polyester resin for fairing

Discussion in 'Boatbuilding' started by frank92808, Dec 28, 2015.

  1. frank92808
    Joined: Aug 2011
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    frank92808 Junior Member

    hello all
    I need to some help, i am using polyester laminating resin and micro balloons for fairing compound on a small project. I am having difficulty in getting the cure right and also with it gumming up the sand paper on some batches even when adding wax. The layup with the straight laminating resin and glass cloth went well however however I assume I am not adding enough wax and catalyst for micro balloon batches. Can some one tell me what the catalyst and wax ratios should be when adding micro balloons?

    Thanks
    Frank
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    If you precisely measure the ingredients, you should get a mix that suits your application and ambient temperature with a little experimentation. One might presume that if the cured fill won't sand without clogging, it has too little wax.
     
  3. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    As you increase the viscosity of the resin with mirco spheres and other fillers it can make it harder for the wax to migrate to the surface, which can leave it tacky.

    The type of resin can influence it too.

    Catalyst level should be in the 1.5% range, but with this type of application 2% can work well.

    High humidity can inhibit the surface cure.

    The amount of wax in the solution you buy can vary, this can be for a couple of reasons, so the amount to add can vary too, but from two to four percent is common.

    The wax can solidify and separate from the styrene it's dissolved in if it sits for long time or is exposed to cold temperatures. So if the place you bought it from didn't mix it well there is no way to tell how much wax, if any, is in the mix when they pour it down into smaller containers.

    If it cooled off when you had it, and it wasn't rewarmed and mixed, then any wax floating on the surface of the mix is poured off right away and leaves little to none in the container for future use.

    Measure everything very accurately and when you find a mix that works as desired and duplicate it exaclty every time.
     
  4. SukiSolo
    Joined: Dec 2012
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    SukiSolo Senior Member

    Some of the resin fillers work better with epoxy and some are OK with polyester. I'd recommend trying a different filler, specifically known to work with polyester. I've had this type of problem before and it is nearly always a compatibility issue. If the stuff won't blend and set properly, try another filler and test that. Test a number of small different filler samples before you do any proper fairing. Polyester is cheap and quick setting so you will know in a very short time.

    It does of course mean tearing off any duff mix already on the 'build'....and replacing.

    I don't understand why you need any wax at all. It should only generally be used for surface gelcoat if working inside out ie a repair. Polyester layups cure fine without wax and can be built up quite easily whilst the resin is 'green'. Last thing you want is a barrier in the form of wax to prevent this. It does not need it (wax) to cure as a resin laminate.
     
  5. frank92808
    Joined: Aug 2011
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    frank92808 Junior Member

    thanks everyone,
    its been pretty cool the past few weeks and I did not pay attention to what the wax looked like. Now I see that it has separated so the plan is to warm it up, mix it well and give it another shot.

    SukiSolo, i used laminating resin (no wax) for the lay-up. However when i am ready to sand and fair i add wax to the lam resin. The wax (surfacing resin) rises to the surface during the cure process and seals the resin from the air allowing it to cure tack free. You are right in that you do not want this during the lamination process put it typically works great when you are ready to sand (absolutely no clogging). I make a lot of surfboards and this method works flawlessly however i never need to add any filler. The boat project i am working on needs quite a bit of fairing thus the micro spheres.

    thanks again
    frank
     
  6. SukiSolo
    Joined: Dec 2012
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    SukiSolo Senior Member

    Thanks for that info Frank. I'd try changing the brand of microspheres, some work fine with epoxy but not polyester, some work with both. Not entirely sure why, as they 'should' be neutral and inert chemically. That and very thorough mixing should sort it, good luck. Only other thing is if the microspheres have got a bit old and gained water ie high humidity. Some times pre drying a small batch helps, just before mixing into the resin, even if the use by date has not been exceeded.

    Typically the wax needs at least 10 deg C to be fully liquid, it is usually pretty easy to spot crystalisation. Also if fully mixed it gives a more 'unstickable' consistency to the resin in the pot. Personally I often locally heat the wax until clear and 'liquid' and then the resin slightly and mix these thoroughly prior to adding the 2% (typically) of hardener. If workplace temperatures are on the edge, it may take 2 or 3 hours to cure, whereas at 20 deg C it would be 20-30 minutes.....
     

  7. frank92808
    Joined: Aug 2011
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    frank92808 Junior Member

    Success! I did two things, changed the hardener ratio to the volume of resin AND filler and warmed up and mixed the wax before adding it. Sands like a charm

    Thanks again
    Frank
     
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