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Old 02-07-2011, 11:40 AM   #1
southman

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Default Polyester Resin layup on HDPE sheets

I needed some help before I spend more time and money on a proto-type mold.

I was going to use 1/8" HDPE sheets for a proto-type mold. My part layup will be with polyester resin and fiberglass.

Has anyone used HDPE sheets or stock for molds and do you think the polyester resin will eat into the HDPE?

I plan to test some soon, but thought I'd ask before I tested.

Thanks in Advance.
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Old 02-07-2011, 02:06 PM   #2
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Polyester won't eat into HDPE but It might be too soft for mold material. My fingernail put visible scratches into the flat plate I used.
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Old 02-07-2011, 03:30 PM   #3
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thanks canyon.

Can you explain why you think it will be too soft? I know it's a soft material compaired to others but how would that effect the final part.

It's 1/8" and can get scratched easly but it will be tacked (nailed) down to plywood every 4-6". Basically it will act as a barrier between my plywood jig and will still have mold release applied before glass goes down.
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Old 02-07-2011, 04:30 PM   #4
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You don't need mold release with HDPE. I don't know what you're making but my fingernail scratches the surface and when I make test coupons I can see the scratch show up on the final part.
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Old 02-07-2011, 05:38 PM   #5
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The finish is not as important to me at this point than the resin reacting to the hdpe and giving me a warped final product.

I'll make some test samples and post up what I find.

The main reason I'm using this HDPE sheet is I have a good quanity that was free and it seems to be a good material for one-off/proto-type molds. (if I can make it work)

again, thanks
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Old 02-08-2011, 05:16 AM   #6
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If you are doing simple shapes, then you will be fine. Depending on what exactly you are doing, the vacuum might distort the shape as well. I used HDPE table top for my infusions (I do 99% of the time, flat panels), and the parts come right off. any excess resin, I CAREFULLY scrape off with a new razor/scraper blade. Used one for about 1-2 years now and it is showing the abuse....but, I don't care about surface finish.
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Old 02-08-2011, 06:30 PM   #7
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Quote:
Originally Posted by riff42 View Post
If you are doing simple shapes, then you will be fine. Depending on what exactly you are doing, the vacuum might distort the shape as well. I used HDPE table top for my infusions (I do 99% of the time, flat panels), and the parts come right off. any excess resin, I CAREFULLY scrape off with a new razor/scraper blade. Used one for about 1-2 years now and it is showing the abuse....but, I don't care about surface finish.
Riff - How thick is your hdpe?

My shapes are simple, if it works I'll post pictures. If not I'll hold my head down in shame.
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Old 02-09-2011, 06:24 AM   #8
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It should work. The only trouble you might experience is that when doing a polyester layup that will generate some heat, the HDPE can expand so much that it will not keep its shape. But that will be dependant on mould design and laminate thickness.
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Old 02-10-2011, 11:14 AM   #9
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1/2" thick, it's bolted down to a steel cart. Maybe if your parts are real simple, you can vacuum form them (ie: simple bowl shape, etc)
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Old 10-21-2015, 01:11 AM   #10
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Quote:
Originally Posted by herman View Post
It should work. The only trouble you might experience is that when doing a polyester layup that will generate some heat, the HDPE can expand so much that it will not keep its shape. But that will be dependant on mould design and laminate thickness.
I've managed to undertake it without any issues. But yeah, it's technically possible to expand.
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