Casting in GRP or P

[seaesta]

Encouraged by the recent debate about casting rubber I would like to ask if anyone has successfully cast in fibreglass resin? I have tried to make a few bits but failed due the brittle nature of the final product and fractures due to excess heat generated by the exothermic reaction. Has anyone found a way to cast in GRP i.e. to include the fibres in a pourable mix and make a durable cast that is reasonably close to a molded object?

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[PuffTheMagicDragon]

Use cut fibres of around 20mm. Mix well into uncatalysed resin. Resin ratio approx 2 glass to 1 resin, by weight. Add catalyst for a v-e-r-y slow cure i.e. < 1%. Pour slowly into cavity, tamping down with a lolly stick, so that any air bubbles can float off. Take your time over it and you should be all right. You do not say what items you wish to mould: beware if you make such things as cleats or similar as the molding might not take a shear loading.
Fair Winds!


<hr width=100% size=1>Wally

 

[snowleopard]

you can buy microfibres, length about 3mm. they are effective but nasty to work with as they are prickly.

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[oldsaltoz]

G'day Martin,

You can purchase epoxy or standard resins designed to do just this.

They come in range from clear to cocktails to perform all manner of tasks, contact any resin manufacturer and they will send you heaps of information.

I hope this helps...


<hr width=100% size=1> Old Salt Oz /forums/images/icons/cool.gif Growing old is unavoidable. However, growing up is still optional.

 

[Avocet]

I used to use chopped strands about 6mm long and found these to be good for most applications. Depending on the size of the mould, heat will nearly always be a problem, though. Try using as little catalyst as possible (but not less than the manufacturer recommends as a minimum) and make sure you put it somewhere cold until it has reached it's peak temperature. A friend of mine put some in the freezer and said it worked quite well but his wife then told my wife that she had to throw out the entire contents of said freezer because everything tasted of styrene! On the whole, laminating resin isn't designed for casting - as has been suggested, best look for casting resins.

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