Explain why a rubber washer stops sealing tightly after several ...

[dbose]

Explain why a rubber washer stops sealing tightly after several years.
 
  What will be an ideal response?

Question 2

Why would fluorocarbon elastomers be so effective in resisting solvents?
 
  What will be an ideal response?

[srodz]

Answer to Question 1

Over time the rubber is going to continue to crosslink and become harder which will not be as compliant with the other surface. This will also cause it to become more brittle and eventually break. It could also degrade.

Answer to Question 2

As with fluorocarbon molding resins, the presence of fluorine in the elastomer reduces all chemical activity, including solvation effects. This occurs because of the strength of the carbon-fluorine bond and the tightness with which the fluorine electrons are held. These tightly held electrons and the strong, short carbon-fluorine bond mean that the fluorocarbon molecules are repellent to attack from other atoms or molecules. Hence, their solvent resistance is extremely high.

[dbose]

Wow, this really help

[jackie]

Thanks for the timely response, appreciate it