Resin cured and its sticky??? What i do wrong?

[Meathead316]

Hi

Ive been wanting to have a play with fibreglass resin for a while now so i bought a small tin and some hardener from halfords (car parts store in uk) along with a decent respirator.

I got home, mixed the 2 parts as per instructions and coated a test piece (cardboard) on the inside and out.

2 hours went by (box says cure time 20-30 mins) and its not wet, but its sticky and if i touch it leaves finger prints... The bit left in the bottom of the cup (about 2cm worth) has gone rock solid so im sure its set... Why is it sticky? I cant sand or paint it like this.

Im thinking its either i got ratios wrong, or coz its outside and its cold and damp has ruined it.

Can someone please shed some light on this please

Thanks

 

[Murdoch]

Is it sticky or is it tacky. If it's tacky then sand it. The piece should be fine after that...GM

 

[gyoung2993]

may have not been enough harderner , with the quanity of resin, cause it usually gets hot and tihckens until its cured, too much hardener and it will really get hot....JMO

 

[Charliefox]

The stuff left in the pot gas gone off because im assuming its thicker, the way fibreglass resin sets is through the heat produced by the chemical reaction, because the stuff left in the pot is a thicker layer irs produced more heat and so gone off faster. Try putting your cardboard in an up turned cardboard box and cut a hole for a hairdryer or heater, and another hole opposite to let some hot air out, hey presto mini oven without sticking resin anywhere you have food! Hope that helps, if im just doung thin layers i tend to over catalyse, particularlly when the weather is cold, just be careful i have seen someone set fire to a bucket of resin from trying to make it go off super quick!

 

[Fly4v]

Sounds like the hardener and resin wasn't completely mixed.
You can try rubbing hardener on what you coated to see if it will harden.
Toss it in the oven...place it in the sun...
Or just wait to see if it will eventually cure.

Some epoxy will have a waxy feeling when cured. It will gum up sandpaper so I wash it will dish soap and hot water and this cuts it enough so I can start sanding.

Also, a larger volume of resin will cure faster than a thinner coating because of the heat generated.
I have had resin melt plastic cups

 

[Meathead316]

Aaahhh so it generates heat to cure... Well right now outside is about refigerator temp... Guess thats not helping, im gonna try the cardboard box hairdryer oven idea. Update to follow...

Ps

Whats the difference between sticky and tacky?

 

[Meathead316]

Oven worked! Its now really smooth (like glass) but it appears to be quite brittle... Can i do another coat of resin straight ontop? Will it stick? Will i need to sand first?

 

[bigjustin12]

I would think that if it is TOO hot in the box then the resin might cure too fast. It would make sense that it could be brittle then. Just as if you used too much hardener.

 

[Lflank]

When that happens it's usually because there either wasn't enough hardener or it didn't get mixed enough to catalyze all the resin. But if the stuff in the cup is OK and the stuff that was outside isn't, I'd suspect that it was just too cold for the catalyzer to work properly. Need to find a warmer place to work.

 

[Meathead316]

What should it be like once cured. Say i got a flat piece of card and gave it one coat front and back, let it cure. What shud it be like. Say i try bending it in half, shoul it just bend or crack or what?

 

[Lflank]

What should it be like once cured. Say i got a flat piece of card and gave it one coat front and back, let it cure. What shud it be like. Say i try bending it in half, shoul it just bend or crack or what?

It's pretty stiff stuff, so it'll definitely crack if you bend it too far. It's not for pieces you want to be flexible. It ends up like a thin sheet of plastic.

If you want flexible pieces, you're best off making them from foamie instead.

 

[Meathead316]

I dont want flexible, but i dont want brittle either. Its for armour, can you imagine sitting down wearing resin thighs, them cracking and breaking and sharp shards up your ass?!

I have just ordered some polyurethane resin from ebay, hopefully its less brittle.

It shud be here by friday, the only pieces of armour i have left to build is hands, head and half a foot

 

[Drack]

Couple of questions if I may. First what GSM card are you using or are you using cardboard box card? Second are you fibre glassing the pieces on the inside because if all you are doing is a couple of coats of resin then yes it won't be strong enough for anything but display. When making armour you cut and glue around 225-250GSM card, coat it inside and out with resin (for some stability and if your piece isn't as perfectly shaped as you want you can heat gun and push it into a better shape), fibre glass or "rondo" the inside then use filler on the outside for your detailing. If you already knew this then sorry but I assume you didn't as you would know the answers to your problems. So to help you on your way watch these videos Here. Hope this helps out

Tom.

 

[msleeper]

I dont want flexible, but i dont want brittle either. Its for armour, can you imagine sitting down wearing resin thighs, them cracking and breaking and sharp shards up your ass?!

That's the thing about hard armor. You don't sit in it.

 

[Lflank]

That's the thing about hard armor. You don't sit in it.

Or you make the butt plate out of foamie and leave the rest stiff.

 

[Charliefox]

What gives fibreglass its strength is the glass matting, the resin by itself is naturally brittle. Just a thought if you didnt want to use glass mat, howabout a fabric with resin? Something natural with a fairly loose weave and heavy thickness would probrably do the trick, you want the resin to soak in not sit on the surface. Glad the box oven worked good luck!

 

[Lflank]

Couple of questions if I may. First what GSM card are you using or are you using cardboard box card? Second are you fibre glassing the pieces on the inside because if all you are doing is a couple of coats of resin then yes it won't be strong enough for anything but display. When making armour you cut and glue around 225-250GSM card, coat it inside and out with resin (for some stability and if your piece isn't as perfectly shaped as you want you can heat gun and push it into a better shape), fibre glass or "rondo" the inside then use filler on the outside for your detailing. If you already knew this then sorry but I assume you didn't as you would know the answers to your problems. So to help you on your way watch these videos Here. Hope this helps out

Tom.

The fiberglass cloth/bondo process does make very strong, very stiff armor.

I make my pep stuff with just the resin, no fiberglass cloth. It's not as strong or as stiff.

 

[archytekt]

Depending on the type of resin you used it might be normal to be tacky when cured. This has to do with the fact that some resins contain wax and some don't.

Oven worked! Its now really smooth (like glass) but it appears to be quite brittle... Can i do another coat of resin straight ontop? Will it stick? Will i need to sand first?

So if you want a 2nd layer of resin, why did you oven it? It would be preferable to have it still tacky for the two layers to achieve a better chemical bond.
You should read some stuff on fiber-glassing.

 

[Meathead316]

Ah man i didnt really wanna have to use fibre glass...

Thanks for the info, ill wait for my polyurethane resin (casting resin) gets here and have a play. This stuff shud be easier to mix as its 50/50 ratio

The card im using is corrugated (pizza boxes)

You cant sit on cosplay solid armour ....

Lets be real, im probably gonna try using fibreglass regardless of how just resin turns out ( for future referance) Couple of questions if i may, what thickness matt will i need? How many layers? Do you apply it in large sections? Or lots of small over lapping pieces (like paper mache)

One last thing about fibreglass, safety related so very important. Can i handle the matt with bare hands, or will i get splinters or something? (Hope not, i hate wearing gloves for fiddly stuff)

Thanks

 

[Drack]

I am not sure about the thickness of the mats as just bought a pack and didn't read its thickness (don't think it really matters as long as its not too thick). You can do the fibre glassing with out gloves but its a big messy affair so you don't want to not use them really. It's not that fiddly really, you want cut out squares around 60-80mm and do 2 layers of them. Try to avoid the detailed areas at first cause as you lay them you will soon get a feel of how to do it and then you can start dropping some smaller pieces into the detailed areas as there will be resin every where .

Do a thin layer of resin, pop your mat on then paint another layer of resin on top. Let it dry and repeat. Obviously the more layers you do the stronger it is but the heavier the piece. You can get away with one layer mat on the parts that won't have any strain on them but make sure you over lap the mats a bit. The more pieces you can do thin layers on the better so you can keep the over all weight down.

I would highly recommend not using corrugated card cause in my opinion this adds weakness to your pieces. I have seen people use it fine but it just doesn't seem right to me as no matter how much you fibre glass the inside you will still have a weak foundation for your body filler layer on the outside. One bad knock and its gunna break/crumble away.