Vinyl Ester Catalyst question:

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#1

Can any of you guys tell me which catalyst will provides longest possible gel time (VE resin) on a single layer laminate of 9oz 7781 eGlass. The process I plan on using is: Wet layup then vac bag. Laminate size = 12 feet x 6 inches. I need the gel time to be long enough time to wet out the cloth, remove air bubbles, add a stack of: peel ply, perf release film, bleeder/breather, bag and pull a medium vac. The laminate must be under vac long enough to pull the excess resin from the laminate before the resin starts to gel… How long it takes to pull excess resin from the laminate and compact it nicely I don’t know… I’m guessing at least 10 min or so?

I’m curious about MCP and MEKP-925H (ss below)

Oh, BTW I’m in AZ (USA) with ambient temps of 70-75 degrees (AM) and 90+ degrees during the daytime. I need a USA supplier for whatever catalyst you guys recommend…

Thanks for your help!
James
Phoenix, AZ

HERMAN mentioned the following in a post last April:
MEKP-9: a slow version is MEKP-9H, even slower is MEKP-925H, some 3 times as slow as MEKP-9. The peroxide for keeping viscosity low is HDP-75. Excellent wetting of the fiber, approx same results as MCP peroxide

#2

If you have resin which is not preaccelerated, than slight decrese in amount of cobalt will give you longer gel times. Just test it priror to work and test with the technick you will use. I get dion VE to gel after 90min.

#3

MEKP 925H is the slowest, but the difference with MCP is not much. MCP has a lot lower peak exotherm, good for thicker laminate.

See if you can dig up some comparison chart from Syrgis.

Edit: did the digging for you (in my files…)

#4

Thank you for the comparison chart! Very useful information… It looks like the Norox MCP, Norox MEPK 925H, Norox HDP-75, Andonox CH and Andonox TLC-88 all have 37+ min gel times (awesome!). A few quick follow on questions:

  1. Is there a USA supplier that sells the above mentioned initiators?
  2. Can these initiators be used with any VE resin thats been promoted for use with MEPK9 or will I need to pick up a new batch of VE resin and promote specifically for these initiators?
  3. Do any of the above initiators change the final max thermal distortion temps of the cured resin? My current VE resin with MEPK9 has a TD near 220 degrees F.
  4. Should I be concerned with the lower peak exother (as in will I have any problems with a thin 1 layer laminate fully curing with ambient temps between 75-90 degrees?

Thanks again for sharing your knowledge with a noob!!

#5

  1. No idea. I know Syrgis sells in the USA as well, so search around a bit. Startingplace would be www.syrgispi.com, see which distributors they have. Working your way down from the top usually is faster than blindly searching for the bottom end.

  2. Yes, should be do-able. Make a test though.

  3. No, these should not be harmed. Keep in mind a final cure can only be reached after postcure.

  4. If you are aiming on MCP: Even though the peak exotherm is low, the final cure, even in thin laminates, is really good. Just give it a bit of time. (or heat). But your concern in general is right. If you are doing thin stuff, take a look at CHM-50 or 30.

#6

Try Express Composites.com