On Tue, 8 Dec 2009 13:51:47 -0800 (PST), mx wrote:

On Dec 8, 12:28*pm, "Lew Hodgett" wrote:
wrote:
Will all epoxies bond to one another?

There are two (2) types of bonding, chemical and mechanical.

Chemical bonding occurs when a follow up layer of resin is applied
over an epoxy surface that has not totally cured.

Mechanical bonding occurs when a layer of epoxy is applied over a
totally cured epoxy surface.

You appear to be describing old work, thus mechanical bonding will
apply.

The premade glass parts are old (one is "new" but was made at least 6
months ago). Their surfaces to be bonded are fairly rough, so should
give a half-way decent mechanical bond. The glass tape is to insure
that the load is carried out over a large area of the old hull, since
its layup is not terribly thick.

But since I'm considering using 2 different epoxies for the fillet and
new cloth reinforcement, i was uncertain if they might be incompatible
in forming chemical bonds between the two new layers, or if it could
be assumed that any two common epoxies would stick to each other
chemically if the first layer is only partially cured.

Thanks,
Mike

Essentially "epoxy" is the same stuff, no matter where it comes from.
Certainly various sellers modify their product for some specific
purpose but basically they are all epoxy. So they will stick to each
other. Sand the old layer with a coarse sanding disk, wipe with
acetone and have at it.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)