Epoxy Etching from Alkaline Solution

I have client that uses the light from a LED with a clear epoxy end
and a phototransistor, housed in a similar clear epoxy package, to
measure the clarity of a soap solution. He is worried that in time
the clear surfaces of the devices will become cloudy during years of
being immersed in a strong soap solution. He wants to conduct a
year-long test, to determine if the solution etches the epoxy.
Couldn't a stronger hot alkaline solution, such as potassium
hydroxide, be used to accelerate his testing? Do you think his
concerns are justified? What other materials would be better than
epoxy?
David A. Johnson, P.E. --- Consulting Engineer
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David A. Johnson
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I would wory that the potassium hyroxide would not be a good mimic of the soap. The reaction(s) would be too different.
You are right about heating the solution to accelerate the test. Unfortunately you don't know how much faster a given temperature will be. The standard rule of thumb in chemistry is that a 10 degree C increase in temperature double the reaction rate. This corresponds to a fairly low activation energy ~ 13 kcal/mole, making the estimates fairly conservative.
John
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John Spevacek

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