Styrene + Resin Question

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Thain

Sr Member
RPF PREMIUM MEMBER
I'm working on a kit modification project in which I need to make two pieces from scratch. I am going to make them from styrene, glued together with Tamiya cement, but instead of molding them and casting them as solid resin pieces, could I just cut a little hole in the pieces and fill them with Smooth-Cast 320, making them solid? Since they are one-offs, I'd prefer to not have to use material to mold them, but my worry is that the heat of the curing resin will warp the styrene.
 

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renaissance_man

Sr Member
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I'm working on a kit modification project in which I need to make two pieces from scratch. I am going to make them from styrene, glued together with Tamiya cement, but instead of molding them and casting them as solid resin pieces, could I just cut a little hole in the pieces and fill them with Smooth-Cast 320, making them solid? Since they are one-offs, I'd prefer to not have to use material to mold them, but my worry is that the heat of the curing resin will warp the styrene.
If you haven't already sealed up the piece, I would use a piece of sandpaper to rough up the internal surface to allow the resin to key to it when you pour it inside. If you don't have a piece of sandpaper to hand you can use a craft knife/blade and put score marks into the internal surface again to give the resin something to really anchor to.

How thick is the styrene and how fast does the resin cure?

If the styrene is 2mm or thicker you shouldn't have a problem provided you swill it around inside and try not to let it pool in one place as the heat build up may effect the styrene and causing some warping.

IKB1806, Plaster of Paris is just as exothermic and I don't think it will adhere to the inner walls of the styrene as well as resin.
 

Thain

Sr Member
RPF PREMIUM MEMBER
They are these ear pieces on each side of this helmet. I want them to be solid so I can screw them in from the inside, also giving the helmet more weight.
IMG_2343 (1).jpg
 

Thain

Sr Member
RPF PREMIUM MEMBER
If you haven't already sealed up the piece, I would use a piece of sandpaper to rough up the internal surface to allow the resin to key to it when you pour it inside. If you don't have a piece of sandpaper to hand you can use a craft knife/blade and put score marks into the internal surface again to give the resin something to really anchor to.

How thick is the styrene and how fast does the resin cure?

If the styrene is 2mm or thicker you shouldn't have a problem provided you swill it around inside and try not to let it pool in one place as the heat build up may effect the styrene and causing some warping.

IKB1806, Plaster of Paris is just as exothermic and I don't think it will adhere to the inner walls of the styrene as well as resin.
I don't recall the thickness off the top of my head, but I think it's 2mm. I do know that the top and bottom of the pieces are two sheets thick, seen here:
IMG_2410.jpg
If I make sure to keep the resin moving, you don't think I'll have an issue with it warping, even as it's moving?
 

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ursus43

Well-Known Member
The heat of the resin as it reacts will probably warp your buck. Plaster of Paris will expand and explode the buck
 

Thain

Sr Member
RPF PREMIUM MEMBER
Ok, thanks for the input. I'll test small batches on a test piece first.
 

renaissance_man

Sr Member
RPF PREMIUM MEMBER
Pour the resin in multiple thin layers, this will reduce heat build up.
I second that motion.

Just mix about 30-40g/ml of resin depending on your type of resin and whether it mixes by weight or volume and do it the whole process in stages.

If your intention is just to slush cast some resin inside for added strength then you'll be fine, but if you want to make the part completely solid DEFINITELY do it in about 4-5 stages of mixing small batches and slushing it a few times.

Good luck.
 

cavx

Master Member
RPF PREMIUM MEMBER
2mm plastic would take a fair amount of heat. If you pour the resin to be no thicker than 3mm or 1/8", you will be fine. I'd say you can pour the resin up to 6mm or 1/4" before the exo becomes hot enough to make the plastic deform. Remember that these 2 part resins need to get hot in order to cure properly.
 

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