Epoxy versus vinyl ester

Discussion in 'Materials' started by Roly, Sep 25, 2010.

  1. Roly
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    Roly Senior Member

    1 person likes this.
  2. waikikin
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    waikikin Senior Member

    this apparently the results observed............ "Since the saturation levels
    of moisture uptake dictates the property of degradations
    in the materials employed for underwater
    applications, vinylester based composites proved
    superior to epoxy based specimens."

    thanks for posting Roly, regards from Jeff.
     
  3. Roly
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    Roly Senior Member

    Lol...PAR. Wondered how long it would take! You are totally forgiven, for thinking it...
    Yes,that was the first thing I noticed as well. It was published in an Iranian journal though.
    The research was done in an Indian Engineering facility.

    Perhaps someone has an insight into the nationality of the dominant epoxy players as opposed Vinyl ester?
    Vested interests could play a part in it getting published in a western journal.

    Or, if the researchers have a financial interest in vinyl ester production. It could be spurious.

    ad nauseam

    Pity this is how the world works.
     
  4. rwatson
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    rwatson Senior Member

    The interesting thing is how much all combinations degrade after X days - I would hope (and it seems to be after a quick read) that these tests were done on samples without Gelcoat or paint protection - or a lot of boats are in big trouble.
     
  5. TeddyDiver
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    TeddyDiver Gollywobbler

    Just an observation.. but nobody leaves carbon/epoxy without after curing so in that regard the test doesn't prove nothing. Note also the wt% were btw 0.5 to 0.9 in all samples and there weren't any noticeable increase in the moisture levels after first week. Interesting however..
     
  6. rwatson
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    rwatson Senior Member

    I was dismayed at the tables on page 97

    eg Percentage Ultimate tensile strength in 170 days - between 25% and 30%

    How close is that to real life ?
     
  7. TeddyDiver
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    TeddyDiver Gollywobbler

    We got to have more serious issues with greenhouse gases before it's real..
     
  8. waikikin
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    waikikin Senior Member

    Every one finds themselves in hot water now & then:)
     
  9. PAR
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    PAR Yacht Designer/Builder

    Well, Roly I changed my mind, as I've been pissing people off in the last few days it seems, but I'm glad you saw it.

    I sent a copy of the PDF off to a buddy of mine at West System. I quickly glanced over the contents and quickly noticed assumsions and omissions, which aligned with, well "consideration" shall we say, though this is purely speculation at this point.

    Considering the source and the absolutely unreliable nature there of, it's difficult to accept any of it. It's a bit like having some one try to convince me, the BS-1088 stamped plywood they just bought from a Chinese company, at 1/3 the price of any one else's BS-1088 is actually going to meet the Lloyds standard that's stamped on it. The track record just suggests this isn't going to turn out well.

    Tom will get back to me by mid week and I'll report back as to what he thinks. After 28 years or so at West System as a technical adviser, he'll have a clue about it, but what I saw was BS.
     
  10. apex1

    apex1 Guest

    Well, you said it right. We can produce almost every result we want when we "tune" the test right.

    This test proves nothing, absolutely nothing.

    But I would claim that several thousand boats built in either material, and tested in the environment they are designed for, proves this test wrong.

    So easy is colour TV, right?
     
  11. jonr
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    jonr Senior Member

    So take your favorite epoxy and vinylester and duplicate the test for 30 days. Speculation about bias in the test is mostly wasted effort.
     
  12. rxcomposite
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    rxcomposite Senior Member

    Marine Composites by Eric Greene and Associates have long stated that "Some advantages of the vynil esters, which may justify their higher cost, include superior corrosion resistant, hydrolytic stability, and excellent physical properties such as impact and and fatigue resistance. It has been shown that a 20 to 60 mil inner layer with a vynil ester resin matrix can provide an excellent permeation barrier to resist blistering in matrix laminate."

    Professional Boatbuilder magazine also ran an article about "blistering" some many years back. The article reccomends a vynilester resin matrix on the initial (after gelcoat) laminate.

    Vynil ester drawback is its low Barcoll hardness reading and high elongation, hence it did not became popular to use "vynil ester only" on the whole boat.
     
    Last edited: Sep 27, 2010
  13. rwatson
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    rwatson Senior Member

    So what would they put on the Vynilester laminate ? - Epoxy or Poly ?

    If Poly - isnt that going to be a compatability issue, if Epoxy, thats a better choice than Vynil and really makes the Vynil redundant ?
     
  14. Landlubber
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    Landlubber Senior Member

    rwatson, the vinyl ester is the resin mate, not the reinforcing fabric.

    ...note also that these tests were done from 50 deg C up, just how many boats live in water temps that high...we would all look like Hianan Chicken if we fell in......
     

  15. MikeJohns
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    MikeJohns Senior Member

    Higher temperatures accelerate the process but they don't create the problem it's valid to conduct these sorts of studies at higher temps. They are just speeding up the saturation. The rate is relative to the temperature. You can validate the studies with standard temperature sample 3 months down the track and they correspond.


    For example, plywood. The most reliable immediate test is to even boil and torture it a few times, if the glue fails then the long term wet durability is going to be poor. Same process really.

    Micro mechanics of composites is interesting, they rely on a matrix fibre bond, but that bond fails quite easily from several mechanisms.
    It's always been a concern that once the ester based polymers get saturated with water they all have a significant and immediate drop in strength. Vinyl ester saturates with much less water than polyester but it still saturates. Epoxy saturates at a much lower water level. This is probably the key with the glass bond, water molecules have a peculiar characteristic of accelerating micro cracking. Once the matrix is saturated water is present in the cracks micro-voids and disbonded matrix fibre regions.

    (You even get the same effect in metals, once a micro crack starts and if water is present it doesn't self limit and grows at a much greater rate )

    For example from memory E-glass vinyl ester composite lose a surprising amount of their tensile strength when immersed in sea water after the first year even with an epoxy coating. Used as a barrier coat they slow down the saturation of the polyester

    It's probably not that surprising if epoxy glass has similar characteristics.
     
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