Barrier coating behind the gel coat tell me please !

Discussion in 'Fiberglass and Composite Boat Building' started by tunnels, Feb 12, 2011.

  1. tunnels

    tunnels Previous Member

    Hello
    Have been hearing a little about barrier coats behind the gelcoat .
    any one use them and whats your opionion ??
    whats good and whats not so good about them ??
    What about below the waterline of big boats ?
    water absorbsion ????
    They use a special catalyst?
    what if you dont use that but something else ???
    :confused:.
     
  2. jiggerpro
    Joined: Sep 2007
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    Location: spain

    jiggerpro Senior Member

    To me, those miracle products " sound" like another good way to steal away some more money from the composite builders with stories built by vendors to fool purchasers, something quite common nowadays ............ even among medical doctors at least here in my country Spain, where morals and ethics where forgotten long time ago

    The ones I have read about are not for use under the waterline
     
  3. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Many of the barrier coats work quite well, the problem is they frequently are used incorrectly or in the wrong application.

    Decide what you want the barrier coat to do, blister resistance, print blocking, air bubble prevention, stiffness, speed production, or all of the above. Then decide how good of a job you want it to do and how much you're willing to pay for that performance.

    Don't buy a low cost print blocker and expect it to stop all blistering when a cheap resin is resin behind it, or a stiff brittle ceramic filled product on a flexible panel.
    These types of practices can give a class of products a bad name, just like the core mat from your other thread.
     
  4. tunnels

    tunnels Previous Member

    Yeah got ya and just like i thought ! So many places use products the way they were never intended or they exspect a mircal and it dosent deliver when in reality its all comes back to poor workmanship and choice of materials in some cases .
    The big thing in asian countries is shine and gloss and sparkle! performance and how good the boat goes almost takes second place .. Ever since i arrived here i have been bomb-barded with we should be using Barrier coat behind the cel coat . The only time i have used Ceramic coatings was on a big hull mould but at the end of the day it looked no differant to any other mould that was made ! two years later it had the same kind of mark's showing through that you could find on any other mould .
    I have noticed as time has gone by products are becoming less forgiving than the older ones we used . We always hand brushed gelcoats and never had one issue of any sort , then we started spraying and a whole raft of problems appeared and the same problems have persisted with us no mater where i happen to have gone . Be it a pressure pot or airless spray its really up to the operator and the guy holding the gun as to how good the job ends up . Same with the first coat of glass that goes on behind the gelcoat and the a quicker brew of resin and lots of it coupled with lots of care and attention to detail was always given and again hardly ever a problem . Cure of products these days is all important as they are more tempramental and far less forgiving !:(
    So in reality Barrier coats are just another way of covering poor workmanship .:eek:

    :p:D:p
     
  5. jiggerpro
    Joined: Sep 2007
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    Location: spain

    jiggerpro Senior Member

    Hi Tunnels, as I am also investigating the subject of barrier coats, I found one that might be good, it is named "Atlas E-coat 65" it is made by DSM and the manufacurers claim that is an excellent barrier for the prevention of osmosis ( being made with vynilester), they even claim not to be compulsory the use of any application of CSM behind the barriercoat thus eliminating the man hours needed to laminate it but they do advise that to get the best results some CSM should be used ......... it seems like a good product to me because it serves two purposes contrarily to others: a good protection against blistering so it is advised to be used below the waterline and also the cosmetic anti print thorough properties
     
  6. tunnels

    tunnels Previous Member

    Thank you for that We use DSM gelcoats and about to do a deck in the next day or so . Will ask the question of our local rep and see what he has to say !!:p
    Thank you for that snippet of info !! :D
     
  7. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    We have been selling ITW Spraycore barriercoats for a couple of years, and switched to Nord Composites barrier coats after Euromere took over ITW Spraycore. (in Europe).

    When doing it right a barrier coat does help improve cosmetics (less print) and does improve resistance against osmosis (I still have samples from years ago in my accelerated osmosis tester, that just refuse to develop any sign of osmosis).

    Most barrier coats are vinylester based, and need a special curing agent (hydrogen peroxide free) to cure trouble free.

    In the years I have experienced (not related to barrier coats) that production companies are seldomly willing to follow manufacturers procedures for using new materials, thereby compromising good results.
    In the case of barrier coat, this is:
    -too thin gelcoat
    -not using right peroxide, thereby creating porosity due to formation of gas
    -not obeying overcoat windows
    -not checking wet film thickness
     
  8. tunnels

    tunnels Previous Member

    Hello
    Thank you so much for all that !! Its really what i had throught anyway .
    So its ok to use below the waterline !! This was one thing no one was able to tell me .
    Years back i used Ceramic fortified backing coat . Personally couldnt see any differance from using and not using it , not even after a year .
    I totally agree with what you say about using product correctly and having the same problem right now with Catalyst being used for Polyester resin and the same for Gel coat and it takes a hell of a long time to gel and go hard . Like 2 hours to gel and a good 3 hours plus to go hard !!
    Have been shot down by everyone including the chinese DSM reps and there technical people here . First place in the world i have encoutered this . Cant remember the brand of the catalyst , number is M 50 all year round for everything anytime of the year winter at -5c to what ever there summer is in the high 30C S
    Have managed to get a sort of a hot room but 12.5c is all i can get so far .

    The thing of never using a wet film thickness gauge has caught them out on 3 decks so far with thin patchs and patchs of alligation when it was finally demoulded . :D
     
  9. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    M50 is Butanox M50, a product by Akzo Nobel. This NEEDS 15 degrees C to cure properly. Anything below is not a good idea.

    Unfortunately I have no idea of what is available in your place. There is more than M50, the company I represent in NL (Norac Andos, now called Syrgis) have plenty of choice, including special peroxides for gelcoats, leaving less porosity and giving a good cure.
     
  10. tunnels

    tunnels Previous Member

    Thats the one ! I do realise the heat and the differant Catalyst thing . Our factory manager is not a glass person and he relys of his own people to tell him whats good and hot things are meant to be made . What i say falls on deaf ears . But as i say i cant wait to make a big boat because no one has any knowledge about laying glass other than woven and chopped strand . :(:p:D
     
  11. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    The blistering is usually on the gelcoat. It doesn't make any sense to put the protection behind it.
     
  12. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Blisters are most frequently found in the laminate itself, the second place is at the interface of the gel coat laminate, third is in the gel coat. Gel coat is blamed for blistering due to it being on the surface and that’s where you see them.

    The correct barrier coat used correctly can almost completely eliminate the blister issue.

    Straight VE barrier coats do a great job at blocking print from fabric and preventing blisters and cracks. As you add fillers the print blocking ability typically goes up, but there can be some trade offs in blister resistance, depending on the filler crack resistance may be hurt also.

    Straight VE's will block about 80% of the fiber print, maybe more when used with the correct resin, fillers help to block even more. Highly filled products can block virtually 100% of the fiber print and most of the core and/or bracing print.

    This is all based on using each product correctly and in the recommended environment.
     
  13. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    That is not according with what the general experience in the industry is. When you remove blistered gelcoat, there is usually good laminate under.
     
  14. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    Check the recommended methods for repairing a blistered hull, once the gel coat is removed what you most frequently find is a blistered laminate that needs to be peeled too.

    We've done thousands of blister tests for customers and while we can make gel coats blister, the results of the test typically depend on the resin in the laminate holding up. A good barrier coat can stop almost any resin from blistering.
     

  15. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    I don't agree with that. It is a very rare thing to find a laminate that needs to be ground or planed and then re-laminated. What kind of boats do you survey or repair?
     
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