Coil DD on poltstyrene.

[dgm]

Hello everyone, I wanted to ask what kind of resin I can use on polystyrene without melting it, to block the coils of a DD coil. Thank you for your kind suggestion.

[waltr]

Hello everyone, I wanted to ask what kind of resin I can use on polystyrene without melting it, to block the coils of a DD coil. Thank you for your kind suggestion.

Most epoxy is fine. Just do a test with a small batch of epoxy of a piece of scrap polystyrene to be sure.

[dbanner]

Epoxy no good, will affect polystyrene. I recently used high density polystyrene to make dd coil. I used first ordinary White glue to seal the PS, several coats. Then I used Ever Build all purpose ready mix filler to fill up the space where coils sit. Finally I used truck bed liner to paint and seal the polystyrene. The result is lightweight and very rigid and strong.

[Hyena]

Epoxy no good, will affect polystyrene. I recently used high density polystyrene to make dd coil. I used first ordinary White glue to seal the PS, several coats. Then I used Ever Build all purpose ready mix filler to fill up the space where coils sit. Finally I used truck bed liner to paint and seal the polystyrene. The result is lightweight and very rigid and strong.

This is strange, I am using HIPS (not this particular, but its the same material - https://www.curbellplastics.com/Rese...ct-Polystyrene) for vacuum forming, because seller told me, that it is nearly the same like ABS (according to forming temperature and plasticity) and I can confirm that it is almost the same like ABS. I use only few spots of hot glue gun to keep coil in place until epoxy harden. I am using this epoxy http://www.havel-composites.com/shop...385.html?pls=0
With this hardener: http://www.havel-composites.com/shop...min.html?pls=0

I had never any kind of problem. It stick on it well (inner surface of shell always well scratched with rough 60 sandpaper). From my experience it does not cause any kind of damage to PS.

Can you explain your problem with epoxy + HIPS or PS? Is your epoxy real epoxy? Isnt it polyester?

[Altair]

Seems me there is some misunderstand between Polystyrene and HIPS (High Impact PolyStyrene) the first one is usually used for paking, the second one is a different aspect material, e.g. CD casing.

dbanner, have you some photo of coil you made with Polystyrene?

[Hyena]

When it is HIPS, GPPS, foamed PS bubbles, its still the same material only with different additives. Might depend on additives, but basicaly its still the same solution.

[dbanner]

Seems me there is some misunderstand between Polystyrene and HIPS (High Impact PolyStyrene) the first one is usually used for paking, the second one is a different aspect material, e.g. CD casing.

dbanner, have you some photo of coil you made with Polystyrene?

yup, I'll post some photos in a few minutes, I should have mentioned that it was a one inch thick sheet of high density foamed polystyrene, which I cut out the shape of nice coil shell for DD. I then used old hot soldering iron to groove out the space for the two coils.
but the magic stuff was the Rust-O-leum truck bed coating, which provided incredible strength and hardness to shell. however it cannot be applied directly on to polystyrene( I tried a small piece and it did slightly melt) hence I painted foam with white glue, which dries pretty fast, before applying the truck bed coating.

[Altair]

yup, I'll post some photos in a few minutes, I should have mentioned that it was a one inch thick sheet of high density foamed polystyrene, which I cut out the shape of nice coil shell for DD. I then used old hot soldering iron to groove out the space for the two coils.
but the magic stuff was the Rust-O-leum truck bed coating, which provided incredible strength and hardness to shell. however it cannot be applied directly on to polystyrene( I tried a small piece and it did slightly melt) hence I painted foam with white glue, which dries pretty fast, before applying the truck bed coating.

Thank dbanner, great stuff!
From what I see, you use Foamed Polystyrene, not High Impact Polystyrene.
Moreover, not only solvent but also heat during epoxy curing could melt polystyrene...

[Hyena]

Thank dbanner, great stuff!
From what I see, you use Foamed Polystyrene, not High Impact Polystyrene.
Moreover, not only solvent but also heat during epoxy curing could melt polystyrene...

Guys, please do not mix epoxy and polyester resin. Epoxy does not create any heat, never! Its polyester resin, which will nearly burn in higher volumes!

For epoxy you actually need to add heat to cure faster/cure to withstand higher temperatures.

[Altair]

I know there are fast and slow cure epoxy, the first one could generate heat. I use only slow cure epoxy.

[Hyena]

I know there are fast and slow cure epoxy, the first one could generate heat. I use only slow cure epoxy.

Yes, but even fastest epoxy does not create any heat. Only polyester resin create heat.

[Goaty]

Yes, but even fastest epoxy does not create any heat. Only polyester resin create heat.

Epoxy curing is definitely exothermic.
I speak from experience as I have had many years repairing epoxy surf boards which are generally constructed by glassing over a polystyrene core of either EPS or XPS foam.
In surface laminations the heat can readily escape into the atmosphere but if a bulk mass of resin is used to fill a void in the foam the heat is unable to escape and will often reach a temperature high enough to melt the surrounding foam.
Heat build-up can be minimised by layering the resin, allowing each to set and cool.
Slow hardener helps to control the heat build-up but the correct mix ration of resin and hardener must always be maintained.

Polyester resin is also exothermic but it also quickly damages polystyrene by dissolving it. The rate of exotherm can also be controlled to a certain extent by reducing the amount of catalyst used as well as using thin layers.

Ambient temperature also greatly affects the curing rate of both resins.

[Hyena]

I have experience with polyester. Repairing canoys and fish tubs with fibre glass. Always in relatively thin layers so no problem with overheating. Container with resil always got very hot when you left few cm in it. I do not like it and use it only on boats and tubs.

My experience with epoxy resin is quite differrent. I do not have hardener which can cure in less than hours. I build compound bow limbs from wood and lots of fibre and epoxy, but I use epoxy which cures like 8 hours in 25°C, because I want wood to absorb as much epoxy as possible. Also with coils, I use epoxy with workability about 50 minutes. Its time, when I can add fiberglass into housing and also longer curing means more stable process. Null practically does not change during hardening. I am afraid that only high speed epoxy can get hot. My container with unused epoxy never changed temperature enough to notice it.

Which epoxy you used?
For coils, I would not recomend any fast curing whatever, because heat (or any change in density) will change dimensions and your null could not be called null anymore.

[Tibuck19]

sun cure uvc 2000 is a UV catalyst that you premix in polyester resin, the resin does not start heating till exposed to UV light and or sun light, once you expose it to sunlight it dries within seconds, thus no excessive heat build up.

[dbanner]

Guys, use what I recommend and see for yourself. It does not "pull" the coils when drying, null is not affected. You can see brand name in photo. Resin mixed with micro bubbles always have difficulty keeping the perfect null. What I show is extremely lightweight and strong, does not crack. Just squeeze out of tube directly into the coil shell, comes out of tube like toothpaste, dries hard like concrete, light as balsa wood. Then once dried, apply coat of varnish if you want or better yet, truck bed coating to resist scuffing and be waterproof.