Old Epoxy Won’t Stick

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Old Epoxy Won’t Stick appeared first on Hardware for Creative Finishes

Here’s what I thought was interesting. Titled “Old Epoxy Weird Behavior”. It’s not actually a wood question but it’s about glues. This is by REAL Old Nick.

I want to stick some Velcro and webbing strap to corflute board. My first attempt resulted in a complete failure. The glue simply came away from the corflute. So I punched lots of tiny holes in the corflute for a key and tried again. The result was that the epoxy stayed in the keyed corflute but it failed to adhere to the back of the Velcro. Clean as a whistle. That surprised me as Velcro is a woven-looking material and I thought that would be okay. And though it adhered to the strap and the corflute, it simply tore when I pulled up the strap leaving a residue on both strap and plastic.

The stuff is very old. 10 years, probably more. It works fine, mixes okay, and sets well, it just seems spectacularly weak and not sticky. Has anyone tried this or have used old epoxy before, not of this breed, but had no trouble?

One suggestion, corflute is made from polyethylene HDPE or LDPE in solid blocks and it makes reasonable bearings but very few things will stick to it, unless you don’t want them to. He’s a bit sarcastic. Most Velcro-type products also made from slippery plastics like nylon HDPE. So it’s no wonder you had to go to extremes to get the preparation and application. I’m a bit surprised you didn’t just get a peeling off every time instead of some stick and the glue fail.

As for the glue fail, many things have been marked as epoxy glue over the years and only some of it is the real thing. If it is actually a polyester-based resin with a filler and MEK catalyst as the “B” Part, the MEK could have partly evaporated, which means it won’t be setting to full strength. Some polyurethane curing agents also have a definite shelf life due to internal chemical reactions or evaporations. And some real epoxies are just plain very sensitive to the correct amount of curing agent often in the range of 1/100^th of a gram or less for some specialist formulations.

Basically if the glue fails, use it to repair broken pot plants or something non-critical and get a new lot of epoxy from a reliable company like Selleys, BoteCote or West, which are formulated for people like you and me.

Another suggestion is to use contact cement. That’s a very good idea because you can glue it onto both surfaces and when it is tacky, you join them together.

Another reply from the original question was, I was not surprised by the initial un-keyed failure. I could see the plastic was going to be a tough cookie. When the glue basically disintegrated, that was a surprise. Interesting about the Velcro, I could see how it was a slippery plastic but it looks as if the weave or grain was expected to take. I’m not sure about that. It has like oily plastic on it sometimes. I did not know about dodgy epoxies. I doubt this is polyester as it worked well in the past and polyester is never a good adhesive. So in my limited experience with epoxy, you don’t use it to join pieces of material together for like signs and things and contact cement is much better at that. It makes a much better bond. You can put it on both surfaces and lather it all out and sit it there until it gets nice and tacky and then join it back together. Whereas epoxy, well, it’s designed to fix boats and things that are rough and got plenty of surface area on them I suppose. So yeah, an interesting little post.

http://www.woodworkforums.com/f198/old-epoxy-weird-behaviour-170804/?highlight=question

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