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The beauty and nightmare of plastics, bath university 2019

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This presentation was given at Bath University in March 2019 and it describes the beauty of science relating to plastics and the problems associated with certain application areas of the material

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The beauty and nightmare of plastics, bath university 2019

  1. 1. The Beauty and Nightmare of Plastics By Malcolm Mackley, Emeritus Professor, Department of Chemical Engineering and Biotechnology University of Cambridge 1 Polyethylene “single crystals” “Plastic Free Kingsbridge” Bath University. March 2019
  2. 2. 2 Several messages in the talk. • The “beautiful” science and engineering in plastics. • How “beautiful science” can result in problematic global technology. • The “problem with plastics”. • The beauty and nightmare of; …(many Science to Global Technologies).
  3. 3. 3 1947 1957 1967 1977 1987 1997 2007 2017 Ipswich Suffolk Gravesend, Kent Gravesend Technical SchoolBath Technical CollegeLeicester Univ Leicester Univ Bristol University Sussex UnivCambridge University Cambridge University Cambridge University Cambridge University Salcombe, Devon My own “brief history” time line.
  4. 4. Plastics are Polymers! The plastic polyethylene (PE) is the world largest commodity thermoplastic. 4
  5. 5. “Polymers (including plastics!) are beautiful and fantastic” DNA, the stuff of life Polyethylene (PE), a “man made polymer” 1934 discovery 5 Cellulose, one of natures building blocks
  6. 6. Polyethylene (PE) has an incredible molecular structure. Graphic courtesy of Alexi Likhtman, University of Reading Total Chaos Perfect Order Random Coil, in the melt or rubbery solid Perfect Crystal, in fibre or tape 6
  7. 7. 7 Rubbery or MoltenTough and Strong solid PE has a very wide range of mechanical properties Macro. mm-m Micro. mm Nano. nm Molecular. Angstrom Semi crystalline solid Diamond like Perfect order Total chaos
  8. 8. 8 Polyethylene Molecular and Nanostructure. (My Bristol Physics PhD Supervisors 1970s) Sir Charles Frank (1911-1998)Andrew Keller (1925 –1999)
  9. 9. 9 “Beautiful” Polyethylene Crystal “Nanostructures” Bristol Physics 1950-1970s PE “single crystals” PE “shish kebabs” nanofibres PE micro “Spherulites” 10 mm 10 nm
  10. 10. 10 Polyethylene Unit cell Diamond If PE chain fully aligned in crystal. Expect PE Stiffness E=285 GPa Not usual E=1 GPa Frank 1970 C.W.Bunn 1945 Sir Charles Frank prediction; High Modulus Polyethylene 1970s Towards Global Problems ! Step 1. Great Science; an example, High Modulus PE
  11. 11. 11 Step 2. The Technology; to produce High Modulus PE Low Entanglement, Ultra High Molecular Weight (UHMWPE) Gel Drawing 1980 Piet Lemstra TU Eindhoven Low entanglement UHMWPE polymer gel. 1% polymer in solvent Unoriented Gel fibre Quench bath Unoriented Low entanglement semi crystalline fibre . Hot draw Oriented High Modulus 100 GPa Polyethylene Solvent recovery Piston Ex Groningen Ex Bristol Paul Smith. ETH
  12. 12. 12 Step 3. Commercialisation. Continuous Processing of DSM UHMWPE Dyneema fibre. late 1980s Screw extruder UHMWPE Polymer powder Solvent Low entanglement polymer gel Spinneret Gel fibres Quench bath Low entanglement semi crystalline fibre Hot draw Solvent recovery High Modulus Polyethylene Han Meijer. DSM & Eindhoven
  13. 13. 13 1. Science. Then….. 2. Technology. Then….. 3. Commercialisation. Then sometimes… 4. Global scale up. Then…. 5. A problem? Dyneema ropesDyneema and Endumax Body armour Endumax Bomb protection Step 4. Global Scale up. High Modulus PE 1990- 2019 Endumax sails
  14. 14. 14 Polyethylene (PE) Global manufacture. 1934-2019 Globally, 2018 > 100 million tonnes/annum = Fill Salcombe Estuary / annum with PE
  15. 15. 15 Westbury Wilts Cement Works 1960- 2010 (Where my father was Production Manager 1962- 1980) 700,000 tonnes cement/annum. 35 million tonnes of cement over 50 years. 25 million tonnes of chalk. Global PE 100 million tonnes/annum; enough to fill the chalk quarry at least 4 times over/annum. (Wiltshire Times) Drone Photo Simon Wright ‘Skynamite’
  16. 16. 16 Temperature 50 100 150 200 C0 DH Melt Processing The “good” and “bad” properties of PE • Low melting point. • Low density. • High strength and toughness. • “Low cost?”. • Ease of processing. Polyethylene £ 1000/tonne (Paper £ 300 /tonne) • Relatively poor gas diffusion barrier. Plastic floats! Good for low temp processing. Bad for flammability. Bad for some food packaging applications
  17. 17. 17 Ease of melt Processing ; a reason why plastic is used so much. 1 10 100 1000 10000 1 10 100 1000 10000 100000 1000000 S7 S8 S9 S10 S11 S12 Apparent Viscosity Pas Entanglement of chains Shear Thinning Simulation. Experiment. Birefringence stress fields Stress field birefringence Cambridge Multipass Rheometer (MPR) (David Hassell) Strain rate Video of Flow birefringce within slit. To view, go to; http://www.malcolmmackley.com/discovery-and-innovation/movies/
  18. 18. 18 Thirty years of research results for example in the ability to mathematically model and optimise plastic bottle blow moulding. Whilst at the same time…Thirty years is enough time to create a global plastic bottle nightmare. Plastic Bottles ! UK; 35 million plastic bottles /day
  19. 19. 19 PE Applications Sustainably “benign” Tube and pipe extrusion. Injection moulding.
  20. 20. 20 Plastic packaging and bottles are a Global problem PE application; Film blowing and blow moulding
  21. 21. 21 “The birth” of single use plastic drinking cups? Street Scenes whilst at a food conference in San Antonio USA 2007 Photos used in my 2008-2011 Rheology lectures suggesting this would become a common sight in the UK too! Single use plastics; in the beginning?
  22. 22. 22 2017. The World finally realised; “We have a problem.” “The Plastic Bashers” In the UK, recognition of problem, Surfers Against Sewage (SAS). Micro plastics in oceans. Beach cleaning groups. BBC Blue Planet programme. China stopped accepting recycled plastic waste. 2018. local and National Politicians start to get involved. National, European and Global policies starting to emerge. 2019. ? The trouble with plastics
  23. 23. 23 This is a very well written 2018 Government paper which has excellent ideas that are unlikely to be acted on?
  24. 24. 24 The Solutions! • Collect separated used plastic. • Recycle. • Burn. • Burn and recover energy. • Go biodegradable. • Restrict application areas for plastics. • Tax manufacturers, processors, distributors, users. • Penalise inappropriate users of plastics. • Educate populous to use plastics sensibly.
  25. 25. 25 The Bright side of Plastics. The Dark side of Plastics. A “man made” organic material that has very effective mechanical and electrical properties. Some applications have current environmental problems; however Governments and users now realise these problems; but in “poorer countries” remedial action has not been taken. Some plastics manufacturers and processors are still in denial in terms of genuine sustainability and using plastics to “make the world a better place”.
  26. 26. 26 Plastics are not alone ! Other technologies with global problems. • Minerals. Mining toxic tailings (waste pits) • Mobile phones. 1 Billion/annum. Materials recycle, Society and social aspects. • CO2 Global warming • Transportation. • Mathematics! • The internet of things. • Drones. • ………………. Burst tailings dam. Brazil Jan 2019
  27. 27. 27 Wise words! Peter Swinnerton Dyer (1927-2019) ex Cambridge Vice Chancellor “You can never observe Cambridge changing. You can only observe that it has changed.” We now know, fast developing Science and Global Technologies, including plastics can have both a positive and negative effect on society. Hopefully current and future generations will recognise this and ensure a balanced approach to current and future technology changes. Sustainable Innovation and design.

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