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Author Question: Describe the processes of solvent/solute interaction that lead to swelling and, in some polymers, ... (Read 173 times)

madam-professor

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on: Aug 19, 2018
Describe the processes of solvent/solute interaction that lead to swelling and, in some polymers, dissolving of a plastic by a solvent.
 
  What will be an ideal response?

Question 2

Explain why plasticizers increase flexibility and elongation in plastics. What is the relationship between plasticizers and the glass transition temperature?
 
  What will be an ideal response?


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mbcrismon

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Reply #1 on: Aug 19, 2018
Answer to Question 1

Solvent molecules form secondary bonds with the polymer molecules, usually at sites on the polymer that are chemically similar to the nature of the solvent. When many of these secondary bonds form, there is sufficient energy in the molecules to allow the penetration of the solvent molecules into the polymeric structures. This causes swelling. If even more of the secondary bonds between solvent molecules and the polymer are formed, or if the secondary bonds are extremely strong, then the total polymer molecules can be separated from the other polymer molecules and total solvation occurs.

Answer to Question 2

Plasticizers are solvents that are added to swell and partially solvate the polymer. By swelling the polymer the plasticizer expands the polymer network and, therefore, allows the polymer atoms to move more freely. This greater mobility is seen as increased polymer flexibility and elongation. Raising the temperature above the glass transition temperature has the same general effect. Therefore, adding a plasticizer lowers the glass transition temperature.


madam-professor

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Reply #2 on: Aug 19, 2018
Both answers were spot on, thank you once again


mbcrismon

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Reply #3 on: Aug 19, 2018
Great! Please up vote :D


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