epoxies and saponification
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griffinhall



Joined: 01 May 2006
Posts: 6
Location: virginia

PostPosted: Thu May 04, 2006 5:29 am    Post subject: epoxies and saponification Reply with quote

Some epoxies have alkalinity issues as they cure, which can lead to saponification thereby causing primers or paints that are alkyd- based to not fully adhere.

I have used pc woody, abtron and rot doctor products and have called all to ask if their products are in this catagory. All claim that they do not ,but all I spoke to seemed to have a tenuous grasp on the reaction, making me uneasy about their replies.

Does anyone know which products have this issue?

Thanks

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johnleeke
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Joined: 20 Aug 2004
Posts: 2972
Location: Portland, Maine, USA

PostPosted: Thu May 04, 2006 1:31 pm    Post subject: Reply with quote

June:

The amine component of the epoxy chemistry does not fully react with other components leaving a tacky or waxy feeling deposit at the surface of the cured epoxy. This somewhat alkyline deposit is said to combine with oil in primer in a process called saponification, forming soap-like compounds that can result in adhesion problems for subsequent coatings. In my experience this happens with Abatron's LiquidWood. One method of dealing with it, as recommended by Abatron's technical support, is to let the A & B parts stand after mixing for a 10-15 minute "induction period" to get the molecular reaction going. Another is to sand the surface after curing and before any further treatments. It is our standard practice to sand or trim away all cured epoxy treatment surfaces before further treatment.

Mentioning only Abarton's LiquidWood here should not be taken to mean that other products do not have the saponification issue.

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Last edited by johnleeke on Sun Aug 20, 2006 9:04 pm; edited 2 times in total
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Jhstahl



Joined: 20 Aug 2006
Posts: 5
Location: Upstate New York

PostPosted: Sun Aug 20, 2006 8:46 pm    Post subject: Reply with quote

My name is John Stahl. System developer for Advanced Repair Technology. We provide a flexible epoxy product called Prima-trate and Flex-tec.

http://www.advancedrepair.com/architectural_epoxy/architectural_epoxy.htm
Some epoxy compounds produce more amine blush than others. Perhaps this is what you refer to as saponification.

Proper mixing ratio is a potential problem. If the materials are not mixed in the correct ratio, problems with excessive amine blush can occur.

Consider trying an epoxy material with little amine blush and no induction period. Our system addresses these issues.

Other things to consider are: Ease of use, flexiblity, sandablity, waste, VOC's.

Cheers,

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John H. Stahl
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