Hi there

i just did a few tests and I have a problem I already had a few days ago without finding the origin.
When demoulding I heard a lot of crrrrrrac (It was extremely difficult to demould) annnnd: 
photos worth more than words: 



As you can see resin sticked on the glass despite the use of chemical release agent so I'm wondering what are the differents possible reasons of this fail.... temperature? too early demoulding? fail when applying the release agent?
something else?

Since I'm here, what's the best way to cut Polypropylene Sheets? I'm thinking about using it instead of glass for the next time.

Thank you mates

Yeh sort of answered your own question there, could be any of those things. Its a release failure for sure, but without knowing exactly what you did and what you used, its pretty impossible for us to conclude what failed.

For cutting polypropylene, a jigsaw is probably the easiest. It will heat up and melt as you cut it, but the back of a razor blade makes pretty short work of deburring the edge afterwards. Polypropylene is no where near as good a tool surface as glass though, I'd definitely recommend persisting with glass and just getting the release issues sorted.

thank you for your reply

I did 6 differents plates and it was the only one to fail like this.
It was one on my first demoulding so I go for a too early demoulding.

For the polypropylene as a mould surface, I suppose the only difference to be the shining of the final part lower than the glass isn't it?
I ask this because I will sand and polish or make a top coat with xcr covering epoxy as a clear coat so in this case, is there any difference between poly and glass?
The interest for me of poly would be to invoid the release possible problems and poly is cheaper to replace when the mould plate is damaged with razor blade scratches to remove residues.

I perhaps should do another topic for this because it doesn t match with the title anymore ^^

Polypropylene sheet is great for low volume or occasional use.  Glass is what you will find used for most large production environments.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Thanks a lot for your answers