Effect of humidity during laminating

I am building a foam glass epoxy boat and struggle with high humidity levels almost all year round. Resin supplier specifies 70% RH max but is unable or will not tell me how much of a detriment higher RH during lamination is.
I have tried searching BD forum and the internet but have not been able to find an answer. There is information on long term effects of humidity on laminates but not on effects of humidity during processing.

My understanding is that there are two issues at play.
1. Co2 and moisture reacts with the amine hardener and is mostly a surface issue that can be dealt with by the use of peel ply. Also one can choose a hardener with lower blushing tendency and faster gel time.
2. Fiber to resin bond/interface, high RH during processing lowers the fiber to resin coupling strength. Which leads to lower strength laminate.
But how large is the RH influence? has any one seen any test data that quantifies %RH during process with laminate strength?

If the fiber resin interface is the main issue then the cheapest way to over come this may be to have a climate controlled room/tent in which the reinforcement can be wet out with resin and then carried out and consolidated on to the structure out in the workshop.
Is this a valid assumption?
OR do I really need to climate control the area being laminated in situ.

Regards
Andrew

 

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I expect a lot of good advice on this has been wiped with departure of one of the knowledgeable members.

The amine blush is certainly an issue and if you do not clean it well then the subsequent bond will be poor. The best is to wash before you sand. It will blind sandpaper and be worked in rather than cleaned off.

Infusing will draw a lot of moisture out before the resin gets in. There is some really impressive work with infusion but takes a good deal of knowledge and experimentation.

Peel ply certainly overcomes the blush problem.

Epoxy is water soluble until cured so it may be compatible with the epoxy if only surface moisture.

You could do your own test. Saturate some cloth and do a layup, Compare same layup done in heated room. I would be interested in the result.

I wait till winter before I get into making things that have a bit of value and then use a some heating to get it nice and warm as well as dryer. But I am in Melbourne. Sounds like your are in Northern Queensland or other tropical region. Do the bulk of the work in the dry season!

Rick W

 

Epoxy is water soluble?

 

I gather they vary. But they turn cloudy if wet and you can clean up with water. Have a look at the MSDSs. Most say ay least Slight solubility in water.

It is one of the good features of using epoxy over polyester.

Rick W

 

Hi Rick, I am on an acreage surrounded by large trees on the north side of Brisbane.
The local micro climate is more humid than suburbia just 5 minutes up the road.
This is one of the reason why I have been using infusion for all large laminations, but its not practical for smaller jobs and you still need to do a lot of taping in situ.

I was hoping someone can point me to some reliable test data rather than anything subjective that I can do. It must be available as where did the 70% max RH rule come from?
I am also guessing that this decoupling of resin and fiber happens with load cycling so may not show up with a simple bending test that I can do.

I am an ex Melbourne person and I would much rather be building in composites there than Brisbane.

Cheers
Andrew

 

Andrew
I consider epoxy layups to be similar to welding. If you are designing to tight margins then you need to proof your specific process in the same way as you would for a good quality weld. I also suggest you take test coupons for later testing.

I have seen wide variation in test results for what is notionally the same layup. The better you can control conditions the better the result.

It is not hard to do high cycle testing with a little electric motor in a couple of days if that is your concern.

If you want a quality job you need to proof YOUR processes. It is no good relying on data produced by others. It provides a guide but not reliable in your case unless the process is identical.

I have seen very wide variation in carbon fibre layups. A small crease in the cloth that ends up with a slight misalignment of fibres in the layup reducing the compressive strength to a fraction of what it should be.

I believe there are a few boats built in places like Mackay that have to contend with high humidity. Maybe they are to be avoided.

Rick

 

Rick, I agree with what you are saying.
I keep hearing about the very large variation in test results for same layups, but no one ever shows the results. Having said that it is not surprising as the observed quality of workmanship is so variable. But this is not what I am asking for.
In the case of relationship of humidity level during processing and laminate quality the laboratory data that lead to the 70% guideline is far more accurate than what I could do. And it is universally applicable to all.

 

Andrew
This link will go to a paper that discusses layup issues:
http://www.coe.montana.edu/composites/documents/AIAA_2004_0174.pdf
It has nothing to do with humidity though.

I can find links that discuss humidity but I could not find any that are free and it is not certain from abstracts if the results are relevant to your case of humidity before and during curing. There are a few references for looking at humidity and temperature in operation.

There are also reference to additives that improve adhesion with high humidity so it would seem humidity is detrimental but how much I do not know.

The polyurethane glue and paint I use both rely on humidity for curing. So the moisture is an advantage there.

You may find something on supplier sites like this:
http://www.epicresins.com/

I get some materials from FGI and they manufacture here in Melbourne. They are part of Hunstman Chemicals. They will have chemists on the plant. They may have a technical specialist who can advise on the consequence of humidity during curing. So an option if there is nothing useful coming along here.

Let us know if you get any information.

Rick W

 

Thanks Rick I will let you know if I find anything of use. I found FGI in Brisbane very poor for getting any decent technical information from. I have also been told that they do not manufacture (blend) their epoxies and recently have been given a contact for the manufacturer, Hiltour Resins.

 

Andrew
I have checked on FGI. I believe they are owned by Nuplex not Huntsman. In Melbourne they operate from what is or was a Huntsman site. I am not up to date with ownership.

I have been advised there is some technical support in the Wacol office of FGI. Maybe they can help.

Rick

 

Humidity affects curing speed, it speeds the resin. Also, you could run into an issue with bubble formation. (do a test, and mix in 5% water in a small batch of epoxy resin, this will dissolve completely.

However, I do get more worried about the effects on the glass and the sizing. I have some customers that claim a better adhesion and less resin consumption when the fibers are completely dry, and therefore have their glass in an oven (70 degrees C, or low temp sauna).

The 70% rel. humidity issue is because at that level you can about guarantee that no condensation can occur on colder objects (your glass fabrics)

 

I have read that glass sizings are hygroscopic so will be absorbing moisture even when the surface temperature is above due point.
When I fitted out my current boat I used the shiny metal surface guideline. You lightly breath on a paint scraper and as long as the condensation evaporates within 20 seconds the humidity level is OK for glassing.
Maybe I should just toss out my humidity meter like most builders around here.

 

The rep at Nupol said they are the 'old' Huntsman

FGI are a distributor for Nupol I understand.

So far, Nupol (in melbourne at least) have been good at getting me info.

 

RWATSON, thanks for that, I was aware that GFI & Nupol are part of Nuplex Industries but trade independently.
Can you ask your contact as well please as so far I have left two telephone messages for the fgi chemist, sent an email to Vee-Tek (manufacturer of fgi epoxy), West System and copositesworld.com. Unfortunately I have had no response from any as yet.

 

I have spoken to :-

Daniel Chatley
and

Leanne Williams
Customer Service Co-Ordinator
Nupol Composites
Leanne.Williams@nupol.com.au
ph (03) 9555 6711
fax (03) 9553 3525

They are located in Melbourne

I dont know if they are close to where you are or not.

Good luck.

I get the impression that sales reps etc for composites, are often so snowed under they put you on a "low viscosity" list and have to be stirred vigorously to get activated again. I got "bogged down" by a few queensland firtms before I found a local supplier I could visit