Hi there

Speeding up cure time can lead to more pinholes.. You need to know the best temp for the resin to flow through the material then get to the gel stage before you ramp up to speed up the cure time. That will take some experimenting with the material. I use a very very good OOA pre-preg which has a cure cycle with a suggested ramp speed. But for the best results I have worked out a cure cycle for my oven and my parts which works perfectly. Although it is quite different to the suggested cycle. It took me about 6 months of testing to work out the best cure cycle and breather stack. Even placement of peel ply makes a big difference so you need to have a play with a simple mould and use that mould for each test.. 

The reason for the low temperature is as morepower suggests.  For surfacing pre-pregs we tend to go for longer to allow the mould to heat up rather than using set ramp up times as most moulds tend to warm up at a sensible pace naturally when placed in the oven.

For example for resin flow reasons you should always dwell the ramp up at 80C for an hour for best cosmetic results. You can then increase it to for example, 120C for 1 hour to cure if time is of the essence.

When using our Easy-Preg Surface Layer PrePreg Carbon with the Vari-preg we always increase the time, eg 10hours at 100C is a typical single temperature cure we might use.  You could ramp it up and dwell at 80C for a couple of hours then do a quicker high temperature cure, but in our experience allowing the resin to flow is key to a better cosmetic finish.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Hi Garry,

Our Easy-Preg and Vari-Preg systems are not low temperature cure prepregs (I would say a low temp cure prepreg is widely considered to be around 60'C); really they're reasonably typical of a medium cure temperature prepreg and are specifically designed to have long out-lives. We send the prepregs all around the world and Germany, being a near neighbour, is certainly very realistic and cost-effective for us to dispatch to. I don't know of any suppliers or manufacturers of OOA prepregs with a similar performance in Germany.

For a quicker cure cycle that will certainly yeild perfect results using our Easy-Preg Prepreg OOA Surface Layer I would suggest the following:

1hr @ 50'C
1hr @ 60'C
1hr @ 70'C
1hr @ 120'C -- > Cool to ambient.

This is a 4hr cure cycle which will give you flawless, pin-hole free results and achieve a cured laminate Tg of 120'C too. You will of course need tools that can take (and have been prepared for) 120'C.

I hope this helps, all the best,

Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Hi Matt
Thanks for the info, Im used to working with prepregs in motorsport and aircraft use and everything is cured in clave,s and then usually post cured at 200+ so Im trying to figure out what i can reliably do at the workshop.

Thats great news that I can get the easy-preg material delivered to germany, Im in cologne so its not far too travel for a courier. And thanks for the cure cycle, the ovens ive bought have variable temp rate controllers so this should work out well.
One question I do have is has any one tried your mould material to 120degrees? Im hoping to use your mould material to make the first parts prior to getting some high temp epoxy block tooling machined.

Thanks
Garry

Hi Garry,

if you are referring to the Unimould system then the answer on a 120 degree cure would be yes and no! The design temperature is 80°C, at 80°C the service life of the tool will be almost indefinite, however we have on occasion pushed the tooling to °C with good results (but never higher), as you are well beyond where it is intended to be used I would be prepared to expect the moulds to degrade more quickly and potentially lose some dimensional accuracy. I very steady ramp up to the 120°C (say 10°C/hour) to post cure the mould before use would be essential to prevent the mould from off-gassing and softening whilst in contact with the prepreg.

You are in experimental and out-of-parameter territory sotry this at your own risk!  My advice would be to stick to the 8hr @ 80°C. You will probably find that with most ovens this will actually use less energy than 2hrs @ 120°C

Paul Statham
Easy Composites / Carbon Mods - Technical