1. Polymer Processing 1

2. 2 Processing Method –Choice is dictated by the product desired and the quantity desired. Fiber, film, sheet, tube Cup, bucket, car bumper, chair. –Fiber manufacture is different, it is continuous. –Large quantities usually use extrusion or injection molding –Smaller quantities use compression molding or transfer molding

3. Processes for Thermoplastics: Extrusion Blow Molding Injection Molding Thermoforming Calendaring Spinning Forming Processes for Thermosetting polymers: Compression Molding Transfer Molding 3

4. Thermoplastic: the resin is heated to make a viscous liquid and then processed into a usable object without much additional chemistry. Example: polyethylene, polystyrene. Thermoset: upon heating, further reaction occurs to make molecules “set up” into a useful product. Chemistry occurs, so these are sometimes called “reactive polymers”. The resin may be provided as either small molecules or “prepregs”— partially polymerized stuff. Example: polyurethanes, phenol- formaldehyde, melamine-formaldehyde, epoxy glue. 4

5. Compression Molding Platen Mold Plunger Guide Pins Mold Cavity Platen Hydraulic Plunger Heat and Cooling Hydraulic Pressure Compound to be molded 5

6. Injection Molding Hydraulic Pressure Nozzle Feed hopper, contains polymer pellets 6

7. 7 Polymer is heated, mixed, the then forced to flow into a mold cavity Similar to extrusion –Hopper, barrel, screw Screw rotation is the principal motion only in one part of the cycle –Mixes, compacts, plasticizes, and heats

8. 8 In the injecting stage, the screw is driven axially by a piston to generate the working pressure –150 – 250 MPa (21,756 – 36,260 psi)

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10. 10 Injection Molding Sequences (1) Close the mold (2) Inject the melt (3) Retract the screw(4) Open mold – eject part

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12. 12 Two Plate Mold The mold here is closed The mold is position between two platens –One stationary –One moveable Note the water channels for quickly cooling the mold and its polymer load. Sprue: channel from die nozzle Into the mold Runner: channel from Sprue Into the cavity Gates: restrict the polymer Flow into the cavity

13. 13 Two Plate Mold 2 The mold here is open The ejector pins push the rather fragile plastic from the mold cavity The sprue and runners are waste..

14. Blow Molding—e.g. milk bottle Extruded Parison- Mold Open Mold Closed and Bottle Blown Finished Bottle Removed from Mold Pl astic 14

15. Four-roll calender Wad of plastic To conditioning equipment 15

16. 16 Extrusion This process is fundamental to both metals and ceramics as well as polymers. Definition –Extrusion is a compression process Material is forced to flow through a die orifice Cross-sectional shape determined by the shape of the orifice Product is long and continuous

17. A Plastics Extruder Feed hopper Heaters Cores for cooling water Die Screw Drive shaft 17

18. 18 Rarely used for thermosetting polymers Products Tubing, pipes, and hose Window and door moldings Sheet and film Continuous filaments (as we saw in module 3A) Coated electrical wire and cable.

19. 19 The extruder consists basically of – a hopper and –a barrel and –a screw.

20. Fiber Drawing Drive roll Heater (Optional) Drawn yarn to bobbin Undrawn pretwisted yarn Control rolls Snubbing pin Skewed idler roll 1 2 ( 2 > 1 ) Stretching Zone 20

21. Dry Spinning: From solution Melt Spinning: From Melt Nylon 6,6 & PETE Cellulose Acetate Wet Spinning: From solution into solution Kevlar, rayon, acrylics, Aramids, spandex 21

22. Melt Spinner Bobbin Extruded Fiber Cools and Solidifies Here Metered Extrusion (controlled flow) Melting Zone Polymer Chips/Beads Pump Filter and Spinneret Air Diffuser Heating Grid Pool Lubrication by oil disk and trough Packaging Bobbin drive Yarn driver Feed rolls Moisture Conditioning Steam Chamber 22

23. Melt spinning 23

24. Dry Spinning of Fibers from a Solution 24

25. Wet Spinning (e.g. Kevlar) 25

26. Thermoforming Three major types of thermoforming –Vacuum Pressure limit of 1 atmosphere –Pressure Higher allowable pressures –Mechanical 26

27. Vacuum Thermoforming 27

28. Pressure Thermoforming 28

29. Mechanical Thermoforming In (1) the polymer is pre stretched In (2) the polymer is draped over the positive mold and pressure applied to force it in place 29

30. Mechanical Thermoforming In (1) the polymer is pre heated In (2) the polymer is forced into place in the negative mold. 30