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I'm looking for a material that will expand to fill a cavity of an irregular shape, and then solidify into a permanent shape. I am not using it primarily for insulation purposes.

Polyurethane spray foam would be otherwise perfect if it were not for its stickiness, but I must be able to easily remove it afterwards without damage to other materials.

fred_dot_u
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goweon
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1 Answers1

14

Fill a plastic bag with the polyurethane spray foam. The stuff expands a ton, so be careful not to burst the bag.

popham
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    This is exactly what they do to make a mold for an F1 driver's seat. Start with a metal seat shape. Lay out a plastic bag in it. Driver sits down. Bag filled with foam. Carbon fiber laid over the foam shape to make a custom fit seat. Driver doesn't get stuck to foam or metal seat form. – FreeMan Oct 21 '23 at 12:10
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    I've used "expandable foam packaging bags" using "the foam-in-bag process" that come with the bag already sealed closed, and the "right" amount of foam precursors in much smaller (and weaker) bags inside. – David Cary Oct 21 '23 at 17:27
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    Old school fitting of ski boots. – D Duck Oct 21 '23 at 18:35
  • I'll give it a try, but it might be difficult to stuff a bag into some small awkwardly shaped gaps – goweon Oct 21 '23 at 22:29
  • @goweon, the more information you provide, the better the answers. If you're skeptical, then you should refine your question or ask another question. – popham Oct 21 '23 at 22:31
  • @goweon You can use more than one bag. Have a practice outside where it won't matter if the foam expands more than you're expecting and spills out. – Andrew Morton Oct 22 '23 at 10:58
  • I gave the plastic bag a few tries, and couldn't get satisfactory results. The plastic prevents moisture from entering and curing the foam deeper into the structure. And the plastic also prevents the foam from wrapping around or filling small features (~3mm) very well. I'm gonna accept this answer for now, but I'm going to look into some release agents, but the cleanup will be interesting. – goweon Nov 05 '23 at 16:38