New mould material

General Composites Discussions Composites Talk
#1

Hi everyone, sorry possibly another noob post here.

Today the guy at carbon mods told me the green epoxy tooling gelcoat and putty that i was using to make my moulds will start to deform if exposed to temperatures above 50°C. Im a bit disappointed as i was hoping to cure at around 80°C.

So i managed to find the following on the easy composites website, which according to their specs has a heat distortion temperature of 110°C - 115°C:
http://www.easycomposites.co.uk/products/epoxy-gel-coat/clear-epoxy-gel-coat.aspx

As most people here are a lot more experienced than me, may i ask if this would be ok to use for making my moulds, backed up by about 3 layers of hand laid carbon fibre rather than the putty?

Thanks

#2

Yes you can use it to make moulds. I would mix in a pigment just to make things easier to see.
What epoxy are you going to use for the layers underneath the gel coat?

What weight CF are you using? you’ll need alot more than 3 layers of 200gsm. Plus you’ll probably need to vac bag it while the epoxy gels. Personally i wouldnt make a mould from CF for your first go. Get a polyester gel coat, poly resin and some CSM fibreglass. Despite what easy composites say i find its easier to work with, reliable and makes mistakes less expensive. Remeber to wax the plug

I’ve never had any problems with fibreglass mould and CF/epoxy products so long as the heat is kept in check. Its always ready for demould next morning.

#3

Hi r0bsk1

The epoxy resin i was going to use is something like carbon mods’s laminating resin and just hand lay the carbon after the gel coat has gone off a bit so the surface is just taccy: http://carbonmods.co.uk/Products/Carbon-Fibre-Laminating-Epoxy-Resin---1kg-Pack__CMCFLR1KG.aspx

The only reason i suggested using the CF is because iv got a load of it already here, buy yes its 200gsm and a tad expensive to use loads of layers.

If the fiberglass can take the heat i think thats a great suggestion. How thick do you think i would need to make it?

Thanks

#4

My fibreglass moulds are about 5mm thick but they’re not that big. Something like motorbike fairing mould would need some structure to it to prevent flexing.
Can that epoxy take the heat you intend to apply?

Fibreglass can take the heat but its resin you’ve got to watch. It doest tend to go a little plyable but i’ve learnt by my mistakes and now know were to place it in relation to the heating element. Im not sure on the exacpt temp being applied.

#5

To reach your desired 110-115 degrees C heat resistance, you will nee to postcure at some 100 degrees (in incremental steps)

Your backing laminate will not like that, as the resin you mentioned only takes 80 or so.

You will need to postcure, as the not cured epoxy groups will co-cure with your part, leaving it stuck in the mould.

So get yourself a 110-115 laminating resin as well, to make the mould.

#6

Carbon mods also sell this resin which they say can take 140°C: http://carbonmods.co.uk/Products/Carbon-Fibre-High-Temperature-Laminating-Epoxy-Resin---1kg-Pack__CMCFLRHT1KG.aspx

So if I use the gel coat I mentioned earlier, then back it up with a fair bit of firberglass (as some of my moulds will be fairly big) using the high temperature resin and post cure the moulds that should do the trick?

The 110 - 115 is the temperature that the gel coat distorts at according to the easy composites website. I only need to go up to around 80°C to cure my parts which should reduce the cure time to 4 hours.

As I only need to go up to 80 what temperature do you recommend I post cure the moulds at?

Thanks

#7

always go for a full cure of the gelcoat. partial cures (as in: not reaching ultimate Tg) will give problems when releasing.

#8

has anybody has any experience with vinylester tooling gel coat as the mould surface layer when being used with epoxy resin? iv read that a polyester tooling gel and epoxy resin can cause some problems, is there anything to worry about with vinylester?