Casting with Fiberglass Resin?

[Flintlock]

I've done some polyurethane resin casting, but I am impressed at the quality of fiberglass casting I've seen a few people do. Trouble for me is - I can't find much about how to do it on the internet. How is the process the same/different from resin? Where do you get the fiberglass from? Is it more or less expensive than typical casting resin? Could someone point me in the right direction for information? Thanks!

 

[Jedi Dade]

Drop REL a note and he will probably give you the info you need.

Basically its a 2 part epoxy that works with the glass matting for fiberglass work. you mix it up and pour, lay in some glass matting (Im not sure if the matting is "completely" necessary) then wait... In short though it taks a long time for the stuff to fully cure... and its pretty "Fumy" so do it outside of the house... in a well ventilated area...

I'm pretty sure that you can use the same RTV silicone molds that you use for ployurethane resin.

Jedi Dade

 

[Rats]

Flint, most hardware shops in Aus have the fibreglass resin for sale. Either as kits or individual components. I'm sure the US would be the same. The other place to look is ships chandlers (boating supply shops).
It's usually a two part mix, but only a few drops of catalyst into a biggish volume of resin/glass. Instructions are normally printed on the side of the can/container and are not hard to follow. The catalyst is commonly MEKP, an organic peroxide, and is VERY nasty stuff. Skin irritant and makes you blind if you get it in your eyes.
Having said all that, as long as you wear the normal safety gear it's easy enough to deal with. Fibreglass stuff is relatively cheap and it is useful to get some chopped mat or woven cloth to help strengthen the parts. Neat fibreglass is quite brittle. I'm sure you can use it in RTV moulds, but I haven't actually tried myself, so don't know if it damages the mould or not.
Have fun, get a small kit from the hardware shop and give it a go!
Cheers, JT

 

[James Kenobi 1138]

.

 

[REL]

The type of fiberglass that stinks is polyester, plus it shrinks a lot. Epoxy has no odor to speak of and is a lot less toxic, that's what I use.

Polyester doesn't do well in tin based molds unless you spray in primer, or use platinum silicone, whereas epoxy behaves about like resin in a mold.

Epoxy is more durable, has virtually no shrinkage, and isn't nearly as brittle as polyester.

Of course epoxy is more expensive, and has an exact mix ration between the A and B components. Where poly there's a little leeway.

I get my epoxy fiberglass here
http://uscomposites.com/epoxy.html

And the fabric here

http://uscomposites.com/cloth.html

Depending on what the application is will depend on the cure time you'll need. For clear castings you'll have to use the slow set. If clear isn't an issue you can use the faster curing epoxy.


To lay up the fiberglass, powder/mold release your mold, brush in a skin coat, let it nearly cure, or completely cure it doesn't matter, then cut you fabric or matt place it in the mold on top of the skin coat, and using a chip brush wet it out. It's basically like papermache.

You want more fabric than resin, that's where you get the strength.

 

[Nwerke]

The type of fiberglass that stinks is polyester, plus it shrinks a lot. Epoxy has no odor to speak of and is a lot less toxic, that's what I use.

It's still toxic though. The reaction can be sudden and brutal. As Dade said, do it outdoors.

Epoxy is more durable, has virtually no shrinkage, and isn't nearly as brittle as polyester.

Amen. Much easier and nicer to work with.

Of course epoxy is more expensive, and has an exact mix ration between the A and B components. Where poly there's a little leeway.

It's often 50/50 though, which is hard to cock up!

To lay up the fiberglass, powder/mold release your mold, brush in a skin coat, let it nearly cure, or completely cure it doesn't matter, then cut you fabric or matt place it in the mold on top of the skin coat, and using a chip brush wet it out. It's basically like papermache.

Nobody's mentioned gelcoat yet. With polyester, you need to lay in gelcoat first off, it's basically just a thicker, coloured mix of polyester resin. You wait for that to mostly cure then go on with your laminating using normal polyester. It's a pain in the butt but normal PE resin will pool and not cover the whole mould surface, so you need the gelcoat to kick off with.

This is the other nice thing about epoxy: you don't need it, just do what REL says.

Have a good supply of cheap brushes handy, you'll be throwing most of them away after one use.

Cheers,
Martyn

PS can't speak for the States, but here epoxy is a bit cheaper than PU resin. It may mean less work and expense creating moulds, since you'll often only want an open, half mould. That said each individual glass layup is more work than pouring PU.

 

[JPolacchi]

If you check out the Tap Plastics web site,I believe they have online tutorials or you can request help?Epoxy is toxic though,maybe not as far as odor/vapors go, but you can develope a very high sensitivity to it.Its always important to "glove up" when laying fiberglass and resin.

 

[Flintlock]

Everyone, thanks for the tips! You have all been very helpful, and this info will be very, very useful to me in the near future.

 

[Dougie Fett]

Everyone, thanks for the tips! You have all been very helpful, and this info will be very, very useful to me in the near future.

Likewise, thanks guys!

 

[Trap Joe]

Quote:Nobody's mentioned gelcoat yet. With polyester, you need to lay in gelcoat first off, it's basically just a thicker, coloured mix of polyester resin. You wait for that to mostly cure then go on with your laminating using normal polyester. It's a pain in the butt but normal PE resin will pool and not cover the whole mould surface, so you need the gelcoat to kick off with.


Or instead of gelcoat, you can fill the polyester with glasspowder.

 

[jedistine]

here's some info on the differant types of resin from the place I use.
http://www.fibreglast.com/contentpages-About+Polyester+Resins-33.html

 

[Nwerke]

Or instead of gelcoat, you can fill the polyester with glasspowder.

I've only used that to lighten a casting. Never thought of using it that way. What kind of surface do you get?

 

[Trap Joe]

I've only used that to lighten a casting. Never thought of using it that way. What kind of surface do you get?

Like gelcoat. A very good, detailed one.

 

[JPolacchi]

I wouldn't use gel coat,it shrinkis too much unless the shrinkage doesn't bother you?Be better off doing a slush mold with urethane resin,build up a shell, then lay in epoxy&glass.

 

[exoray]

I wouldn't use gel coat,it shrinkis too much unless the shrinkage doesn't bother you?Be better off doing a slush mold with urethane resin,build up a shell, then lay in epoxy&glass.

Yeah gelcoat is hard for the hobbiest to do, not saying it can't be done but it's certainly harder then urethane resins...

On that note, you need to do some test before you commit, not all urethane resins are the same and not all layup resins be it epoxy or polyester are the same, I have experienced delamination issues between certain combinations of urethane layers and fiberglass resin layups...

Just a word of advise, if you venture down that road, it's my preferred method and achieves great results right out of the mold, great finish surface...

 

[star-art]

Just curious, does anyone combine polyurethane resin and glass fiber? Or, is that what you just posted? I understand the idea of starting with a layer of PU resin, then switching to epoxy and glass. But, I don't recall hearing about anyone just adding glass to strengthen a polyurethane casting.

 

[Trap Joe]

I do this sometimes. It workes fine - if the shape of the cast holds the polyester/fibers all around.

 

[exoray]

Just curious, does anyone combine polyurethane resin and glass fiber?

It should work fine but you probably would want to get a slower casting resin as the normal 2-3 minute time won't give you much time to get complete wet out of the fibers... Also you would have to check the fiberglass to make sure it was compatible, even some mats are not compatible with epoxy as they use a binding agent that dissolves in polyester but doesn't in epoxy creating an incomplete wet out...

That shell is a urethane detail coat backed up by a custom blended fillet material and then backed with polyester fiberglass... It works quite well but I did originally have delamination issues that was cured with trial and error testing of different products...

 

[oujala]

About how many layers of fiber in that proton pack?

 

[exoray]

About how many layers of fiber in that proton pack?

One good solid layer of 1.5 oz mat, probably 2 layers in the end by the time its overlapped, the fillet and detail material also has reinforcement, so it's not "traditional" fiberglassing... Because of the application, size and shape there was no need to do any more fiberglassing or get crazy, I can stand on these shell and jump up and down without any damage and minimal flex...