Reducers or Thinning questions

Discussion in 'Boatbuilding' started by Dave70, Oct 17, 2010.

  1. Dave70
    Joined: Oct 2010
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    Dave70 New Member

    Hi all

    This is my first post but have been reading loads of the forum here. good stuff.

    My main question would be about thinning resins or paint.

    Is paint or gelcoat different then simple poly resin or epoxy out of the can ?

    everything i find for paint or gelcoat or even latex says to to thin it depending on how im going to apply it.

    then i look and find that when you thin your going to drastically change the quality of the resin or paint ?

    So should these paints or resins be thinned or unthinned. or is it a matter of what product is developed to be designed to be thinned or not.

    example that awl grip has to thinned.

    Im trying to update my product know how and im not new to poly or epoxy by any means.

    but it seems like there might be different answers to different products?

    thank you for your time and hello once again :)
     
  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    If you are talking about paint, then yes, thinning is permitted and usually necessary.

    Epoxy resin, used in laminating, bonding, etc. isn't generally thinned, unless you haven't a clue about the chemistry you're fooling with, but polyester resins, used for the same reasons usually are thinned.

    So, define your questions a bit; paint or laminating? Epoxy, vinylester or polyester? The resins systems used in both paints and laminating, are treated very differently and though some techniques are the same in application, the chemistry and mixing requirements are very different among them, which is why we need further definition from you.
     
  3. Dave70
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    Dave70 New Member

    I know for lams you dont want to thin at all. I know this. It is not needed nor desired so why do it.

    Basically my question is do you have inherantly different qualities in the BASE of the resins .. Epoxy or Poly ?

    Lets say epoxy primer compaired to epoxy resins. Is there a difference in chemical makup between the two that one has to be reduced for application and the other cant be reduced at all without serious detriment to the end crosslinking.

    Or Poly resin to gel coat. Am I to assume that I cant reduce gelcoat for full spray application because Im going to need to reduce for spray without having serious consiquences on the chemical makup of the resin. Or can I reduce Poly resin somewhat without the same results.

    IS the base resins for lams or Paints/topcoats/gels the same base resin for each ? If so then why are there do's and dont's for each application.

    Im just trying to get an answer on why small reduction for epoxy or poly lam resins for specific applicatiions are a REAL bad thing when there sister resin based paints/gel need reduction without quality loss.
     
  4. Landlubber
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    Landlubber Senior Member

    Dave, Maybe you do not realise that epoxy paints are not actually expoxy paints (as we know epoxy for resin, compared to epoxy for paint). It is a term used by many paint manufacturers to describe their paints, but they certainly are not of the same family as epoxy resins for laminating. I am sure that one of our chemist mates here will explain for you, maybe PAR knows thae answer without doing a Google search for it.
     
  5. PAR
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    PAR Yacht Designer/Builder

    Dave, again, I'm not sure if you are discussing paint or resin systems. This is the first question, which do you need answers for?

    Second, epoxy and polyester are greatly different chemically and nothing about either is interchangeable. They also differ considerably physically.

    Simply put:
    No. I know of at least 6 different resin bases for epoxy alone. Now, this said there are only a few that are very common.
    Yes. There can be considerable difference among the epoxies, but much more so among the polys. The resin systems among the polys is very diverse and going into the chemical differences here would entail a literary volume.
    I'm not sure what you mean with "sister" resins, but I suspect your understanding of these resins is causing the majority of these questions.

    Maybe it would be helpful if you just told us what you were attempting to do, with specific questions to specific issues you are encountering. The reason is this isn't the best format to improve your general knowledge on a wholesale level about any specific subject, but it is a good place to get answers to specific issue questions.
     
  6. Dave70
    Joined: Oct 2010
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    Dave70 New Member

    Thank you for your replies.

    I just did not want to start another heated debate on thinning resins.

    I was going to poly resin coat some regular plywood for a plug and mold. But I wanted to thin the first few coats of resin a little to soak into the plywood so my mat had a bit more bite into it.

    I dont really care much about the plug after the mold was made. I do want the mold to last for some time.

    But after reading some postings and threads here about dos and donts I didnt understand why its a bad thing to reduce the resin when I have to reduce my gelcoat sometimes.

    Thank you again.
     
  7. apex1

    apex1 Guest

    For a one way item like a plug, you even could use thinner in Epoxy. Though thats not sensible in this case. Thinned poly does the trick.

    Regards
    Richard
     
  8. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Now that you've made some clarification yes, it's desirable to thin poly resin for the first coat on your wooden mold. It'll improve it's grip on the plywood.
     
  9. Herman
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    Herman Senior Member

    What will you thin it with?

    Polyester can be thinned with acetone or styrene.

    For basic knowledge:
    The acetone needs to evaporate from the resin, leaving it more or less porous.
    The styrene basicly stays in the resin, there is already a certain amount in it (approx 35-50%). It co-cures with the polyester resin, although an amount evaporates as well. (generally 7% or so, but it can vary).
     

  10. Dave70
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    Dave70 New Member

    Thank you All for the replies.
     
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