mix n' match hardener?

Are all epoxy resins the same, and the difference only in the hardener?    I ask because I found at the NAPA Auto Parts store some cheap epoxy, like a can of Bondo Fiberglass Resin, pretty cheap at $17 a quart.   The same quantity of MAS epoxy is considerably more.   Dunno why MAS is so much pricier than two years ago, but it is.   Now these NAPA resins come with a tiny tube of hardener which hardens in 10 minutes, much too fast, and doubtless they all blush like the dickens (I nearly said like Doris Day in a porn film but the image is too off-putting).  I wonder if I could use a MAS hardener with NAPA epoxy, and cut costs.  Anybody tried mix n' matching like that?  This is for sealing the wood of a Newfoundland paddle before varnishing.  Even the cheapest CLC "economy kit" of MAS products way exceeds the cost of the paddle.          

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RE: mix n' match hardener?

I wouldn't do it.  Although the basic organic chemistry is the same (an epoxide group bonding to an amine group), each type of resin is specially formulated to chemically work with its own hardener, and vice versa.  There are also copolymers added to epoxies that make the individual formulations unique, and therefore yield slightly different properties.  Also, bondo, if I remember right, is a vinylester-based resin, which is chemically quite different from epoxide-based resins.  Don't quote me on that though, its been a while since I studied organic chem in college!  

And besides, you could always just make more paddles and put that epoxy to use!


RE: mix n' match hardener?

Absolutely not.

Bondo is polyester resin. That little tube is catalyst, not hardener. MAS is an epoxy resin. Polyester resins absolutely do not work with epoxy hardeners. You will end up with a gummy toxic stinking mess.

Polyester resins do not bond well to wood. And to make things worse, polyester lets water pass through.

As far as economies go, you could just skip the epoxy and depend on the varnish to protect the wood from the water.




RE: mix n' match hardener?

Thanks Chris & Laszlo, for saving me from myself.  As to using only varnish to portect the wood--I find that a little (a very little)  333 does rejuvenate last year's varnish, so I have taken Laszlo's advice and varnished the thing and it looks like it will work.

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