basic chemicals Number C atoms Prefix single bond double bond triple bond 1 Meth- -ane 2 Eth- -ene -yne 3 Prop- 4 But- 5 Pent- 6 Hex- 7 Hept- 8 Oct- 9 Non- 10 Dec-

Basic chemicals C atoms Name Formula CnH2n+2 Boiling point 1 Methane -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 bond file taken from http://plc.cwru.edu/tutorial/enhanced/files/polymers/struct/bond.mov Movie of rotation with different side groups 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 C O H HO H N

Chemical Groups (products) Ester Amide Ether C O C O N H 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 chains sometimes with short branches 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 if X = H, the polymer is polyethylene if X = CH3, the polymer is polypropylene if X = Cl, the polymer is polyvinylchloride if X = C6H5, the polymer is polystyrene ... this list is not exhaustive if monomer is CF2=CF2, the polymer is polytetrafluoroethylene

Configuration/Conformation the arrangements of atoms on the polymer chain fixed relative positions of atoms Conformation the arrangement of the atoms in space regular linear chains can crystallise branched/bulky side-groups or irregular copolymers have longer repeat units and are thus less likely to crystallise but more likely to be amorphous

Stereoregularity -> tacticity Isotactic characteristic groups all on the same side of the polymer chain Syndiotactic characteristic groups on alternate sides along polymer chain Atactic - characteristic groups located at random along the polymer chain images from http://plc.cwru.edu/tutorial/enhanced/files/polymers/struct/Struct.htm

Crystalline vs amorphous Crystalline polymers molecules pack more closely leading to: higher density better mechanical properties (more bonds/m3) better resistance to environmental degradation NB: common polymers are partially crystalline crystallites distributed in an amorphous matrix Amorphous polymers random configuration reduced properties re. crystalline materials transparent to white light (e.g. PS, PC, PMMA)

Crystallinity Two model structures have been proposed Images from http://chem.chem.rochester.edu/~chem421/cryst.htm http://www.pslc.ws/mactest/crystal.htm respectively Fringed micelle Folded lamella

Transition temperatures Tg = Glass transition temperature segmental motion is frozen out brittle elastic below Tg tough/viscoelastic above Tg Tm = Crystalline melting point only occurs in crystallites both temperatures may be a range rather than a specific temperature

Transition temperatures Specific volume Liquid Rubbery Amorphous/ glassy Crystalline solid Temperature Tg Tm

Condensation polymers XOH + HY  XY + H2O HOXOH + HYH  HOXYH + H2O further reactions with HOXOH and HYH will produce a linear molecule

Condensation polymers Acid + base  salt + water HCl + NaOH  NaCl + H2O Acid + alcohol  ester + water R.C=O.OH + HO.R’  R.C=O.O.R’ + H2O Acid + amine  amide + water 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 +H2O further reactions with HOXOH and HYH will produce a linear molecule HOXH + HOXH  HOXXH +H2O i.e. both reactants might be on one molecule but such a system could react with itself to form a cyclic molecule if X > 4C atoms such a cyclic molecule can polymerise without loss of water (H2O already removed in cyclisation reaction)

Ring-opening polymers Ring-opening polymerisation during composite manufacture has potential to produce thermoplastic matrix composites from RTM/RIFT caprolactam to produce polyamide 6 (e.g. DSM Fiber Intermediates APA-6), laurolactam to produce polyamide 12 (e.g. EMS-Grivory APLC12), and cyclic butylene terephthalate oligomers to produce PBT polyester (e.g. Cyclics Corporation).

Voluntary Plastic Container Coding System abc 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.....

LDPE 4 -130 +105 HDPE 2 -125 +135 PP 5 PA6,6 7 +55 +255 PVC (V) 3 -- Polymer Acronym Coding Tg (ºC) Tm (ºC) Morphlgy Low-density polyethylene LDPE 4 -130 +105 crystalline High-density polyethylene HDPE 2 -125 +135 Polypropylene PP 5 -27 .. -10 +165 .. +170 Polyamide (nylon) 6,6 PA6,6 7 +55 +255 Poly vinylchloride PVC (V) 3 +75 .. +80 -- amorphous Polystyrene PS 6 +90 .. +100 Polyethylene terephthalate PET (PETE) 1 +67 .. +80 265 Polycarbonate PC +145 .. +150 Polyoxymethylene (acetal) POM < -150 +180 Polyurethane PU +140 Poly ether ether ketone PEEK +144 367

Periodic Table of Thermoplastics (Tangram Technology) http://polymer

Summary of thermoplastics lecture basic chemical names addition polymers configuration/conformation stereoregularity/tacticity crystalline or amorphous transition temperatures condensation polymers ring-opening polymers

MATS117 continues with thermosetting polymers….

Thermosets generally supplied as a liquid cross-linked (cured) by chemicals (and heat) heat increases the rate of cure heat reduces the instantaneous viscosity cure decreases the viscosity over time product is a 3D molecular network whereas a thermoplastic is usually a 2D chain

Summary (key polymers) Polymern Curing Properties Ph-F Condensation Low-cost, brittle, FST Epoxy Ring-opening High-cost, High-performance UPE Addition Intermediate cost Balanced performance