Why didn't flash freezing make the polycaprolactone plastic brittle?

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SUMMARY

The discussion centers on the behavior of polycaprolactone (PCL) when subjected to flash freezing using a cooling bath created with dry ice and 99 percent isopropyl alcohol. Despite the cooling bath reaching approximately -77 degrees Celsius, which is below PCL's glass transition temperature of -60 degrees Celsius, the material did not exhibit brittleness after being frozen. The key conclusion is that reaching the glass transition temperature does not guarantee that a polymer becomes brittle; rather, it indicates a change in the mobility of polymer chains without necessarily resulting in a brittle state.

PREREQUISITES
  • Understanding of polymer chemistry, specifically the behavior of polycaprolactone.
  • Knowledge of glass transition temperature and its implications for material properties.
  • Familiarity with cryogenic cooling techniques, including the use of dry ice and isopropyl alcohol.
  • Basic principles of material science related to elasticity and brittleness.
NEXT STEPS
  • Research the molecular structure of polycaprolactone and its thermal properties.
  • Explore the concept of glass transition temperature in detail and its effects on polymer behavior.
  • Investigate alternative methods to induce brittleness in polymers, such as varying cooling rates or using different solvents.
  • Learn about the mechanical testing of polymers to quantify changes in brittleness and elasticity.
USEFUL FOR

This discussion is beneficial for students, educators, and researchers in materials science, particularly those interested in polymer behavior under varying thermal conditions. It is also relevant for hobbyists conducting experiments with polymers in educational settings.

R_Lee
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Hello, I am working on a science fair project with my son. His project is about the mobility of polymer chains depending on temperature and pressure. As part of his project we want to flash freeze a piece of plastic to show how brittle it becomes. We bought instamorph, which is polycaprolactone. It has a glass transition temperature of -60 celsius. Next, I bought some dry ice, put it in a plastic bottle and poured 99 percent isopropyl alcohol into it to create a cooling bath. This cooling bath should be about -77 celsius right? Lower than the glass transition temperature. So then I dipped the piece of plastic into the bath, held it there for about 30 seconds and pulled it out. I tried to smash it to test the brittleness but it didnt break. It felt the same, but just cold. Why is that? And how can I make it brittle?
 
Chemistry news on Phys.org
"Glass transition" does not mean that a material becomes "brittle."
 

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