Hi Cole,
Once you hit 100+deg you are really into specialist tooling, if you're going to use prepreg and autoclave then you have to design your moulds specifically for that application with the correct materials. Take a look at tooling prepreg, typically it has a lower temperature initial cure (60deg or so) so you can make the mould using normal materials for the buck then you can post cure up to the required temp without too much fear of distorting the mould. If you are using hi temps and ali or steel then are the dimensions critical? These materials the coeficients of thermal expansion of ali and steel are significantly different to carbon.

The other factor is cost, a decent hi temp mould will cost many hundreds if not over a grand a square metre. If you're only going to get 10-15 pieces out of it then is it really worth it (unless you are making F1 parts!). If you are making car specific parts then the sale life of the product will be limited to only a few years so may not be worth it or even get your tooling cost back.

Not sure why you are looking at 120+ resin systems but you also need to look at the Tg of the resin once post cured as this can be significantly higher than the post cure temp, again resin dependant so you can get the temperature restistance you need without curing or post curing that high. Something like a bonnet can actually post cure on the car.

Chris.

yeah i thought as much. i dont want to make a load of moulds suitable for infusion but no good when it comes time for me to upscale to pre preg

What your supplier is telling you is correct, with out of autoclave prepreg you can properly cure from around 100°C but for autoclave it is mostly inbetween 120°C and 160°C

i was on the easycomposites site and noticed that the unimold gelcoats are only good up to 90deg c.