Talk Composites - The Forum for Advanced Composites

Too soft silicone

http://www.talkcomposites.com/Topic11452.aspx

By John. B - 5/24/2014 11:54:32 AM

Hi,
I've just made two moulds using CS2 condensation cure silicone rubber using the same pattern.
After 24 hours to cure, one has come out fairly hard (which is OK) the other is quite soft (too soft) 
I was very careful in measuring the catalyst ratio, (These were done at different times with different batches of silicone)
Any idea what seems to have gone wrong?
John. B 
By Warren (Staff) - 5/27/2014 3:55:14 PM

Generally speaking the CS2 is a good firm curing silicone with few inhibitants. 

Is there anything different about the two parts you are moulding??

There could be variation in mixing quality, temperature on curing etc that might mean you had been hovering around the threshold for a good cure.

To remedy the problem now, try adding heat and seeing if you can cook off the silicone at around 40-60C. If after several hours there is no improvement then you might have a problem.