Rubber stiffness as a function of temperature?

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SUMMARY

The discussion centers on the relationship between rubber stiffness and temperature, highlighting that rubber behaves as an entropic spring, with increased temperature leading to increased modulus and stiffness. It notes the transition of rubber through glass-like, leathery, and rubbery states as temperature rises, which is evidenced by graphs showing modulus decreasing with temperature due to increased free volume. The conversation also addresses the dangers of summer tire compounds with high glass transition temperatures (Tg) becoming excessively stiff in winter conditions, emphasizing the complexity of modulus measurement across different phases of rubber.

PREREQUISITES
  • Understanding of entropic spring behavior in materials
  • Knowledge of phase transitions in polymers
  • Familiarity with the concept of glass transition temperature (Tg)
  • Basic grasp of modulus measurement techniques
NEXT STEPS
  • Research the effects of temperature on rubber modulus in detail
  • Explore the principles of phase transitions in polymer science
  • Study the implications of glass transition temperature (Tg) on material performance
  • Investigate the measurement techniques for modulus in different rubber states
USEFUL FOR

Material scientists, polymer engineers, automotive engineers, and anyone involved in the design and application of rubber materials in varying temperature conditions.

JJD
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I'm aware of the concept of rubber as an entropic spring and how increasing the temperature increases the modulus/stiffness of the rubber. I've seen the experiment of how heating a strip of rubber supporting a load will cause it to shorten.
But also a rubber will transition from its glass-like state to its leathery state then rubbery state as temperature increases. These graphs will show the modulus decreasing with temperature. I believe the explanation for this is the increase in free volume. Also, summer tire compounds (high Tg) will become so stiff in winter temperatures that they can be dangerous to drive on.
http://www.azom.com/images/Article_Images/ImageForArticle_12100(9).jpg
https://en.wikipedia.org/wiki/Time–temperature_superposition

These two things seem contradictory. I'm guessing it has something to do with how modulus is defined or measured in each circumstance. What am I missing?
 
Science news on Phys.org
Phase changes; "rubber" is a general word. Every time you cross a phase boundary you get a whole new set of properties.
 

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