I have a hollow plastic mold that I want to "fill" with something to make it about as hard as wood. This is partly to reinforce a thin plastic construction but also to ensure screws hold properly.
I've been considering casting with concrete, plaster, polyester, or epoxy, or trying with foam sealant. The solution must be "waterproof," meaning it must not absorb water.
The volume is about 2 liters, so it’s not a big item. The problem is that I don't have large openings to get the filling through, so it needs to be thin-flowing (especially since there are a couple of narrow passages inside the mold as well, imagine an hourglass shape; I only have an opening at one end).
From what I’ve read, polyester shrinks 5% when curing, so that doesn't seem sensible (there will be too much gap). Epoxy seems to be very expensive compared to the other solutions...
I suspect foam sealant might be difficult to get into the lower part of the mold if I can't get the nozzle past the narrow passages in the middle.
How does cement turn out if used without ballast? Will it be too brittle?
Both cement and plaster are likely to crack if I screw into them after they’ve set, but it might work to insert the screws before they’ve fully hardened (the screws don't need to be tightened hard; they’re more or less just to take up lateral forces, think "hanging").
Is there any other alternative?
One option, of course, is to try replicating the entire structure in solid wood, but that requires a lot of work, skill, and tools that I don't have. That’s why I’m hoping to find a good solution with some form of "casting mass."
I've been considering casting with concrete, plaster, polyester, or epoxy, or trying with foam sealant. The solution must be "waterproof," meaning it must not absorb water.
The volume is about 2 liters, so it’s not a big item. The problem is that I don't have large openings to get the filling through, so it needs to be thin-flowing (especially since there are a couple of narrow passages inside the mold as well, imagine an hourglass shape; I only have an opening at one end).
From what I’ve read, polyester shrinks 5% when curing, so that doesn't seem sensible (there will be too much gap). Epoxy seems to be very expensive compared to the other solutions...
I suspect foam sealant might be difficult to get into the lower part of the mold if I can't get the nozzle past the narrow passages in the middle.
How does cement turn out if used without ballast? Will it be too brittle?
Both cement and plaster are likely to crack if I screw into them after they’ve set, but it might work to insert the screws before they’ve fully hardened (the screws don't need to be tightened hard; they’re more or less just to take up lateral forces, think "hanging").
Is there any other alternative?
One option, of course, is to try replicating the entire structure in solid wood, but that requires a lot of work, skill, and tools that I don't have. That’s why I’m hoping to find a good solution with some form of "casting mass."
It will more or less become a kind of cylinder, the screws are mainly to prevent the plastic from rotating around the hard core (because then it doesn't "feed").
Expanding concrete sounds quite good... I hadn't seen it, it doesn't seem to be available in many places. The question is how well it works to pour into a 12 mm hole, the one I found at Finja had 0-4 mm sand in it, which feels a bit coarse...
Expanding concrete sounds quite good... I hadn't seen it, it doesn't seem to be available in many places. The question is how well it works to pour into a 12 mm hole, the one I found at Finja had 0-4 mm sand in it, which feels a bit coarse...
Ah, carelessly checked by me, I thought I came to the homepage and started clicking through the menu directly.
But it was quite expensive... 129 kronor per bag at K-Rauta anyway. Feels a bit pricey when you only need 2-3 liters... I'll have to think about it, maybe I can find something else to use the rest for.
But it was quite expensive... 129 kronor per bag at K-Rauta anyway. Feels a bit pricey when you only need 2-3 liters... I'll have to think about it, maybe I can find something else to use the rest for.