Looking for a faster curing epoxy.

I used Bob Smith 15 minute for at least 5 years. Did have a few failures come back, but a dishwasher was usually involved. I've since switched to Blade Bond 15 minute, then to G Flex. Can't say I can tell much difference. On the G-flex, I set it in front of my small electric heater, or put it outside in the sun. Cuts the time down to three hours. Not that big a deal if you plan for it in advance. I typically will hand sand a blade and glue up the handles first thing, then while it's curing, I'll hand sand the next one and glue it up, and so on. Just find something productive to do while the glue cures.
 
One thing that always gives me pause in this debate is water-resistance. If you have a mechanical fastener, then a quick cure epoxy is probably more than sufficient for strength. However, its primary function in this scenario is as a sealant, and quick cure epoxies are only ever WATER RESISTANT, not WATER PROOF (which the 24-hour cure ones, like G-flex, are). Since I make kitchen knives almost exclusively, I want the most water proof epoxy I can find. So, is there a truly water proof quick cure adhesive? If so, I will be a very happy man. Especially, I would love some kind of water proof CA, etc, that's thin enough to wick into the micro gaps between bolster, blade, and handle. Solder would probably work, but I use copper for my bolsters primarily, and I have heard about corrosion issues when you create an electrically conductive bond between copper and steel.
 
1) Water resistance.
All two part epoxies are waterproof. For any practical purposes they absorb no water, do not de-polymerize by extended water immersion, and do not change their phisical properties.
2) Physical strength.
Slow reaction time yield a better overall polymerization and cross linking. Fast epoxies are weaker. The distinction is academical only, though, since even the weaker epoxies will be stronger than the adhesion to the wood/metal.
3) Adhesion is the weak link, then wood.
Metal-epoxy-wood bonds will rarely fail on the epoxy. Unless the metal is well prepared (corse sand blasting, holes) the adhesion will fail there. Next, the wood itself will give.
4) Viscosity affects wood penetration.
Thinner epoxies, on most wood, will penetrate better. In this regard, fast epoxies are at a disadvantage since they are usually thicker.
5) Temperature is everything.
I use the west systems 105 with the fast curing agent. It gives me 15 to 30 minutes of work time, with a nominal hardening time of 8 hours. But you can heat it up to 65C, and that will bring down the hardening time to 1h.
 
This is far from scientific, but I always see that only the slow-cure epoxies are actually listed as being waterproof. For example, if you look at Bob Smith Industries' website, you'll find that their quick cure is not recommended for long term immersion in water; their medium cure is listed as "more water resistant"; and their slow cure is the only one they say is waterproof.
 
I’ve been on the Acraglas boat from the beginning. Never had a problem with it. If it’s good enough for custom bedding a large caliber rifle with enough recoil to put ya on your back, hold tight groups, time tested in all environments then it’s good enough for my knives. And you can still get big bottle!
 
One thing I failed to consider was shelf life of a given epoxy. Anybody know the shelf life of G Flex?
 
Tenebr0s said:
This is far from scientific, but I always see that only the slow-cure epoxies are actually listed as being waterproof. For example, if you look at Bob Smith Industries' website, you'll find that their quick cure is not recommended for long term immersion in water; their medium cure is listed as "more water resistant"; and their slow cure is the only one they say is waterproof.
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The note mentions boats.
That formula in particular has plasticizers added. That probably makes the cured mix slightly more water permeable, and a worse option for waterproofing wood. I don't think the epoxy itself will weaken much by immersion.
 
For full tang knives, I often use gorilla polyester glue. It sets enough to work on the knife in two hours. It’s great for gluing liners to scales as well. When I do g-10 guards, I use 5 min j-b kwik. It dries perfectly black, matching the guard. Full tang knives get 24h West Systems epoxy usually I have done quite a few with 6h j-b weld. Zero have come back.
 
gammarad said:
1) Water resistance.
All two part epoxies are waterproof. For any practical purposes they absorb no water, do not de-polymerize by extended water immersion, and do not change their phisical properties.
2) Physical strength.
Slow reaction time yield a better overall polymerization and cross linking. Fast epoxies are weaker. The distinction is academical only, though, since even the weaker epoxies will be stronger than the adhesion to the wood/metal.
3) Adhesion is the weak link, then wood.
Metal-epoxy-wood bonds will rarely fail on the epoxy. Unless the metal is well prepared (corse sand blasting, holes) the adhesion will fail there. Next, the wood itself will give.
4) Viscosity affects wood penetration.
Thinner epoxies, on most wood, will penetrate better. In this regard, fast epoxies are at a disadvantage since they are usually thicker.
5) Temperature is everything.
I use the west systems 105 with the fast curing agent. It gives me 15 to 30 minutes of work time, with a nominal hardening time of 8 hours. But you can heat it up to 65C, and that will bring down the hardening time to 1h.
Click to expand...
Also, in my experience at my day job (which is not knife making), the glass transition temperature (the temp where it goes rubbery) of epoxy is strongly correlated to the curing temperature (so curing at higher temps, within boundaries, ensures it doesn't go rubbery at low temps).
In the high precision instruments we develop, moisture absorption can play a significant role in stability. I can imagine this might also cause additional stress when used in knives when the glue bond tries to swell but the knife and handle parts don't. But this is speculation on my part, no hands-on experience.
 
There was a thread about a few who were using a two part adhesive where you put a hardener on one side and the adhesive on the other and they set in just a few minutes. I don't remember what the product was but had planned to look it up and get some when I start running low on g-flex.
 
Bond time VS Cure rate
K&G 24 is the best I ever used. Tested it and destroyed the knife throwing it into a tree Handle finally broke the Epoxy stayed put with shards of the handle attached. BTW if I remember correctly even Superglues bond instantly but take actual 24hrs to cure
Fast or forever is a good guideline
 
1
Hankins said:
Bond time VS Cure rate
K&G 24 is the best I ever used. Tested it and destroyed the knife throwing it into a tree Handle finally broke the Epoxy stayed put with shards of the handle attached. BTW if I remember correctly even Superglues bond instantly but take actual 24hrs to cure
Fast or forever is a good guideline
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2P-10 glue Cures in 5 minutes and if you use the spray activator it cures in 30 seconds... As indicated on the product labels
 
Bob Duguay said:
Been using G-Flex with no issues but sometime I just don’t want to wait 24 hrs to get back on the knife. Is there a strong 3 hr epoxy that you guys can recommend?
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For materials that can take the heat Permabond single part epoxy fully cures in 75 minutes at 130°C and claims exceptional strength and toughness.
 
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