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Old 02-04-2017, 12:50 PM   #1
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Default Questions about DIY prepreg and thermo-set resins

My process is currently 100% wet layup using epoxy resins, two sided closed mold using a high pressure bladder. There is a fair amount of detail, and the use of any kind of of breather material is difficult or impossible to remove from the finished part. Current resin is Resin Research 2000CE and various speed hardeners.

I would like to attempt a few runs using DIY prepreg, which would allow ample time to trim and work with the laninate before it is closed and cured. I understand there are many ways to approach this technique, which leads me to the question(s).

Method 1) reinforcement material pre-wet out using thermo-set resins. This would allow longer storage, ease of cutting shapes from templates, but is less cost effective and difficult to source thermo-set resins.

Method 2) reinforcement material pre-wet using standard epoxy resin with extra slow hardener and placed in a freezer for a short period, removed and cut from template and immediately cycled into the mold.

Method 3) using commercially available prepreg material. This would be the least cost effective method, and I have less control over resin ratios.

The current molds are capable of approximately 250 degrees f, but many prepregs and thermo-set resins require greater curing temps. Any input is greatly appreciated.
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Old 02-05-2017, 07:21 AM   #2
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I have a question about method 1, you said thermo-sets are difficult to source. Aren't epoxy resins thermosets ? I use method 2, but with open molds and vacuum bagging. Known as wet preg. My resin (medium hardener) wetted out fabric stays good for a week in the freezer at -30degF.
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Old 02-05-2017, 02:53 PM   #3
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Quote:
Originally Posted by jjcomposites View Post
I have a question about method 1, you said thermo-sets are difficult to source. Aren't epoxy resins thermosets ? I use method 2, but with open molds and vacuum bagging. Known as wet preg. My resin (medium hardener) wetted out fabric stays good for a week in the freezer at -30degF.
What's the advantage over this method? I can't see it other then maybe cutting difficult patterns but even that you'll stil have more pin holes then infusion and such. Basically it would be the same as wet bagging in the sense.
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Old 02-05-2017, 06:18 PM   #4
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A little more info; my current molds are questionable at the required temps that most prepreg resins require. As I am unsure if the switch to prepreg will improve the process (or be worthy of the additional expense), I would like to attempt other options first. I though of using slow or extra slow hardeners (all on-hand) and pre-wetting the reinforcement out and then placing it in the freezer.
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Old 02-05-2017, 08:37 PM   #5
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Just buy some real pre preg. It easy to get in USA.

A proper pre preg will be easier to cut out the pieces you need as a DIY pre pre preg with normal laminating resins will still be a sticky mess!

There are pre pregs that can cure as low as 65C although they will take a long time to cure. Any cheap mould should still be good for an 80C cook.
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Old 02-07-2017, 07:16 AM   #6
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He said it was a closed mold and using a bladder. I don't think infusion would be possible?
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Old 02-07-2017, 09:23 AM   #7
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Quote:
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He said it was a closed mold and using a bladder. I don't think infusion would be possible?
I have looked at the mold/part and it appears that infusion wouldn't be an option, maybe it is but I can't figure it out. The part is molded as one piece, so it would be impossible to remove any breather material from the inside of the part, which gets filled after de-molding.

Basically what I am looking to do is figure out a better way to prepare the reinforcement material. I currently cut shapes with a template, but the carbon (or fiberglass) will begin to fray as it is worked with and wet out in the mold. I was hoping to pre-wet the material, place it between plastic (similar to prepreg), and place it in the freezer. Once it is chilled it can be removed and cut to shape and inserted in the mold.

I have not been able to source prepreg at a price that makes it a cost effective alternative.
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Old 02-07-2017, 09:52 AM   #8
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Have you seen this video?

https://www.youtube.com/watch?v=9_tDQTgdsCg
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Old 02-07-2017, 06:08 PM   #9
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Maybe you should try the weave set carbon, this will help prevent the edges from fraying?

Pre preg is still the way to go, obviously your time is not a factor in cost as messing with wet layup will take much longer than the simplicity of pre cut pre preg pieces that will have neat edges and are ready to go. Plus also being xxxxloads stronger than typical wet laminating resins. I understand it would seem a lot of trouble though if you are not set up with oven, high temp release system like Frekote and all this costs too $$.
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Old 02-18-2017, 08:18 PM   #10
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I have watched the video but there is no mention of what type of resin they are using, how they store it. I attempted a test piece with slow hardener, letting it gel up followed by placing it in the fridge, when I attempted to release from the film it was still very gummy.
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