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Strange tooling gelcoat delamination

http://www.talkcomposites.com/Topic39730.aspx

By mporta71 - 1/7/2021 8:24:17 AM

Hi,
Please see pics below of the mould and the part after infusion.
The mould has been applied 6 passes of easylease, 1 pass of wax and 1 mist of pva before laying fabrics.
All the timing between passes has been respected, and pva was left overnight to dry.
Composite spray glue from ec has been used to keep the fabric in place.
When it came to extract the part, some small areas detached as they should fine but the majority had the gelcoat stuck on it, as visible in the pic.
I was afraid of a long sanding job but tried first with a chisel and small strokes and with much relief chips by chips all the stuck gelcoat came away with leaving a glossy part surface.
My questions is:
- what could be the reasons why the gelcoat was so adhered (I use adhered and not bonded because with some mechanical force the gelcoat separated) to the part? 
By mporta71 - 1/22/2021 2:57:39 PM

 
oekmont - 1/22/2021 1:12:21 PM
I would start with the curing time of the gelcoat, because this is definitely a problem. And it seems like the gelcoat did cure, or were the flakes still tacky? I don't see a reason to believe that this is caused by the silicone.

The gelcoat is definitely hard but:
- despite 6 passes of easylease and 6 passes of wax in the mold, it has adhered to the part (can be removed by chipping carefully with a scalpel)
- the reinforcement on the cured gelcoat, laid to make the mold, almost did not adhere to the gelcoat. The explanation for this is for sure, as Hanaldo said, the sensitivity of epoxy gelcoat to its overcoat window.