Equations? any ideas how i should tackle this?

Question

a thick section of rubber was found to be undercured when vulcanised for 10 minutes at 150c. an attempt was made to overcome this problem, the vulcanisation temperature was reduced to 130c.

what is the new cure time at the lower temperature?

Answer 1

This is a very complex question. If you have the rate of chemical reaction equation for this process, then you have a chance of determining the expected answer.

You are going to have so many variables to consider.
1. How thick is the rubber?
2. How concentrated is the sulfur (meaning what is the ratio of latex to sulfur)?
3. How cured is cured? Vulcanisation is a process that results in the formation of a cross-linked polymer
4. Rubber (elastic) bands have low cross-linking; the old black car battery case was highly cross-linked; so it depends on what the rubber is to be used for as to how "crosslinked" it needs to be and therefore how much sulfur needs to be added.
5. the relationship between the rate of the chemical reaction and the applied temperature is likely to be quite complex.

Beyond the above, I cannot answer you question. I don't know the Rate of the Chemical Reaction equation. I won't research the web for it.

But, I will say that lowering the temperature from 150 to 130 celsius could have strange effects.
It could:
- less cross-linked, therefore less cured irrespective of time
- the cross-linking may not even occur - too cool(?)
- to get the appropriate curing may take 2, 3 5, 10 or more times your 10 minutes.

Like I said, a very complex question.

If anyone can provide equations for the rate of the chemical reaction for the vulcanisation process, I sure some of us could solve the equation.

BTW - we'd probably have to know the thickness of the rubber as part of the rate law.

ex-Senior High School Chemistry (and Physics) teacher

Answer 2

As stated by someone else, there is a lot of data missing from your question. We don't even know in what time curing was effected!

However, roughly speaking, you would need to double the curing time for a 10 degree (Celsius) drop in temperature, so at 130 deg., you're going to need at least 4x10 = 40 minutes to effect a cure.

As a matter of interest, the only reason you would wish to reduce the temperature from the ideal (about 152 deg. C) would be in a complex moulding in order to permit the unvulcanised rubber to flow into the more intricate parts of the mould.

Answer 3

150 / 130 = 1.1538

10 x 1.1538 = 11.538 mins

I'd say 11 mins and 32.28 seconds

I'm sure there is an equation for curing of rubber, the Arhenius equation or something.

Answer 4

add 12.5% on to the 10 mins and you wil get your answer!