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Is Epoxy a Good Bonding Agent and Where Is Weldwood Plastic Resin Glue
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Q: Years ago, in school shop, we used to work with something called Plastic Resin glue, made by Weldwood® and others, that was a urea-formaldehyde formulation (brown powder) you mixed with water to produce amazingly strong joints. I’ve been searching for it lately, and it seems to have disappeared from the shelves. Has it been pulled because of new regulations or simply replaced with something that’s significantly better?

Also, I read more and more about the usage of epoxies for bonding wood, yet I also remember reading that experts agree that epoxy is not the best glue for wood because it depends on surface adhesion, rather than actual penetration, and it tends to produce a joint that is not as strong as one might think. Can you comment on this, too?

Epoxy wood glue Epoxy is a fine wood adhesive if you're willing to get over the smell and visible glue lines, just use epoxy with as long an open time as possible for the tightest bond.

A: I know the product you are talking about and have used it from time to time. I did a Google search and found that Weldwood, made by DAP, is still around and it is still for sale. As to the question about epoxy as a less-than-desirable bonding agent: I have never personally seen a well-made joint fail when it was bonded with epoxy. For me, its main drawbacks as a day-to-day wood glue are many: it’s expensive, it’s putzy to use, it’s messy, it leaves very visible glue lines, and it’s kinda stinky. But I have no argument with its capabilities to bond two pieces of wood together. With that said, I recommend using an epoxy with a long open time in wood-to-wood operations, because those formulations are slightly more elastic when they cure.

Of course, epoxy’s primary benefit is its durable waterproof nature. Boat makers have used it for years and in a type of construction where glue joint failure is not acceptable.

Image #1: Applying epoxy
Image #1 Original Caption: Epoxy is available in formulations with open times ranging from 5 minutes to overnight. If you are planning to use epoxy for wood-to-wood joinery, use a product with as long an open time as is practical.

posted on December 1, 2010 by Rob Johnstone
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One thought on “Is Epoxy a Good Bonding Agent and Where Is Weldwood Plastic Resin Glue”

  • John Stricklin

    I want to coat a curved surface (plastic substrate, not polyethylene, and normally provides good bond with epoxy) with contact cement to adhere a strip of wood then coat the whole surface with epoxy -- there will be a significant area of exposed contact cement on each side of the wood strip and in this area I am concerned about compatibility -- will the epoxy "eat" through the contact cement and give good adhesion as though contact cement was not there or will contact cement contaminate epoxy in these areas and prevent it's cure thus yielding little or no adhesion of epoxy in these areas??

    I believe the adhesive strength of contact cement to substrate will be enough for my application if epoxy will stick to the contact cement layer with at least similar adhesive strength -- or it would be great if epoxy will "eat" through the contact cement layer and end up with epoxy adhering directly to substrate with typical epoxy adhesive strength -- but if contact cement surface will inhibit or contaminate the epoxy at these areas and result in little or no resultant adhesion the situation would be unacceptable --

    I need to know which of the 3 situations we might end up with because obviously the whole concept won't work if we end up with lack of adhesion at areas in question --
    John Stricklin

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