Vinyl Ester Resin Post-Cure Mandatory?

Discussion in 'Materials' started by Johnfirstime, Nov 20, 2018.

  1. Johnfirstime
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    Johnfirstime Junior Member

    I am planning to infuse some rather large parts and was considering the use of a vinyl ester resin. I was wondering if it would be possible to only cure vinyl ester at ambient temperature without it ever seeing a high temperature post-cure? Are vinyl ester resins stable enough to be cured at only room temperature and will they gain sufficient strength? I recognize additional strength can be gained with a high temp post cure but I am not too concerned with having the highest strength possible and would prefer not having to heat cure these parts.

    Thanks in advance for your input!
     
  2. ondarvr
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    ondarvr Senior Member

    Its not that common to post cure items made with VE resin, not that it can't be done, because it will increase the physical properties, it's just that for most applications it's not needed.
     
  3. Johnfirstime
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    Johnfirstime Junior Member

    Thank you for the reply. This was the feeling I had but it is reassuring to hear this advice from those more experienced than me.

    I've seen some VE data sheets and they usually mention a post-cure when listing the mechanical properties of the resin. Would you estimate that a non-post cured VE resin will achieve only about 70-80% of the strength and stiffnesses advertised?

    Thanks again!
     
  4. rxcomposite
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    rxcomposite Senior Member

    In general VE resin mechanical properties is a little bit lower than regular cured epoxy. Epoxy can attain good strength at ambient air curing. Post curing VE will raise its mechanical properties equivalent to a ambient air cured epoxy. But then, epoxy can be post cured, raising the bar higher again than post cured VE resin.
     
  5. ondarvr
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    ondarvr Senior Member


    Yes, most Data sheets do list the post cured physical properties of a resin, it's really the only way to compare them apples to apples.
     
  6. redreuben
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    redreuben redreuben

    Heat curing parts is not without its issues it can blow up any voids or trapped solvents delaminating or blistering your product.
    A boat yard I worked in was giving the pvc foam for the cores a heat treatment prior to laminating to drive off solvents/gases and avoid this.
    Just make sure your catalyst level is always within spec and you will be good, if you want a post cure without to much trouble put the finished pieces after they have cured for a week or so under some black plastic in the sun for a few hours to get about 50C.
     
  7. fallguy
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    fallguy Senior Member

    Care to express thoughts and reservations about an epoxy post cure full hull?

    Two hours at 145F

    I will run some tests for sure.

    I already had a problem with one hull sitting under black cover in sun. We had not done any venting of watertights and it looks like stretch marks on each side of the hull for a foot or so. We don't get too hot here generally; sometimes 90s.

    If I have an air pocket, what to expect? I am sure I have some.
     

  8. redreuben
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    redreuben redreuben

    Generally speaking air bubbles only pop when just under gelcoat although if it is under the waterline they will come out over time in polyester layups through the dreaded osmosis.
    If its an infusion I wouldn't worry, hand laid mmm not so sure, for 2 hrs it ought to be good. Is 145f as recommended by the manufacturer ?
    I don't have a lot of experience with post cures and all have been vinyl ester laminates. The preference as I understand it is as low a temp as is needed over a longer time than short and hot.
    My suspect memory on the vinyl ester full boat cure we did on a Farr 9.2 was 45-50c overnight. That boat won its Nationals because of superior rig tension upwind.
    Also give the boat a few weeks at ambient temp before curing as a hot cure when green can give horrible print through of fabric, foam lines and what have you.
    I've seen bulkhead lines print through 12mm foam on a green hull wheeled out into the Perth sun. (poly lay up)
     
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