MAS epoxy and chlorinated water?

I have two foam seats for my Chesapeakes that are constructed with MAS epoxy.  That epoxy doesn't seem to tolerate exposure to chlorinated water very well.  After a couple hours' exposure to chlorinated water, it turns into a white, crusty mess and loses much of its strength.  See picture.

Strangely, and very fortunately, nothing similar seems to happen to the boats themselves.

Can anyone explain why the foam seats are affected this way?  Or better yet, suggest an alternative adhesive that will tolerate chlorine exposure like this?


Someone will probably wonder where I'm paddling.  Local clubs organize rescue classes and practice days in indoor swimming pools.  Specifically high school pools, which tend to be highly chlorinated.

picture of chlorine-exposed epoxy

5 replies:

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RE: MAS epoxy and chlorinated water?

Hi David, 

can you confirm that the glue is really mas epoxy? (did you build the seat yourself?) 

most work with closed cell foam is with rubber cement or a silicone would be pretty unusual to use mas epoxy.  that said, properly cured mas epoxy should have no trouble with clorinated water....which is why the rest of the boat is fine.  

my suspicion is that you have some other glue involved here (like a 5 minute epoxy).  i have done rolling practice in my CLC kayaks in clorinated pools and have had no trouble like shown in your my guess would be that a glue was not water compatible...and that the issue is not even about clorine.


RE: MAS epoxy and chlorinated water?

   Can confirm that the epoxy is MAS.  Assembled the seats myself ( not recently ).  Standard MAS resin with slow hardener, purchased from CLC.  Potentially not the best choice for this application, but I had plenty of it, and never had any other issues using it for miscellaneous projects.

   There is a better choice, I just don't know what it is.  I purchased some 2-layer foam from McMaster-Carr, that has a soft side and a hard side.  I used that for a backrest, since the hard part provides support while the soft layer cushions.  Obviously the two types of foam are adhered to each other with something.  Whatever that adhesive is, seems to be completely fine with chlorine.  If I knew what it was, I'd buy it... but I have no idea.



RE: MAS epoxy and chlorinated water?

Thanks for the clarification David.

fwiw, my experience is limited to the closed cell foam (which i believe is actually a form of rubber) that is sold by CLC (and other kayak bits resellers) for the making of seats.

so, as mentioned above, i have used rubber cement as my typical 'go-to' glue for seats and, in general, it has held up well even after pool rolling sessions.  i have also used silicone glue.

my understanding on the rubber cement, and my experience, is it actually melts the underlying material and joins it its basically like a continuous piece if applied properly.   so the thing here is the chemistry is important and the word 'foam' is used loosely but can refer to a lot of different products of very different characteristics....some of which are expressly incompatible with epoxy.

that said, while you may have  had the epoxy work for some period of time, i imagine it would break down relatively quick if used for a seat.  cured epoxy is quite brittle when subjected to the kind of flexing you would expect a seat to endure (e.g., take a little piece of thin cured epoxy and flex it over and over again.....and it will break easily).  its strength is as a glue within a relatively rigid component.


RE: MAS epoxy and chlorinated water?

In a properly maintained pool, the water only contains 2-4 part per million chlorine.  At that concentration, it will not have any effect on properly cured epoxy over the short term.  There are many other chemical in pool water (stabilizer, anti-scale, stain fighters, etc) that could be the culprit, but they also are normally at low concentration and should not have any impact.  If there was something in the water that attacked the epoxy, the exterior was protected by the varnish.  Do you have any damage in areas not covered by varnish, like in the cockpit on the underside of the deck?

If there is not damage on the un-varnished areas, the problem is likely incomplete cure of the epoxy used for the seat.  It could have been an error on your part, but more likely chemical contamination with something on the foam.  Porous subtances like foam will pick up and retain virtually every thing they come into contact with.  During manufacture, cutting, packing and shipping, that foam had a lot of chances to pick up something that epoxy does not like.

I agree that epoxy is really not the best for foam.  I prefer contact cement.


RE: MAS epoxy and chlorinated water?

   No other damage anywhere on the boats.



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