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32.6: Summary

Last updated

Nov 26, 2020
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- 32.5: Demostrations
- 32.7: Questions

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You should now be familiar with the following concepts:

Above T_g polymers are rubbery, whereas below T_g they are glassy
Rubbery behaviour arises from the polymer's ability to change its conformation at high temperatures
Glassy behaviour arises from the polymer's lack of ability to change its conformation at low temperatures
Many factors affect the T_g of a polymer. Some factors are to do with the chemistry of the polymer:
- chain length
- chain flexibility
- side groups
- branching
- cross-linking
- the presence of plasticisers
Other factors are to do with the method of measuring T_g:
- strain rate
- cooling or heating rate
You should also understand the theory of kinetics, which explains how glasses form and noted that there are many different experimental methods for measuring the glass transition temperature in polymers.
Finally you should have observed how the behaviour of a rubber ball varies when it is bounced above, below and near its T_g and seen how the behaviour of silly putty varies at different strain rates.

Going further

Websites

The Glass Transition
Part of the Macrogalleria based at the Department of Polymer Science at the University of Southern Mississippi.
Crazy Aaron's Puttyworld
Includes video of a huge ball of silly putty being dropped from a tall building!

Going further

Websites

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