1. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 1 Bruce Mayer, PE Engineering-45: Materials of Engineering Bruce Mayer, PE Licensed Electrical & Mechanical Engineer BMayer@ChabotCollege.edu Engineering 45 Polymer Structures

2. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 2 Bruce Mayer, PE Engineering-45: Materials of Engineering Learning Goals – Polymer Structure  Learn The Basic Electronic Structure of Very Long Organic Molecules  Understand Basic MicroStructural Features of Polymers  Calculate Molecular Weights for Long- Chain Polymers  Learn the Difference between ThermoSETTING and ThermoPLASTIC Polymers

3. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 3 Bruce Mayer, PE Engineering-45: Materials of Engineering Ancient Polymer History  Originally natural polymers were used Wood, Cotton, Leather, Rubber, Wool, Silk  Early Human-History Uses for the Natural PolyMers Rubber balls used by Incas Noah used pitch (a natural polymer) for Sealing the Ark

4. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 4 Bruce Mayer, PE Engineering-45: Materials of Engineering Organic Chemistry  Recall PolyMer  Many Mers  Mer  a Single Chemical Unit  Almost All Solid Polymer Materials are “Organic” in Nature  Organic → Based on CARBON  Almost All Organic Chemicals are a combination of Carbon And HYDROGEN

5. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 5 Bruce Mayer, PE Engineering-45: Materials of Engineering C-H Bond  ReCall from Periodic Table the Valences for C & H C → Grp IVa → 4 Valence e − H → Grp 1A → 1 Valence e −  Thus in a C-H molecule Both can Attain the Noble-Gas Configuration if 4 H’s Give their e − ’s to 1 Accepting C  Four-H’s and 1-C Yield the METHANE molecule

6. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 6 Bruce Mayer, PE Engineering-45: Materials of Engineering Single, Double, Triple Bonding  First Note That the Methane Molecule is NOT Planer in 3D As Might be Expected the H’s Take Equal Separation to Form a Tetrahedral Structure  In Methane, Each H Atom Shares ONE e − This Configuration is Shown Schematically as Each C-H is connected by a SINGLE Bond as depicted the Single-Line Connection

7. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 7 Bruce Mayer, PE Engineering-45: Materials of Engineering 1X, 2X, 3X Bonding cont.1  Another Electronic Configuration, Ethylene, Has the two adjacent Carbons sharing TWO e − to achieve the Neon Configuration  In this case the C=C connection is termed a DOUBLE Bond  Similarly, in Acetylene two Carbons Share 3 e − to form a TRIPLE Bond

8. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 8 Bruce Mayer, PE Engineering-45: Materials of Engineering The C-H Chain Basic-Mer  Consider the Base Methane Molecule with the end-H’s Removed  The CH 2 Fragment, or Mer, can Repeat Almost endlessly, creating very large PolyMer Chain Molecules  There can be Many basic Mers consisting of 2X or 3X bonded C’s Other Atoms, or Ions (Molecule Fragments) may Substitute for H  The Central Carbon Can Connect to Similar Fragments with a 1X Bond to form a CHAIN

9. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 9 Bruce Mayer, PE Engineering-45: Materials of Engineering PolyMer MicroStructure  Some Typical Repeating-Mer (PolyMer) Structures  C-C Forms a Very Strong intRAmolecular Bond The CoValent IntERmolecular Bond Strength Varies with the Form of the Chain-to-Chain Electronic interaction Direction of increasing strength

10. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 10 Bruce Mayer, PE Engineering-45: Materials of Engineering Mer Forms in 3D PE: polyethylene Phenol-formaldehyde (Bakelite) PVC: polyvinyl chloride PET: polyethylene terephthalate (a polyester)

11. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 11 Bruce Mayer, PE Engineering-45: Materials of Engineering Example → PolyEthylene  Poly (many) Mer (parts): A large molecule made up of one or more repeating units (mers) linked together by covalent chemical bonds.  The PolyEthylene Chemical Reaction n = number of monomers reacting >> 1

12. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 12 Bruce Mayer, PE Engineering-45: Materials of Engineering Effect of Molecular Weight on the Properties of PolyEthylene

13. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 13 Bruce Mayer, PE Engineering-45: Materials of Engineering PolyMer Chemistry  Polymer MACROmolecules Produce NONcrystalline Solids by the interMolecular Bonding  The Chain-Creating “PolyMerization” Chemical Reaction usually Proceeds with the aid of a catalyst, R monomers + catalyst (initiator) = polymer chain Poly Ethylene polyethylene (C 2 H 4 Mer) C H

14. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 14 Bruce Mayer, PE Engineering-45: Materials of Engineering Molecular Geometry  As indicated in the Previous Slide Any Three Carbons in the “BackBone” form Something near the Classic Tetrahedral Angle (109.471°)  However the Molecules are NOT constrained to TWO Dimensions  The BackBones can Rotate, Kink, or Coil to Generate Randomly Complex Shapes

15. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 15 Bruce Mayer, PE Engineering-45: Materials of Engineering Isomerism  IsoMerism  two compounds with same chemical formula can have quite different structures Example: C 8 H 18 –n Octane –2-methyl-4-ethyl pentane (IsoOctane)

16. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 16 Bruce Mayer, PE Engineering-45: Materials of Engineering Cross-linking  Generally, amorphous polymers are weak.  Cross-linking adds strength: vulcanized rubber is polyisoprene with sulphur-based cross-links:

17. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 17 Bruce Mayer, PE Engineering-45: Materials of Engineering PolyMer Size Characterization  MOLECULAR WEIGHT, M w  Mass of a mol of chain-molecules  Average CHAIN SIZE, n  Number of Mers per Chain Also Called the “Degree of PolyMerization”  Some Consequences: M w ↑  T melt ↑ short chains (~100 g/mol): liquid or gas long chains (1000 g/mol): waxy solid, soft resin “high polymer” (>10,000 g/mol): solid  Also M w ↑  TS↑ Longer chains are entangled (anchored) better

18. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 18 Bruce Mayer, PE Engineering-45: Materials of Engineering MOLECULAR WEIGHT M w is more sensitive to higher molecular weights Molecular weight, M i : Mass of a mole of chains. Lower M higher M

19. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 19 Bruce Mayer, PE Engineering-45: Materials of Engineering Molecular Weight Calculation  Example: average mass of a class Σ=10Σ=1860

20. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 20 Bruce Mayer, PE Engineering-45: Materials of Engineering Tacticity  isotactic – all R groups on same side of chain  syndiotactic – R groups alternate sides  atactic – R groups random

21. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 21 Bruce Mayer, PE Engineering-45: Materials of Engineering Cis/Trans IsoMerism cis Form cis-isoprene (natural rubber)  Bulky groups on same side of chain trans Form trans-isoprene (gutta percha)  bulky groups on opposite sides of chain

22. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 22 Bruce Mayer, PE Engineering-45: Materials of Engineering CoPolyMers  Two or More MonoMers PolyMerized ToGether random block graft Adapted from Fig. 14.9, Callister 7e. alternating A B random – A and B randomly vary in chain alternating – A and B alternate in polymer chain block – large blocks of A alternate with large blocks of B graft – chains of B grafted on to A backbone

23. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 23 Bruce Mayer, PE Engineering-45: Materials of Engineering PolyMer Crystallinity  % Crystalinity  % of Material that is crystalline  TS and E often increase with % crystallinity  Annealing causes crystalline regions to grow. % crystallinity increases Simulated conformation of a polymer chain consisting of 100 main chain repeat units and 50 side chains, each consisting of 20 repeat units.

24. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 24 Bruce Mayer, PE Engineering-45: Materials of Engineering PolyMer Xtals - Spherulites  Polymer Single Xtals Often Form Plate-like, or Lamellar, Structures by Folding Back on themselves  In Bulk Material, Amorphous regions of Twisted & Kinked “Tie Molecules:”connect the Lamellae Lamellae Tie Molecules  Upon Heating the Layered Structures Become Spherical with an “Onion- Layer”, or Spherulitic, Structure

25. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 25 Bruce Mayer, PE Engineering-45: Materials of Engineering Polymer-ChainStructure v. Heating ThermoPlastic ThermoSetting

26. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 26 Bruce Mayer, PE Engineering-45: Materials of Engineering ThermoPlastic Polymers  Polymers which melt and solidify withOUT chemical change are called thermoplastics.  They support hot-forming methods such as injection-molding

27. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 27 Bruce Mayer, PE Engineering-45: Materials of Engineering ThermoSet Polymers  Polymers which irreversibly change when heated are called thermosets.  Most often, the change involves cross-linking which strengthens the polymer (setting).  Thermosets will not melt, and have good heat resistance.  They are often made from multi-part compounds and formed before setting (e.g. epoxy resin)  Setting accelerates with heat or, for some polymers, with UV light.

28. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 28 Bruce Mayer, PE Engineering-45: Materials of Engineering ThermoSets vs ThermoPlastics  ThermoPlastics little cross linking ductile Soften, then Melt with heating Examples –polyethylene (PE) –Polypropylene (PP) –Polycarbonate (Lexan) –polystyrene (StyroFoam)  ThermoSets large cross linking –10 to 50% of mers hard and brittle do NOT soften with heating –Decompose Instead Examples: vulcanized rubber, epoxies, polyester resin, phenolic resin 1 st Synthetic Polymer

29. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 29 Bruce Mayer, PE Engineering-45: Materials of Engineering WhiteBoard Work  Prob 14.9 For the Kinked & Twisted Polymer at right Find –Total Length, L –End-to-End distance, r Given –Eqns 14.11 & 14.12 –M n for Linear PolyPro = 300 kg/mol Simulated conformation of a polymer chain consisting of 100 main chain repeat units and 50 side chains, each consisting of 20 repeat units.

30. BMayer@ChabotCollege.edu ENGR-45_Lec-29_PolyMer_Structures.ppt 30 Bruce Mayer, PE Engineering-45: Materials of Engineering Appendix - BakeLite  The First Synthetic Polymer  Invented by Leo Beakeland (1863 - 1944) in 1907 in Yonkers, NY  Chemical Name → phenol formaldehyde (Phenolic)  Historic Products 1912 - A Bakelite record invented by Edison. (USA) 1912 - Bakelite billiard balls invented by Hyat Burroughs. (UK) 1914 - The telephone receiver made of Bakelite by Western Electric. (USA) 1915 - Photo camera from Kodak by Eastman gets a Bakelite case. (USA) 1923 - Philips radio company starts with its own Bakelite production, called Philite. (Netherlands) 1926 - First Bakelite chair 1927 - First Philite radio speaker made by Philips. (Netherlands) –See also  http://www.mbzponton.org/valueadded/maintenance/bakelitehist.htm