Messages Archive 2010

Subject:
Re: question of how
Response To:
question of how ()

Jim Dillon
Bill and others,
Interestingly, the 2010 Presidential Medal of Technology and Innovation was just given to the inventor of cyanoacrylate glue, Harry Coover, who was at Eastman Chemical at the time.

Anyway, CA is a generic name for a class of monomers that polymerize on contact with electron-rich chemical groups like amines, water, hydroxys etc. Depending on the type of CA, the polymerization can be very, very rapid, or much, much slower. Unfortunately, the faster the rate of polymerization, the more exothermic the reaction, and the faster the breakdown of the polymer. This rapid breakdown of some types of CA leads to an inflammatory response if used for tissue repair. This response is caused by the degradation byproducts of formaldehyde and a cyanoacrylate homologue based on the starting material. It is this response that led, wisely or unwisely, to the holdup on FDA approval for the tissue repair products.

However, CA can be synthesized in many flavors. Generally speaking, the longer the hydrocarbon chain (i.e. ethyl, butyl, octyl etc.), the slower the rate of degradation and the more likely the polymer will be stable over the "long" term.

The accelerators are simply dilute solutions of an electron-rich ingredient such as an amine that promotes rapid polymerization.

Regarding the use of CA in wood repair, I haven't really kept up on recent changes (if any) in CA formulations, but the chemical principles should remain the same and I would guess that water/moisture would be the Achilles heel of CA use in wood repair, but we could be talking years and years here depending on the type of cyanoacrylate used. I have no information on creep of CA glue, at least I don't recall anything, but all my textbooks are in storage. I would again guess that the longer alkyl CA would display better creep properties and may give better life expectancy.

I will be away from my computer for most of the day but will check back later to try to answer any questions.

Jim

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