Epoxy molds and ooa prepreg

General Composites Discussions Composites Talk
#1

Ok as some of you know I’m a noob. And when it comes to anything outside your typical stinky poly gel coat and infusion epoxy I know even less. However I think I found some good information for those who are like me and trying to step into the unknown. So if you read I please chime in and comment if I’m missing something because I honestly tried to research as much as I could to fit my needs.

Here are my needs for all my components moving forward since I need to buy 5 gallons of this stuff for some of it.

-Heat resistant up to 250f or 120c roughly. That’s for the out of autoclave cure from easy composites.
-No crazy ramp up for curing the ooa prepreg or molds because I don’t have an oven, nor can I figure out right now how to evenly heat my oven with coils embedded into the mold itself. However I am paying someone with a large oven to cure my finished product. I’m trying to make it as easy as possible.
-Located in the USA due to shipping costs “excluding the ooa prepreg”.
-Mold construction of a room temperature cure for the most part.

So with these things in mind I’ve come up with a list of items. My end goal is to make some car body panels which I will need help with my stack since the whole purpose of this is to use honeycomb. That’s another topic because I have no idea what thickness to use, hoe close to the edge you can run it, how many layers on each side, and also aramid or aluminum honeycomb… However here’s my starter list from freeman tool supply and easy composites.

Freeman 705 resin with 45 minute hardener. This tooling gel is good to 250f it says.
Renlam 5052 resin with hardener. I’ve been reading I think this can withstand over 100c but on the data sheet it says something like glass transition temp, 4 months 23c + 4h 130c. I assume that 23c at 4 months then you can post cure it for 4 hours at 130c, and in the two columns after that it shows tg onset 106-112 and tg 120-132. What is the difference between tg onset and tg?

Now I could go with a high temperature epoxy, but then I would need to post cure it to use the mold right? I like the renlam because it seems like I can room temperature it and use the mold fine for infusion, then if I wanted to use it for ooa prepreg I could post cure the mold.

Any thoughts? Sorry not much of a list of materials for this but it’s a start.

#2

Dont completely rule out just using a vinyl ester mould. I know Easy Composites say it isnt compatible, and for truly 100% perfect results it isnt. But Ive been experimenting a lot with the X-Preg since its release, and I dont think the results from a vinyl ester mould are too bad. Many people would be perfectly happy with the finish, but of course because it isnt technically perfect Easy Composites have to say that it isnt compatible. I think if epoxy tooling is too difficult to source good materials, just go with vinyl ester. Especially because being new to pre-preg, you aren’t likely to get perfect results straight away anyway, especially if you arent using your own oven.

#3

Cool man yeah I was reading late last night some old posts and remember you chiming in since my other main concern was getting epoxy to stick with fibers around corners and such. I’m going to try and locate a vinyl ester gel coat and lamination resin that can withstand 120c or 250f. Do you have any recommendations?

#4

My plan also is to clear coat the parts after so a perfect part isn’t really needed. However pin holes could be a major issue…

Have you tried their low cure cycle or cured to different temps rather then the recommended ones with good results?

#5

Yeh you dont need a vinyl ester that can handle 120, the results get worse at higher temperatures. You need to use the low temp cure cycle.

#6

Ahhh ok. I thought the opposite would be true…

Thanks man.

#7

Just my two cents, but I think you may save yourself a lot of work and frustration if you spend the extra time to get the plug and mold perfect. After making some molds that were “almost perfect” and then spending days sanding/clear coating/sanding/clear coating, I am now going back to fix the molds. I wish I had done them right the first time. Another lesson.