Epoxy woes

[sjurba]

Been tinkering with a speargun project,laminating teak with epoxy and woven glassfibre cloth between the laminates,but it seems not to bond properly,anybody got an idea why it comes apart? Its been abit cold in the workshop,maybe as low as zero degrees celcius during the curing process could this be the reason?

 

[l_smircic]

Been tinkering with a speargun project,laminating teak with epoxy and woven glassfibre cloth between the laminates,but it seems not to bond properly,anybody got an idea why it comes apart? Its been abit cold in the workshop,maybe as low as zero degrees celcius during the curing process could this be the reason?

Were you using expoy or something else to bond this ?

 

[sjurba]

yes, two component epoxy, same make as the woven glassfibre cloth,used it before to laminate wood without any problems.

 

[cdavis]

Teak has a lot of oil in it. If you don't remove it from the surface with some solvent, most glues, epoxy, paint, etc won't stick.

 

[foxfish]

You need to buy purpose fiberglass materials designed to bond with epoxy as many fiberglass matings have impregnated styrene to enable the separation of individual fibers when working with polyester resins.
Why are you using the fiberglass anyway?

 

[sjurba]

I rubbed the teak with 40 grit sandpaper and wiped it over with acetone before laminating.The fibreglass cloth is of the same make as the epoxy and sold to use with this epoxy,I was planning a slim speargun and figured some fiberglass would add strenght to the "spine" of the gun.

 

[foxfish]

In that case I have no answers only guesses, epoxy out of date perhaps or not accurately mixed, high humidity?
I have seen guns with carbon fiber sandwiched between the laminate but personally I think that it is about being cool rather that strength.
If you want strength then a carbon wrap around the outside will do that but flat layers of fiberglass or carbon will not any significant strength in my opinion - nothing wrong with cool though!

 

[cdavis]

acetone wipe should take care of the oil issue, especially at first.

Looking at your first post, zero C is pretty cold. Epoxy will take a very long time to set at that temp and some types might not set at all. How long are was the bond clamped before you tried it? Do you know what the recommended temp range is for that epoxy?

Connor

 

[hteas]

The cold and damp can have a really big effect on epoxy. I have worked with it for a lot of years, and Alaska, like Norway, has a lot of cold damp weather that simply does not allow the epoxy to cure properly. My only suggestion is to wait until that one really nice day next summer. Adding extra catalyst doesn't seem to help, like it would for polyester resin.

 

[foreign]

How ight are you clamping? Possible dry joints? Just thougts

 

[s14slide]

I'm pretty familiar with composites. I've built competition glass and carbon/kevlar gliders. I'm 100% positive its your temps. I don't know of (doesn't mean it doesn't exist) an epoxy that will cure at that temp. You should be looking at a minimum 65F. 90's to low 100's is ideal. Depends on resin. Make sure to preheat your wood before you try to strip the oil too. The wood pores will expand in the heat and allow more oil to the surface. If you have a really cold environment, make a hotbox. 1" or so foam insulation with the aluminum backing works great. Aluminum side on the inside. Heat it with a lightbulb or two and a computer fan. Anything to circulate the air. Use a food thermometer (digi is best) to monitor the temp.

For strength, nothing beats a vacuum bag and heat, but now your investing money. But heat and compression are your keys to a proper bond, thus resulting in strength. A tip is to cut up a bicycle innertube or two, cut into long 1" strips and rubber cement the ends together. Lay glass, a separation layer, then spiral wrap with the rubber as tight as you can. Insert in oven and cook until golden brown or a toothpick comes out clean.

Now that I've writtten all of this, I realize its summer already. Maybe it'll help some future builder.

Sent from my craptacular not-so-smart phone.