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Very few readers of this issue can remember, or even imagine, what it was like when an injection molding machine did not have a screw, but only a smooth-bore plunger. Very few can remember a time when there were no twin-screw extruders; no multi-layer film, sheet, or bottles; no accumulator-head or injection blow molders; no polypropylene, HDPE, or polycarbonate; and no such thing as RIM or rotomolding or structural foam—or even a melt indexer. How and when these technologies got started are just some of the little-known stories that are told in the following pages. Fifty stories, in fact—one for each year this magazine has been reporting on the latest ways to manufacture with plastics.

So many essential technologies surfaced in the last half-century that it was perplexingly difficult to select just 50 to celebrate here. We invited long-time industry experts in all areas of plastics to help us make those choices. Turn the page to see who they are.

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Even with the help of nearly 2000 years of collective plastics experience, our editors had to make some tough calls. For example, we ruled out microprocessor controls because the computer revolution has had a universal impact, and plastics rode the wave along with every other industry. Likewise, we left out printing and decorating technologies because they had prior history with other materials. We also had to skip worthy candidates in some fields so as to broaden our coverage to all areas of plastics. Please note that we have not presented these 50 innovations in any particular order, except for the first four, which did pull the most votes.

Some readers may disagree with our choices, and some may argue over who deserves pioneering credit in a particular field. Our editors found it much harder than expected to retrace the history of these 50 innovations. So few eyewitnesses to this history are still accessible for interviews. Relatively little has been published on this field of technological history. And many records were lost or discarded in the myriad corporate mergers over the decades. So we often had to rely on individuals’ memories of past decades. And we had to resolve inevitable disagreements over some dates and facts.

You’ll see that it was worth it. These are important stories. They reveal the origins of so much that we take for granted—in brilliant intuition, hard work, or plain good luck.

Top 50 Innovations

1. Reciprocating Screw Injection
2. Polypropylene
3. HDPE
4. Polycarbonate
5. Twin-Screw Extrusion
6. LLDPE
7. Sheet Molding Compound
8. Ultrasonic Welding
9. Stretch-Blow Molding
10. Desiccant Dryers
11. ABS Resins
12. Parison Programming
13. Structural Foam
14. Barrier Screws
15. Accumulator-Head Blow Molding
16. Super-High-Heat Thermoplastics
17. Melt Indexers
18. Carbon Fiber
19. Injection Molding Simulation
20. Thermoplastic Elastomers
21. Hot Runners
22. Takeout Robots
23. Pressure Forming
24. Rotary Thermoforming
25. Halogenated Flame Retardants
26. PET and PBT
27. Film/Sheet Coextrusion
28. Multi-Material Injection
29. Multi-Layer Blow Molding
30. Hindered Phenolic Antioxidants
31. HALS UV Stabilizers
32. All-Electric Injection Presses
33. Rotational Molding
34. Gas-Assist Molding
35. In-Mold Decorating & Labeling
36. Cavity-Pressure Sensing
37. Spray-Up Composites
38. Injection Blow Molding
39. Pur Thermal Insulation
40. RIM
41. Foam Extrusion
42. Underwater Pelletizing
43. Chemical Blowing Agents
44. Spiral Dies for Pipe & Blown Film
45. Auto Gauge Control for Blown Film
46. Auto Gauge Control for Flat Dies
47. Biaxial Film Orientation
48. Film/Sheet Thickness Sensors
49. Density Separation of Mixed Waste
50. Computerized Color Matching