Is this pre-preg?

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#1

This is my first post, and I want to thank everyone for the information that they provide on here. It has been great help.

On to the post. I came across this video last night and couldn’t stop thinking about it while going to bed. In the video at 6:08 you can see what looks like fabric placed into a envelope bag, followed by resin that is poured in and squeegeed around. Next he cuts the shape out. What I can’t tell, is if time elapses from when he stops squeegeeing to when he cuts and if the bag is put under a vacuum and heat sealed almost like a vacuum food sealer you would see at Walmart.
If this is a method of making a poor mans pre-preg, what exactly is the hardener? Would the epoxy resin even be the same?
Thanks in advance!

http://www.youtube.com/watch?v=ZT51_P3m8Hs

#2

i say yes…poor mans prepreg. DOn’[t think you need to vacuum it out, since the rest of the video looked like wet layup. Might be just to cut the shape, but it’s still liquid. shrugs email the company :slight_smile:
psL he might put it in a freezer to cut it and save the shelf life. We did that here on a project. Wet layup, freeze the preform, cut it, cook and cure it

#3

Thanks, I will experiment around with this. :smiley:

#4

What would be the ideal material to use as a backing? What type of plastic is currently used on prepregs?
Thanks

#5

Vacuum bag works well. We have an old roll that may or may not have holes, so rather than risk it we use it as backing or as a poor mans mould release on plates (can get a kinda gloss finish too).

Pre pregs often have a type of grease proof paper backing on one side too. Just make sure to put the non stick side on the resin side.

#6

Would LDPE .006" film work? part#8553K503 from mcmaster.com It’s $23 for 48"x100’ allot cheaper then vac bags.

And about that gloss finish. When I lay these up on my glass table, how will I ensure that I wont have any pin holes or imperfections on the surface? Even if I use real prepregs.

And yes I will be bagging and putting these under vacuum, my table is also heated.

To me the surface finish has the same chances of having imperfections as when I vacuum bagged. I now infuse. And my brain is wired to think that the mold needs that front line of resin to act as a squeegee to push all the remaining air out.

#7

The LDPE should work, just test it before getting too carried away to check. Like I said, the bag we use is no good for making vac bags any more otherwise I’d get some other plastic.

Glass gives a better finish for sure, we just use bag on our big aluminium plate so we don’t have to clean it between jobs.

To get guaranteed zero pin holes you need you apply more pressure than just vacuum to real prepregs ie: use an autoclave. At the higher pressures the air that remains dissolves in the resin like CO2 in beer

#8

Large aluminum plate. :eek: How much did that cost? And why would it not have to be cleaned like glass?

Thanks for the explanation on the Co2 and Beer. I had no idea that’s how the small pin holes are removed. It was my hope that the vacuum would be enough combined with the heat. But now I am rethinking if I should going threw this hole process.:frowning:

#9

I have an 8’x 4’ aluminium Plate that is 3/8 " thick that I lay up any flat sheet on, I find it to be flatter than the Glass that I used to use, Get a slightly Matt finish in the surface tho, polishes up very easily to a high gloss tho. dont have a problem with pin holes when Vac bagged on it either.

#10

Just have to be carefull not to scratch the surface of the table when cleaning tho, I have twouble keeping the apprectice away from the table with a scraper blade!

#11

I think as long as you do it well, you can scrape things clean and without issues. Luckily, most resin bits are on the edges. I use a sharp steel scraper on my PP plastic table top. It’s seen it’s days, but still not that bad considering. of course, if you have a sanded finish on your aluminum,and you scrape cleanly, the aluminum will show streaks…

Hmm, now that I think about it, what about using an adhesive backed release liner? If it goes bad, just replace it, not your tool!