Polymer chem, help plz.?

Question

Someone answered but it made no sense.

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The first order rate constant for the decomposition of diethyl peroxide has been reported to be around

1.0x10^14 * e^(-35,000cal/RT)

Predict the temperature range for which diethyl peroxide would be a good initiator.

Please explain steps...thanks, all.

Answer 1

I was sure that I answered this Q hours ago, but do not find it anywhere. So

The initiator needs to give a certain % decomposition in a usable time period. For something like epoxy glue you would want the fast setting workable time to be 5 minutes and the strongest bond (longer polymer chains from lower initiator) about 3 hours or so. Assume the time is related to 50% dissociation. What temperature are needed to give the two times? This will be the workable temperature range.

The 1/2-life of a first order reaction is given: t=2/k where k is in 1/time. t is usually expressed in seconds and k in 1/sec.

The Arrhenius value  A (1.0E14) has units 1/sec here.

Thus ln(300 sec) = lnA -35000/RT; solve for T

do same for 3 hours.