prepreg resin options

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#1

Hey everybody. I am new to the site and have been browsing for several days looking for information on this subject. I am making small parts for cosmetic use in automotive and motorcycle applications. I am wanting to make larger part eventually but want to hone myself with smaller things that cost less to screw up.

I have pretty poor working conditions as far as room temperature control. I work in an non insulated work shop, which means I have only a few weeks of good temps. The rest of the time my resin does not cure due to low temps or it cures while in the middle of an infusion, even when using very slow cure catalyst (120 min). I am wanting to find a catalyst that I can use with epoxy resins, both for infusion and possibly for some small batches of home made prepreg material.

My reasoning is this: I can spend HUGE amounts of money insulating, adding heating/cooling units and so forth in a work area that is hardly worth the time or money, or, I can put a small amount of that money toward building a smaller more easily heated “oven” and the appropriate temp control setup. The latter I think I have figured out.

I realize that prepreg material is readily available, but I am really interested in using carbon/kevlar and carbon/fiberglass for the color options. I have never ran across either of these materials in prepreg form. I do not know if I will ever need enough to special order anything like this.

I think that maybe I have already stumbled across these resin catalysts and or systems but might not know the appropriate wording and not know exactly what I was looking at, so if I have overlooked things I apologize.

The only other question I have regarding this topic(I am full of questions of course), is more of a curious thing that occurred during my first VIP. My shop temp dropped to appr. 40 degrees after infusion but before my resin passed B stage. After 2 days my part had not set. At this point I figured my part was a failure so I began playing around. Eventually I tossed it in the oven and cooked it for about 30 minutes at 150*F. Stupid thing cured and life went on. I realize this is not the correct method, but it got me wondering if a slow cure epoxy (120 min) was laid out in prepreg form, kind of like the video from david algie, and then frozen before passing B stage, to stall the cure. Then cured in an oven, would this actually work like I need? The part I ended up with is very rigid and looks like other carbon I have seen completed.

Thank in advance for any help and for reading my long winded ramblings

steve

#2

If you wirk with composites you need a room that ist temperature controlled. Most times a heating is enough. For hot days you can use very slow infusion systems with up to 2400min.
Prepregs also need a temperature controlled working area.

#3

I’m not sure I follow exactly. Prepregs are designed to be stable at normal temps and only cure when heat cured “x amount of time at x temp”. Prepreg is frozen when not used to lengthen shelf life. Prepreg also needs more than normal ambient temp to move in to full cure.

I’m not trying to argue, I’m sure I know very little overall about the composite world compared to most everyone here, however, it seems like prepreg and heatcured resin would do nicely for my current needs. .

Can anyone point me in the direction to source this type of resin in smaller quantities. I have found it in 55 gallon and tote sizes. Unfortunately it’s a little out of my budget and use needs at this time.

Steve

#4

I am confused on the “catalyst” bit.

Although in the USA they call POLYESTER curing agent a “catalyst” (which, technically it is not, but never mind) epoxy resins cure with “hardener” or “curing agent”.

For infusion you want a decent temperature in your workplace, to keep viscosity low.
For prepreg you want a certain temperature, to generate the right amount of “tackiness” to be able to work the stuff.
For the fibers you want a certain temperature (moderate heating) to fight off condensation.

I have my tools in an unheated shed at home, and it annoys the $%^$# out of me. Everything is wet and corrodes. Image the quality of fibers in that shed. (which is also why at work we have some 40.000 sqft (4000m2) of heated storage.

#5

You can look into Huntsman Adralite epoxy system. I have been using it for a good amount of time and in the winter time I made some prepreg and found that it took 3 days to gel if i left it outside which was about 0-3 degrees celsius. I think if I had a freezer I could make it last a week or more. It is an ETC Resin system.

You will need an oven if you use it though and cure times can range from 6 minutes to 3 hours or so. Ive had good results with it but it took me some time to get used to. I also recommend following the post cure cycle because it really made a difference in quality.

#6

Thanks for the responses.

Now I understand why I need the temp, having never worked with prepreg I hadn’t thought about the tackiness being a problem in colder climates. I also did not realize condensation could occur in the fibers.

By catalyst I actually meant hardner. Thanks for the input Herman.

C6design, I will look in to the Huntsman system. That actually sounds like exactly what I need. Oven curing will be easier to accomplish than reaching and maintaining 70* without spending a fortune.

Thank you for the help. Much appreciated.

Steve

#7

C6, can you specify which Araldite system you used? This helps Boostard a lot, as Huntsman has 1000+ epoxy systems…

#8

I too would like to know where Huntsman Araldite can be purchased . I need to build an intake manifold and saw that brand of resin was used in the making of some for Ferrari . From their website I have made a few calls , I have not received any return calls though . Also , the Araldite 2014-1 was used in the Lambo Aventador if i’m not mistaken .