2. Polymer Processing

6. Polymer materials Primary Bond - Covalent Bonding Primary Bond - Covalent Bonding Secondary Bonds – Secondary Bonds – van der Waals van der Waals Dipole Bonds Dipole Bonds Hydrogen Bonds Hydrogen Bonds H C H PE - mer

7. Polymer Properties T g T g Glass Transition Temperature Glass Transition Temperature MW MW Molecular Weight Molecular Weight The combination of these two properties will be a great starting point for identifying any polymer material The combination of these two properties will be a great starting point for identifying any polymer material

8.  Reinforcing fibers  Boron, carbon, fibrous minerals, glass, Kevlar  Increases tensile strength. Increases flexural modulus. Increases heat-deflection temperature (HDT). Resists shrinkage and warpage.  Conductive fillers  Aluminum powders, carbon fiber, graphite  Improves electrical and thermal conductivity.  Coupling agents  Silanes, titanates  Improves interface bonding between polymer matrix and the fibers.  Flame retardants  Chlorine, bromine, phosphorous, metallic salts  Reduces the occurrence and spread of combustion.  Extender fillers  Calcium carbonate, silica, clay  Reduces material cost.  Plasticizers  Monomeric liquids, low- molecular-weight materials  Improves melt flow properties. Enhances flexibility.  Colorants (pigments and dyes)  Metal oxides, chromates, carbon blacks  Provides colorfastness. Protects from thermal and UV degradation (with carbon blacks).  Blowing agents  Gas, azo compounds, hydrazine derivatives  Generates a cellular form to obtain a low- density material.

9. Major Processes Extrusion Extrusion Injection Molding Injection Molding Blow Molding Blow Molding Thermoforming Thermoforming Rotomolding Rotomolding

10. Polymer Processes

11. Extrusion

12. Extrusion Product Examples

13. Extrusion The extrusion machine forms the basis of nearly all other polymer processes. The extrusion machine forms the basis of nearly all other polymer processes. Basically involves melting polymer pellets and extruding them out through a two dimensional die. Basically involves melting polymer pellets and extruding them out through a two dimensional die. Produces long, thin products Produces long, thin products Coating for electrical wire Coating for electrical wire Fishing Line Fishing Line Tubes, etc. Tubes, etc.

14. Injection Molding

15. Injection Molding Product Examples Nylon sheaves

16. Injection Molding Machine Basics

17. Injection Molding Machine Operating Sequence The cavity fills as the screw moves forward as a plunger The cavity fills as the screw moves forward as a plunger The cavity is packed as the screw continues to move forward as part solidifies The cavity is packed as the screw continues to move forward as part solidifies Mold closes and screw begins moving forward for injection Mold closes and screw begins moving forward for injection

18. Injection Molding Machine Operating Sequence, ctd The cavity cools as the gate freezes off and the screw begins to retract to plasticize material for the next shot The cavity cools as the gate freezes off and the screw begins to retract to plasticize material for the next shot The mold opens for part ejection The mold opens for part ejection The mold closes and the next cycle begins The mold closes and the next cycle begins

19. Injection Molding Process Control Very similar to die casting Very similar to die casting Must control heat transfer and fluid flow Must control heat transfer and fluid flow Do that by controlling temperature and pressure Do that by controlling temperature and pressure

20. Co-injection Molding 1. Inject Skin 2.a. Inject Core 2.b. Continue injecting core until cavity is filled 3. Inject Skin again to purge sprue.

21. Injecting hollow parts with complex interior geometry

22. Gas Assist Injection Molding – Hollow parts without interior control

23. Injection – Compression Molding  Very similar to squeeze casting

24. Injection Molding of Thermosets Thermoplastics “set” when they cool Thermoplastics “set” when they cool Mold temperature will be set to allow full cavity fill, while increasing production rate Mold temperature will be set to allow full cavity fill, while increasing production rate Thermosets undergo a chemical crosslinking that produces the solid structure Thermosets undergo a chemical crosslinking that produces the solid structure Mold temperature will be hotter usually – set to allow full cavity fill, while accelerating the chemical reaction to cure. Mold temperature will be hotter usually – set to allow full cavity fill, while accelerating the chemical reaction to cure. Often called “Reaction Injection Molding” (RIM) Often called “Reaction Injection Molding” (RIM)

25. Blow Molding

26. Injection Blow Molding Extrusion Blow Molding Stretch (Parasin) Blow Molding

27. Blow Molding Cost Analysis 500 ml bottle – using a preform Cost per bottle 500 ml bottle – direct form mfg Cost per bottle Preform$0.040Bottle$0.12 Shipping (500,000 per container @ $3000 per 40') $0.006 Shipping (50,000 per container @ $3000 per 40’) $0.06 Labor ($12 per hour) $0.004 Waste (5%) $0.002 Electricity ($0.20 per Kwh) $0.004 TOTAL$0.056TOTAL$0.18

28. Thermoforming

29. Thermoforming Products

30. Thermoforming

31. Thermoforming Video

32. Rotomolding

33. Rotomolding Used for relatively dimensionally inaccurate items, usually with a hollow interior Used for relatively dimensionally inaccurate items, usually with a hollow interior Can be very large Can be very large Garbage Cans Garbage Cans Kayaks Kayaks Interior dimensions can not be critical Interior dimensions can not be critical Relatively primitive and therefore inexpensive process Relatively primitive and therefore inexpensive process

34. Polymer Recycling 1998 – Approximately 20% of plastic waste is recycled (optimistic estimate) 1998 – Approximately 20% of plastic waste is recycled (optimistic estimate) 1998 – Polymers account for approximately 18% by volume of material to landfills 1998 – Polymers account for approximately 18% by volume of material to landfills

35. Needs vs Challenges Needs for a viable program: Needs for a viable program: Stable supply of materials with reliable collection and sorting Stable supply of materials with reliable collection and sorting Economical, proven and environmentally sound recycling process Economical, proven and environmentally sound recycling process End use applications for the recycled material End use applications for the recycled material Challenges Challenges 10-12 main polymer types Thousands of blends Additives Impurities in supply (labels, glass, dirt, etc)

36. Recycling of Polymers PET (polyethylene terphthalate) beverage containers, boil-in food pouches, processed meat packages HDPE (high density polyethylene) milk bottles, detergent bottles, oil bottles, toys, plastic bags PVC (polyvinyl chloride) food wrap, vegetable oil bottles, blister packaging LDPE (low density polyethylene) shrink-wrap, plastic bags, garment bags PP (polypropylene) margarine and yogurt containers, caps for containers, wrapping to replace cellophane PS (polystyrene) egg cartons, fast food trays, disposable plastic silverware Other multi-resin containers

37. Basic recycling steps Sorting Sorting Size Reduction Size Reduction Densification Densification Pulverization Pulverization Melt Filtration Melt Filtration

38. Sorting Manual – very common Manual – very common Density based sorter Density based sorter Centrifugal Centrifugal Float/Sink methods Float/Sink methods Optical – same as peas, potato chips, etc Optical – same as peas, potato chips, etc Spectroscopy – Infrared – automation possible Spectroscopy – Infrared – automation possible

39. Size Reduction Shredders Shredders Rotary Knife Rotary Knife

40. Densification Basic purpose is to reduce to volume taken up by bulk material Basic purpose is to reduce to volume taken up by bulk material Reduce from only 20 kg/m 3 to almost 400 kg/m 3 Reduce from only 20 kg/m 3 to almost 400 kg/m 3 Agglomeration – heat it up and compact it Agglomeration – heat it up and compact it

41. Pulverization Convert clean plastic waste into powder Convert clean plastic waste into powder After this process, some of the product can actually be used if low purity requirements After this process, some of the product can actually be used if low purity requirements Recycled plastic lumber for example Recycled plastic lumber for example

42. Melt Filtration Improve purity of pulverized polymer Improve purity of pulverized polymer Needed for extrusion, injection or blow molding processes Needed for extrusion, injection or blow molding processes Basic process concept: Basic process concept: Melt it Melt it Shove it through a screen Shove it through a screen Additional chemical processing may be needed if additional purity requirement Additional chemical processing may be needed if additional purity requirement