# epoxy resin catalyst (is it really a catalyst?)

**URL:** <https://boards.straightdope.com/t/epoxy-resin-catalyst-is-it-really-a-catalyst/451789>\
**Category:** Factual Questions\
**Created:** [June 4, 2008, 7:16pm UTC](https://boards.straightdope.com/t/epoxy-resin-catalyst-is-it-really-a-catalyst/451789 "2008-06-04T19:16:58Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Sigene](https://avatars.discourse-cdn.com/v4/letter/s/df788c/32.png) [@Sigene](https://boards.straightdope.com/u/Sigene)\
**Post date:** [June 4, 2008, 7:16pm UTC](https://boards.straightdope.com/t/epoxy-resin-catalyst-is-it-really-a-catalyst/451789/1 "2008-06-04T19:16:58Z")

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For epoxy resins, or other resins used in fiberglassing and the like. You have two components that you mix in specific ratios. I’ve often heard the “hardening” agent referred to as a “catalyst”. However, a catalyst doesn’t get used up in the reaction and is available continual reuse…as in the metals in a catalytic converter.

Is the hardener really a “catalyst” or is this a misuse of the term?

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**Author:** ![mwbrooks](https://avatars.discourse-cdn.com/v4/letter/m/ba9def/32.png) [@mwbrooks](https://boards.straightdope.com/u/mwbrooks)\
**Post date:** [June 4, 2008, 7:53pm UTC](https://boards.straightdope.com/t/epoxy-resin-catalyst-is-it-really-a-catalyst/451789/2 "2008-06-04T19:53:46Z")

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FWIW, I found the following at an [Epoxy floor site](http://www.epoxyandepoxyflooring.com/epoxyresins/epoxyresins.htm). (My emphasis.)

> [@](#):
>
> Epoxy **hardeners are not catalysts** and they react with the epoxy resins, greatly contributing to the ultimate properties of the cured epoxy resin system.Epoxy hardeners provide: gel time; mixed viscosity; demold time of the epoxy resin system. Physical properties of the epoxy resin system such as tensility, compression, flexural properties, etc., are also influenced by epoxy hardeners.

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**Author:** ![Sigene](https://avatars.discourse-cdn.com/v4/letter/s/df788c/32.png) [@Sigene](https://boards.straightdope.com/u/Sigene)\
**Post date:** [June 4, 2008, 8:55pm UTC](https://boards.straightdope.com/t/epoxy-resin-catalyst-is-it-really-a-catalyst/451789/3 "2008-06-04T20:55:57Z")

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Some are “catalyzed” by a free radical initiator? are these initiators really catalysts?

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**Author:** ![Solfy](https://avatars.discourse-cdn.com/v4/letter/s/848f3c/32.png) [@Solfy](https://boards.straightdope.com/u/Solfy)\
**Post date:** [June 4, 2008, 9:32pm UTC](https://boards.straightdope.com/t/epoxy-resin-catalyst-is-it-really-a-catalyst/451789/4 "2008-06-04T21:32:45Z")

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[QUOTE=Sigene]  
Some are “catalyzed” by a free radical initiator? are these initiators really catalysts?  
[/QUOTE]

The classic radical initiated polymerization results in the radical generating species chemically bonded to one end of the polymer chain. In that respect, they are, as you sugest, not catalysts. They are initiators.  
Common parlance may label them catalysts because they make the reaction go, and without them the reaction does not go, but you are right that they do not strictly meet the definition of a catalyst.

There are, however, polymerizations that are truly catalyzed (the catalyst is unchanged and available after the polymerization).