I understand the System 3 publish a booklet called "the Epoxy Book" which
contains the following remarks.
>>of particular interest has been their "the epoxy book" (see
http://www.systemthree.com/). besides a decent basic chemistry lesson,
it includes such gems as:
> epoxy resins may be applied over cured polyesters that have been dewaxed
and well sanded but polyesters
should never be used over cured epoxy resins. unreacted amine [throughout]
the epoxy inhibits the peroxide
catalyst in the polyester causing an incompl! ete cure at the interface.
sanding does NOT get rid of the
unreacted amine. the result is a poor bond even though the surface
appears cured. debonding will be the
inevitable result. (i.e., don't use polyester body fillers over epoxy.)<<
In any hand layup there will always be some unreacted resin or hardener.
This tells me I should always use an epoxy primer.
Graham
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