Resin cure time under vaccum

Discussion in 'Fiberglass and Composite Boat Building' started by sadiq, Oct 2, 2014.

  1. Steve W
    Joined: Jul 2004
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    Steve W Senior Member

    Ok, you used cobalt so it appears you are using PE resin so it should have cured in just a few hours. How much catalyst did you use?

  2. rxcomposite
    Joined: Jan 2005
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    rxcomposite Senior Member

    Was it not discussed somewhere in this forum that Poly resin when subjected at very high vacuum, the liquid boils off and some of the volatiles are sucked out, preventing cure?

    I remember that poly cures by consuming the MEKP during the reaction process unlike epoxy which needs one epoxy molecule for each harfener molecule.
  3. Steve W
    Joined: Jul 2004
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    Location: Duluth, Minnesota

    Steve W Senior Member

    I have no cure issues infusing with VE, most of Derek Kelsalls cats are infused with PE with no issues. If it didn't cure somebody didn't catalyze or mix it right.
  4. sadiq
    Joined: Oct 2014
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    Location: Pakistan

    sadiq Junior Member

    gonzo, our project is related to mechanical engineering. not chemistry. We just want to cure somehow.

    tell me some ways to reduce the viscosity of resin, the shopkeeper said, to mix the styrene. What do you say? will it work ? and what about the cure time when styrene will be added.
  5. AndySGray
    Joined: Jun 2014
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    Location: Cayman

    AndySGray Senior Member

    There's an easy way and a hard way.

    The easy way is to get the recipe - your unhelpful shopkeeper should already have lost your business, find someone else or telephone the manufacturer helpdesk.

    So the hard way - get lots of pots and a stopwatch.

    Change only 1 thing at a time and measure how long it takes to start hardening.

    You say 1 drop of cobalt was too much - try half a drop?

    How to get half a drop ? - put 1 drop in 10ml of styrene and add 5ml, TIME IT
    repeat with 2.5ml, time, repeat with 7.5ml, time, repeat with 1ml, and time it.
    Ah but now you're messing with the styrene quantity too - so make up to 10ml each time with neat (no cobalt) styrene before you add the MEK and start the clock...:confused:

    Going to take time and waste much reagent.

    EVENTUALLY you'll find a working ratio - now can you see why Gonzo keeps telling you to get the spec sheet?

  6. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Adding styrene sort of works, but a laminating resin already has products added to increase the viscosity for hand application, so the styrene is doing battle with a thixitrope to lower the visc. An fusion resin has no thixirtope added and will work much better. A small amount of styrene won't change the gel time a great deal.

    Most polyesters don't need cobalt added at the time of use, it's been added by the manufacturer when first made, but in some parts of the world it may be added later so the resin has a longer shelf life, or the resin can be adjusted as needed for each project. This reduces the types of resin that need to be stocked.

    The description of the resin on their website says it's highly reactive (fast cure), this doesn't mean much without referencing some kind of actual gel time (15 minutes, 20 minutes etc.). For infusion you typically want a less reactive product so the part has time to fill completely. When making your first part you won't know the exact fill time so you target longer gel time than you think you may need.

    The cure time will be the same under vacuum, the laminate thickness and ambient temperature will have a huge affect on gel time though.

    You didn't say how much resin you were mixing up at one time, but if you are adding cobalt the amount added needs to be very accurate, it could be in the .10% range, so just adding drops isn't going to get you there. Mixing one gallon at a time can be tough, mixing 5 gallons can be easier (I know, go with liters), the greater the volume mixed at one time the better the accuracy.

    Some resins may need cobalt plus an inhibitor added to stretch the gel time out to where you want it.

    The following link will explain many thing in detail, just go to the chapter you want and click on it.
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