NJAET : Not Just Another Epoxy Thread

[dhbarr]

Beginning at
https://www.jcrocket.com/adhesives.shtml
and then adding a dash of
https://multimedia.3m.com/mws/media/646994O/3ms-tough-stuff-white-paper.pdf ,
https://www.westsystem.com.au/wp-content/uploads/2019/07/thinning_epoxy.pdf , and
https://www.epotek.com/site/files/Techtips/pdfs/tip23.pdf
we arrive at a reasonable idea of how to apply our epoxy, how not to dilute it, and appropriate temperature ranges.

Knifemakers require similar performance out of some of their products, so we also find
https://www.bladeforums.com/threads/epoxy.1353668/page-2#post-15578099 and
https://www.bladeforums.com/threads/glue-wars-2.337504/page-2#post-3236798
as well as some discussions about rifle bedding, although those guys will apparently use just literally whatever.

Closer to home, we have
https://www.rocketryforum.com/threads/list-of-epoxy-systems.62308/#post-659468 as well as
https://www.rocketryforum.com/threa...nd-technical-data-sheets.138953/#post-1668062

Taking it all together, it seems relatively safe to select Henkel / Loctite / Hysol EA E-120HP as our fin root adhesive. Hooray!

So we zoom in on the e120hp and find the TDS as well as SDS for Part A and Part B:
https://www1.mscdirect.com/MSDS/MSDS00012/00611897-20151209.PDF
which confirm that our ingredients are:

• Part A -- Off-white to beige Epoxy Resin
  • Phenol polymer with formaldehyde, glycidyl ether -- 40-50 wt.%
  • Epichlorohydrin-4,4'-isopropylidene diphenol resin -- 30-40 wt.%
  • Amorphous fumed silica -- 1-5 wt.%
• Part B -- Amber Polyamide Hardener
  • Amine adduct ( Proprietary ) -- 60-100 wt.%
  • Tetraethylene pentamine -- 10-30 wt.%
  • Triethylenetetramine -- 5-10 wt.

Question(s) for the group:

• Are we aware of any reasonably similar compositions that are
  • substantially cheaper and/or
  • readily available in bulk qty's?
• Have any of us actually documented a 65C/150F cure schedule?
• If so, how did you know you wouldn't negatively affect the tube?
• Any consideration given to matching up the chemistries between laminating and affixing epoxies?
• Has anyone done masked bead or soda blasting on fin root attachment areas ?

 

[David Schwantz]

You can buy Hysol in case lots. 10 packs. Also Dreamworks RC has 5 packs.

 

[rharshberger]

Ease of use and meeting the requirements of our builds determines the epoxy of choice for me. I generally do not build "high performance" rockets so why spend large amounts of cash for a "superior" epoxy when the $65 a gallon stuff has all the specifications needed for the build, requires no cure cycle beyond room temperature so no extra equipment needed etc. The prevalence of US Composites, West, Aeropoxy, System Three, Pro Line, Rocketpoxy and a similar epoxies is due in part to ease of use, cost, and availability. If I were building a minimum diameter mach 2+ screamer then the Hysol's and Cotronics epoxies start to come into play for serious consideration, at that point I would also start looking a pre-preg carbon as well for the build.

 

[dhbarr]

Nobody's done elevated temp cure on e120hp?

Nobody's beadblasted FG or CF?

Nobody's matched up the chemistry between their adhesive and laminating epoxies?

 

[tfish]

I've not done any of those tests.

But I do, watch ebay for ..expired epoxy. I've gotten really lucky three times. recently I bought eight - HP120 1.69 tubes and a coupe of cans of loctite spray activator surface prep stuff for $55.
Yep it's expired but works for what I'm doing.

Tony

 

[watheyak]

You bring up some good questions. A project am currently working on is using Cortonics 4461 and 4525 almost exclusively.

Except the tube... Which I did not make.

The plan is to post cure them as specified temps up to 450°. It hadn't occured to me that I might fry the tube in the process. I'll look into that. My gut feeling is that once the tube is fully cured, unless there's stress being applied, temps above Tg won't hurt it. But I don't know this for sure.

 

[dhbarr]

You bring up some good questions. A project am currently working on is using Cortonics 4461 and 4525 almost exclusively.

Except the tube... Which I did not make.

The plan is to post cure them as specified temps up to 450°. It hadn't occured to me that I might fry the tube in the process. I'll look into that. My gut feeling is that once the tube is fully cured, unless there's stress being applied, temps above Tg won't hurt it. But I don't know this for sure.

Cotronics 4461 is actually one of the types I was reading up on when doing this thread, along with PTM&W PT2846. I'll have to check out the 4525.