Thermoplastic polymers processed by a heat-form-cool cycle

1. Thermoplastic polymersprocessed by a heat-form-cool cycle John Summerscales

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

3. Naming basic chemicals

4. Basic chemicals Transition temperature data from http://www.elmhurst.edu/~chm/vchembook/501hcboilingpts.html

5. Rotation about a single bond • Orange and yellow are larger atoms

6. Rotation about a single bond • Orange and yellow are larger atoms

7. Rotation about a single bond • Orange and yellow are larger atoms

8. Rotation about a single bond • Orange and yellow are larger atoms

9. Rotation about a single bond • Orange and yellow are larger atoms

10. Rotation about a single bond • Orange and yellow are larger atoms

11. Geometric isomers • cis: • trans:

12. 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 ismacromolecules only 1 repeating unit homopolymer 2 different repeating units copolymer 3 different repeating units terpolymer

13. Polymers • thermoplastic - usually long straight chainssometimes with short branches • copolymers AB (or terpolymers ABC) can be • alternating ---ABABABABAB--- • block ---AAABBAAABB--- • graft (type B branches on type A backbone) • random ---AABABBBAAB--- • thermoset - usually 3-dimensional networks • elastomer - 3-D networks with sparseinterlinks between chains (e.g. rubber)

14. 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

15. Configuration/Conformation • Configuration • 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 crystallisebut more likely to be amorphous

16. Stereoregularity -> tacticity • Isotactic • characteristic groupsall on the same sideof the polymer chain • Syndiotactic • characteristic groupson alternate sidesalong polymer chain • Atactic - characteristic groups located atrandom along the polymer chain • images from http://plc.cwru.edu/tutorial/enhanced/files/polymers/struct/Struct.htm

17. 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)

18. 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

19. 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 rangerather than a specific temperature

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

21. Chemical Groups (reactants) O H C O HO H N H • Acid • Alcohol • Amine nitrogen in amine has a free p-orbitalwhich can become part of a π-bond

22. Chemical Groups (products) O C O O O C N H • Ester • Amide • Ether

23. Condensation polymers • XOH + HY  XY + H2O • HOXOH + HYH  HOXYH + H2O • further reactions with HOXOH and HYHwill produce a linear molecule

24. 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

25. Ring-opening polymers • HOXOH + HYH  HOXYH +H2O • further reactions with HOXOH and HYHwill produce a linear molecule • HOXH + HOXH HOXXH +H2O • i.e. both reactants might be on one molecule • if X > 4C atoms,system reacts with itself to form a cyclic molecule • such a cyclic molecule can thenpolymerise without loss of water(H2O already removed in cyclisation reaction)

26. Ring-opening polymers • ring-opening polymerisationduring composite manufacturecan produce thermoplastic matrix composites by RTM or 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).

27. Voluntary Plastic Container Coding System abc n • proposed by Society for the Plastics Industry (SPI) in the United States of America • black plastic packaging, coloured using carbon black pigments, cannot be easily identified by the optical/near-infrared (NIR) sorting systems. • remember Tm = Tg + 200°C (±~50°C) so some common thermoplastics are.....

29. Periodic Table of Thermoplastics(Tangram Technology)http://www.tangram.co.uk/TI-Polymer-Periodic%20Table.pdf

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