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Old 05-02-2005
c25 c25 is offline
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QUestion about epoxy. What is "kicking"?

Poor terminology for intructions as, even between chemists, the "let it kick before..." verbiage probably wouldn''t find agreement with regard to what "kick" meant...or at least the extent of the reaction(kick) before the next step.

Two part epoxies of this type are made up of an epoxy-functional resin & an amine-functional resin. When you mix the two the amine reacts with the epoxy to form a crosslinked network (basically two string-like polymer chains, one amine & one epoxy, react together to form what looks like a cargo net...a network). This crosslinked-network, once completely formed, is insoluble (won''t dissolve) in any solvent and it takes alot of energy(stress) to get it to fail.

There are simple tests to determine the extent of the reaction, but none of them are very good. One is a "tack" test where you take a wooden tongue depressor (popsicle stick) and repeatedly touch the mixture and pull it away. What it feels like & how it appears can give the (experienced) technician an idea of how far along the reaction is. Repeatability requires that you know what you''re doing & even then the test is shaky.

Probably the best estimate of when to take the next step would be a block of time at some temperature as the rate of the reaction will be dictated by the ambient temp. Cooler temps = slower reaction rates & longer reaction(cure) times. The rule of thumb in organic chem circles is that the reaction rate doubles with every 10 degree(C) increase in temp.

You might call the mfg of whatever you''re working with & ask for their tech service representative. Ask them how long to wait at 70 degrees F (60 degrees, 50 degrees..whatever you''re working at)..before the next step. It almost sounds like you''re refinishing a mast? This is one boating-application where the timing of the next step matters.
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