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-   -   QUestion about epoxy. What is "kicking"? (http://www.sailnet.com/forums/gear-maintenance/11606-question-about-epoxy-what-%22kicking%22.html)

duffer1960 05-02-2005 05:41 AM

QUestion about epoxy. What is "kicking"?
 
The instructions for using two part epoxy say to wait for it to "Kick" before doing the next step (whatever that may be, depending on what you are doing). What does that mean? Is that when the epoxy actually sets (not cures, but when it becomes unworkable)?
Thanks.

c25 05-02-2005 09:23 AM

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.

duffer1960 05-02-2005 11:11 AM

QUestion about epoxy. What is "kicking"?
 
No, I''m not refinishing a mast, just doing some minor patch work. The instrustions say to wait until after the epoxy "kicks" before adding another coat/layer.

jbanta 05-02-2005 12:28 PM

QUestion about epoxy. What is "kicking"?
 
"kicking" the time when the chemical reaction completes and the resign hardens. Don''t touch it will be HOT..You will actually see the reation there will be no guess work to tell when the hardner has "kicked". I have done some major patch work closing over a hole in my bottom where a sail drive tail once projected. You won''t have any troblem knowing when you can add more glass and resign.


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