Type A epoxy resins contain a small amount of wax. The curing epoxy is hydroscopic: The resin draws moisture from the air; this will interfere with the polymerization process and drastically slows down the curing process to the point of staying tacky for months. The wax film prevents the hydroscopic action. Type B epoxy resins (so called laminating resins) do not contain the wax. Their intended use is for multiply lay-ups in quick succession before the first or under laying lay-ups have cured. The final lay-up would use Type A resin for open air room cure. Vacuum bagging would use Type B throughout. Unless the label says otherwise, you can assume the resin is the Type A containing the wax. The resins used in polyester and vinyl ester tend to dissolve the surface of cured epoxy, which then resets in the curing process to effect a tighter bond. Do not confuse this ester to epoxy bond as a true polymer bond. These are totally different families of chemicals. It would be like saying lizards and birds lay eggs, so they should be pretty much the same animal. As stated in the previous post, it's not a good idea to mix systems. Sid Wood, Tri-gear KR-2 N6242 Mechanicsville, MD, USA sidney.w...@titan.com
-----Original Message----- From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net] On Behalf Of cartera Sent: Monday, August 09, 2004 12:13 PM To: KRnet Subject: Re: KR> Epoxy Varnish on Spars Good Morning This is a misconception, cured epoxy does not leave a waxy residue only in the esters does this happen. That is why one if necessary can put polyester on epoxy but not epoxy on any polyester. Furthermore, it's not a good idea to mix systems. Suggest that a thorough research be done on resins before this misconception is thrown out. This is why it is not a good idea to use varnish on the inside for sealing, but epoxy diluted with alcohol then one does not have to sand out varnish in the event that further gluing has to take place. However, it should still be roughed up before gluing for adhesion. Happy Flying! patrusso wrote: > Cured epoxy leaves a waxy residue that must be cleared off from surfaces > that will be reglued to attach other parts. You may find it easier to finish > you rib and other attachments to the spar before epoxying. > ----- Original Message ----- > From: <rick...@comcast.net> > To: <kr...@mylist.net> > Sent: Monday, August 09, 2004 1:48 AM > Subject: KR> Epoxy Varnish on Spars > > > >>I have some epoxy varnish left over from painting the inside of the fuse. > > Is it OK to use it on the spars? They're closed, but I haven't begun to > assemble the wings yet. > >>Rick Coykendall >>KR-2 >>rick...@yahoo.com -- Adrian VE6AFY Mailto:cart...@spots.ab.ca http://www.spots.ab.ca/~cartera
