Fiberglass resin, polystyrene & cement.

[busastars]

I have a little proect on the go with a fish tank, im making a 3D backround by carving polystyrene.

No something im not 100% on is fiberglass resin. Ive done patch work on a fiberglass car many years ago, from what I remember when mixed resin gets quite hot.

So I was just wondering would a mix of resin melt polystyrene?

I have read some people doing it this way BUT most use a skim of cement then resin the cenment to seal it.

The problem with using cement though is that it can if not done 100% push the PH up in the tank and I want to avoid doing this if possible, I do have a bag of cement here with colour additive just incase I do it this way. I have not got my resin yet.

Also anyone know the difference in marine & standard resin?

 

[rtbcomp]

You could try the potting compound they use for electronic components, this doesn't get as hot as normal stuff, but may cost more.

 

[Debs.]

Some (if not many) polyester or aliphatic resin systems will dissolve styrene based foams; although generally, it`s not an exotherm that would damage the foam armature/core, but rather it`s a chemical-solvent reaction with the resin or it`s catalyst.

Generally, 'epoxy resins' (amine based) do not melt or soften styrene based foams.......but, `always best to check out the product data-sheets for the resin system you have in mind......or a quick call to the manufacturers/agents might be a good idea.

The 'foam in a can' expanding urethane (gap-sealer) foams would be resistant to most-all styrene esters and once cured could be easily carved/sanded before coating with resin......You might find that the nozzle might produce irregular shapes close to the rock effect you seek.

However, the two 'issues' that 'really' come to mind using foam and resin in your application are; buoyancy and toxicity.

 

[busastars]

Thanks Debs, Ive read on people useing the foam in a can to do the rocks etc, this is the whole backround, already carved it all out, build it up, just going back into the shed now with the propaine gun to mould it all in.

One thing I have noticed is one the polystyrene has been heated up it seams to go hard, ive had a little play with a sample piece.

Thats the thing as its for fish is the toxins, Ive read that resin once cured is inhert and not toxic but will look for a marine epoxy resin.

This is the Resin I have in mind:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=260468069780&ssPageName=STRK:MEWAX:IT


If I can get away with just paint and Resin then thats one last thing to worry about with cement as this pushes up the PH level if I do miss any spots.

 

[Debs.]

Thanks Debs, Ive read on people useing the foam in a can to do the rocks etc, this is the whole backround, already carved it all out, build it up, just going back into the shed now with the propaine gun to mould it all in.

One thing I have noticed is one the polystyrene has been heated up it seams to go hard, ive had a little play with a sample piece.

Thats the thing as its for fish is the toxins, Ive read that resin once cured is inhert and not toxic but will look for a marine epoxy resin.

This is the Resin I have in mind:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=260468069780&ssPageName=STRK:MEWAX:IT


If I can get away with just paint and Resin then thats one last thing to worry about with cement as this pushes up the PH level if I do miss any spots.

Marine resin systems generally are not hygroscopic; with water absorbtion being a common issue with commercial polyester-matrix composites.

Whilst generally considered 'inert' when cured; the actual 'cure cycle' can be quite prolonged, even running into many-weeks (hence the characteristic aroma of recently manufactured glassfibre items) and it is during this 'green' time that I`d assert that any toxicity is a risk for your fish......there are catalyst 'cure-accelerants' which may cut down the curing 'green-time' to an acceptable time.
......product data sheets are your friend!

Of the two conventional Polyester catalysts: Methyl Ethyl Keytone Peroxide (MEKP) is considered to be of a higher toxicity than Benzoyl Peroxide.

 

[busastars]

Just got back in from the shed, had the propane torch on the polystyrene, before everyone tells me I know its flamable, haha, backround is nice and hard but does feal a little brittle, it realy does look the buisness, I want to try and get away with using cement now and go with just paint & Resin.

So the answer on cure time is read the lable.

One other thing, Paint. I know its going to be sealed with the Resin but I still want to take precausions, been reading and the concensiss seams to be use Acrylic paint.

Ive looked in the Range and Acrylic paint is expensive for small amounts, as in the Artistic type.

I noticed other paints have Acrylic in them, is there any way of telling if I can use emulsion / car spray / somthing else non toxic? Ive had a read on some Emulsion paint and carnt see a thing stated on them.


Quick couple of pics:

 

[penfold]

The applied resin is not going to get hot enough to bother the foam, the heat build-up issues only occur where you have a lot of resin in one place i.e. the mixing pot; mixing large quantities(litres at a time) at once can start fires and/or melt plastic mixing buckets, especially if you've overdone the catalyst. If you're really worried, mix a small amount and try it. The resin you've picked will be fine but it's a bit pricey, especially with the postage; do you have anywhere local you can buy the stuff? My local purveyor would do 5kg of resin for 15 beer tokens. If the resin turns out to attack/melt the foam, I'd construct a barrier coat out of papier mache to put the grp over. Using epoxy would be an expensive way of avoiding this, it's about 8 times the price!

As far as poisoning your fish, get the catalyst ratio right so the resin sets properly, then let the styrene(solvent carrier in the resin that causes the pong) evaporate for 2-3 weeks before painting. I'd have thought most domestic paint had to be fairly non-toxic given that it has to be proof against anklebiters gnawing on it, so maybe try ordinary gloss.

Out of interest, how are you going to stop it floating away; all that foam must have a fair bit of bouyancy?

 

[Debs.]

`Very nice carving job busastars; I can see it`s going to look really-smashing when coated and painted.

 

[Pete.]

I'm sure I read somewhere of using artex or plaster over a polystyrene mould to prevent fibreglass resin from melting it.

 

[Normsthename]

So I was just wondering would a mix of resin melt polystyrene?

I used to be a GRP Laminator many years ago, resin will melt polystyrene faster than you can say "What the F....."

Andy

 

[busastars]

Ive read on a few sites now where people have used just resin over the polystyrene, I will plan on doing a light coat first, the polystyrene will be painted first then the resin on after.

If I do a test piece and it dont work I gess I will have to cement and skim the surface first.

To stop it floating away I will use fish tank silicone all over the back & sides.

I should be able to let it cure for a couple of weeks tops as I got to re'house the fish for a short while. I know if I went the cement route and used G4 pond sealer I could have it done in no time BUT G4 sealer will cost me way over £40.

 

[oz.]

Whenever i mix resin it's always in a metal tin - quite shallow but nice and wide. Also the scraper/mixer that comes in the resin kit goes straight to the bin and out comes the tin snips and 1mm sheet ali.The resin tends to dissolve most plastics some faster than others, this is how they get such a good bond to the material.

 

[pedrobedro]

I mix polyester resin in polythene plastic kitchen measuring jugs from Wilko. They only cost pence and when the resin sets you can flex them so it cracks off cleanly and you can use them repeatedly. I also use talcum powder to dust the surface after the resin goes off as it stays tacky. Have a look on CFSnet for hints on using glass and resin. For making moulds you can use insulation batts in place of polystyrene, the big pink or blue slabs you see on building sites.

 

[oz.]

There is someone on the 205gtidrivers.com forum using polystyrene to make molds for fiberglass and carbon fiber. He sprays on some kind of gelling agent which protects the poly from any resin

 

[busastars]

I think with me doing a couple of coats of emulsion that this should aid the poly from the Resin.

Soon see, ill do a test piece first and then update

 

[busastars]

Quick question, got me Resin & Catalyst today BUT no instructions on what ratio to use. Anyone got any suggestions???????

 

[Normsthename]

This should get you started

http://www.cfsnet.co.uk/acatalog/Web_FibreglassGuide.pdf

Andy

 

[busastars]

Thanks all sorted now.

Just a quick update, ive done two coats of paint & resin. The resin did shrink and slightly hole hear and there. Got it all stuck in tonight but not 100% impresed yet look close and you can see the imprefections.

Maybe once there is water, light etc etc it will look better. It is darker than in the pics.

Also I cant see it not lotting water behind so hopefully it will be all ok once cured.

 

[Debs.]

`Lovely job; I really think that`s going to make a super scene when the water, plants and fish are in!