hot weather catalyst

Discussion in 'Fiberglass and Composite Boat Building' started by brokensheer, Jun 10, 2014.

  1. brokensheer
    Joined: Jun 2009
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    brokensheer Senior Member

    I work with polyester resin and am looking for a good hot weather hardener, love to hear what you think !
     
  2. ondarvr
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    ondarvr Senior Member

    It depends on several variables.

    Thick or thin laminates, methods used (hand lay, chopper gun, infusion, etc.), size of part and gel time required.

    Plus by picking the correct resin you may not need to change the catalyst.
     
  3. brokensheer
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    brokensheer Senior Member

    One answer I got on the "net" was to mix 1/2% at the lowest I never heard you could go that low? I have seen jugs labeled " hot point 90" Cadox M 50

    CadoxM 30 hence my question
     
  4. slneatboat
    Joined: Nov 2003
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    slneatboat Junior Member

    I have always understood that the M50 is the standard catalyst and M30 is a slower one, ie you can then still mix at 1% but get an extended gel time if that makes sense, used it once many years ago and believe it was coloured to avoid any mix ups.
     
  5. ondarvr
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    ondarvr Senior Member

    It all goes back to my originals questions to you.

    The lowest % is very dependent on many things, the resin and how it will used is one of the most important, but .5% is too low for just about any resin, it may get hard but the physical properties will be poor. At this level you could easily be making trash parts.

    .9% is about as low as any resin we supply should be used, many you wouldn't want to go that low on. And again, it depends on how it will be used.

    The catalyst suppliers would do everyone a favor by eliminating the "30" type catalysts, they are about worthless. It is nothing more than full strength catalyst with more diluent, this is not what you want to use. You can't reduce the amount of the active ingredients in the catalyst below a certain point and still get a good cure, the same % of active ingredients are needed whether you use 30 or 50 (some call theirs 30 and 9, DDM9, MEKP9, etc). So to get an equal cure more of the 30 needs to be used, the problem is the diluent, it’s a worthless and potentially harmful contaminate when more is added to the resin or gel coat. The misconception is that you can add the same amount as the higher strength product and get a longer gel time and still achieve a good cure.

    There was a time when it was sort of needed, it had to do with how accurately the equipment could dispense catalyst. At lower levels the pumps had a difficult time metering out a reliable %, so with a diluted catalyst they could set the pump at a higher %, but still reduce the amount of active ingredients being delivered. This way they could more reliably get good and even catalyzation.

    There are many different types of catalysts that can be used, and then there are blends of these types that can fine tune the cure and peak exotherm to the exact needs for a specific part or laminate.
     
  6. brokensheer
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    brokensheer Senior Member

    great info. so for example if I gel coated a small part under 2 SF at 2% then skinned it with 1.5 oz CSM at .5% then the structual Laminated are at 1% am I good?
     
  7. ondarvr
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    ondarvr Senior Member

    The skin at .5% would most likely be trash, the cure would be poor, which compromises the physical properties, which includes water resistance. Skin coats need more catalyst due the reduced mass, there just isn't enough energy generated to complete the crosslinking at low catalyst levels. A low catalyst level in the skin almost guarantees there will be a good deal of post cure taking place, resulting in a poor surface profile. Skins should be at 1.5% minimum, more often at 2% for best results. 1% might be OK for the structural portion, but again, it depends on the exact resin, laminate thickness, ambient temperature, etc.

    If the problem is high temperatures, you can buy resins with longer gel times, frequently resins sold in box stores have very short gel times, I have no idea why they do this, it only makes working with it more difficult for a newbie. When you buy resins at shops specializing in these products you can get longer GT products, with GT ranges from 15 to 27 minutes being common, but longer is possible.

    By adjusting the type of catalyst (not talking about 30) you can shorten or lengthen the GT significantly and still get a very good cure while still staying in the safe zone on catalyst level.

    All this GT testing is done at 77F, go up from that by 15 degrees or so and you will cut the GT in half, going that same amount lower than 77 will about double it.

    These different GT's are made so the fabricator can keep the catalyst level in the 1.25 to 2.25% range, this is considered the safe zone.
     
  8. ondarvr
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    ondarvr Senior Member

    And at 2 SF you shouldn't have a problem with higher catalyst levels unless there is a great deal of detail in the part and the temps are high.
     
  9. redreuben
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    redreuben redreuben

    Been awhile since I had a roller in my hand but I never went below 0.75%
    And for your skin layer you must stay high or the gelcoat will wrinkle from styrene attack if not driven off by a good cure.

    If you want to do it properly inhibit the resin and leave catalyst levels where they need to be.
     
  10. SamSam
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    SamSam Senior Member

    Or if the styrene fumes, which sink and puddle, are not allowed to drain off or sucked/blown away by ventilation.
     

  11. brokensheer
    Joined: Jun 2009
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    brokensheer Senior Member

    The condition I am battling is the outside temps, mixing a qt. at a time I loose a good bit of material and I am just searching for a better way! all the info here is enlightening! Thanks
     
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