Epoxy V's Vinylester Infusion

Hi There,

We currently use a vinylester tie layer and a the vecuum infuse epoxy. We were thinking about changing to Vinylester infusion. I know epoxy has superior water degridation properties but not as bad as polyester. I also know that there is more shrinkage associated with vinylester but this shouldnt be too bad as we have a tie layer of vinylester so you would think shrinkage would be similar. I know that the strain to break is not as good with vinylester but this shouldnt be an issue if you are sticking to calss society rules as they have a limit to deflection and looking at panels which scrape through the rule, the strain is nowhere near the 2% limit for the least flexable vinylesters.

Is there anyone who has experiance with Vinylester infusion? Is it hard to get the mix of catalyst to get the vioscosity correct throughout the infusion? I guess it depends on the temperature of the environment. Is this the main drawback of Vinylester over Epoxy?

I appreciate any views on the topic

 

Vinylester will likely gel and cure faster than epoxy depending on your part size, and whether you're using any elevated temp post curing or such. They do make a specific MEKP for infusing that takes longer to initial gel. You may need more resin feed lines, a low visco version of vinyl designed for infusion or other adjustments depending on the part size, temp, and typical infusion time. If you're using core materials see if Diab can help you out. Their eng staff is great for specifics on infusion with various resins and specific core changes to optimize it all. If you're single skin can your resin supplier provide any support? Your regional Composites One should be able to recommend specific products, especially since you may be able to send info on viscosity, kick time, and such from the past epoxy infusions. Most infusion I mix the resin/mekp in a bucket or barrel and then suck in, and with the proper catalyst and resin there's no problem with viscosity changing before the parts fully infused, but then I'm also doing smaller parts (less than 150sq ft).

 

If you are already used to infusing epoxy, the change to vinylester is a simple one.

Are you in the USA or in the UK?

Get a good quality vinylester resin, low shrinkage and low viscosity. Make sure it comes unpromoted. Also get cobalt octoate (preferably 6 or 10% mixture) and the right catalyst/MEKP for the job. Regular MEKP will not do the job. There are types that have long open time, but still a very good final cure. (mostly even better than normal MEKP).
Something to watch for is getting a H2O2 free catalyst, as H2O2 will react with vinylester, and cause foaming. There are a couple of Norox (Syrgis) catalysts that do the job well.

When infusing you will notice that if you have a nice low viscosity vinylester, the infusion will go slightly faster.

Before the infusion make a series of tests, with different amounts of cobalt and catalyst. Your supplier should be able to direct you into the specific amounts. This will give you the information needed to get the right geltime.

IF you need to add retarder, this usually is done in 0,01% increments. Mix a small batch of resin with retarder at 1%, then mix this resin into the batch-to-be-tested at 1%. Now you have reached a 0,01% level without spending a fortune on highly accurate scales.

So basicly VE infusion is the same as epoxy infusion, with the difference that you have more control over the geltime of the resin. Which makes long vacuum times obsolete. However, more control means you need more knowledge of that specific resin.

Doing the same part over and over again, will give you the opportunity to design the VE for the job. Keep a log of what you are doing, so you can learn from it.

Also VE resin can differ in curing speed from batch to batch. So make a test of each barrel, to see if they differ from each other.

 

Vinylester infusion

Like most things with composites, the answer to that question is not a simple one. There are several Vinylesters that can be used for infusion that have elongation of about 9% when they are cured. We are using one ofthem right now for infusing all of the parts (hull, deck, structure, bulkheads, etc) and don't have any shrinkage issues. The lack of shrinkage is due to the curing system we are using. We promote, and inhibit, the resin ourselves, and then use a CHP blend as the catalyst. We can control gel time between 30 minutes, and 240 minutes, the part during cure never goes over 95F, and we still get full barcol and have no issues with HDT after cure. There are several very good vinylester resins that are available. We are using one of them from DOW (they have several). AOC has another one. Talk to your vendor, and do some experimentation.

 

Guys,

Thank you so much for your time. You have all given me plenty to think about. I am based in the uk. I think the answer is testing and making sure the batch we are about to use has also been tested.
I am thinking DSM resins. Has anyone had experience with these?

 

Bilf. PLEASE - at the highest level of importance - consider the increased level of carcinogenic dangers of vinylester resins. Significantly higher % wise than the other polyesters (ortho or Iso) &/or all of the epoxies.

Before instigating a change in your production proceedures PLEASE go & consult your 'Plastics' Work-place, Health & Safety Doctor.

Then - DO NOT USE 'VINYLESTER RESINS'. I banned the use of it in my factory over 30 years ago. Whilst it may be a 'GREY' area - my staff was far more important than playing in a GREY AREA.

Do have great fortune in 2012 - with your business decissions - make them very carefully. Ciao, james jackson. Cairns, Queensland, Australia.

PS Much higher levels of cure can be obtained by changing the 'catalyst/s' being used & some heat cure as well. jj

 

It is an infusion, so very little exposure to any resin. The mixer could be in a supplied air tent or wearing a supplied air suit.

The others just run the valves and what not.

All vinylester fumes go out through the vacuum line to a vacuum pump that should be vented outside anyway.

 

Can you back that up by something scientific? The problem chemical in vinylester is styrene, which is also in polyester, even in larger amounts.

Styrene levels over the years have dropped considerably, from some 60% to now between 30 and 40%, or even dropping below 30%.

Infusion cuts the major amount of styrene evaporation, which when hand laminating can be as high as 10%

 

Wonder if the vinyl disliker is from the marine industry or fully understands the product benefits it can have, like in some instances survivability of the vessel in extreme conditions resulting in likely survivability of the boat's occupants. With modern resins can come a requirement for modern safety gear beyond a basic respirator, and then there's the whole thing about Infusing. this isn't chopper gun layups...

 

Material Data sheet

http://www.epoxysystems.com/msds/85MSDS.pdf

Carcinogen = YES

 

Fiberglass (just the glass) is now listed as a carcinogen as well.

Pretty much all of this stuff is bad for you. It's a price we pay to build boats, I guess.

I have accepted the possibility of an early death from it.

 

rwatson: That is the styrene. Which is not specific for vinylester but is in all polyester and vinylester. It does not rule out vinylester infusion.

Catbuilder: can youback that one up? My MSDS tells me different. However, any fibrous stuff being pumped into your lungs is dangerous. Even cotton fiber.

 

I couldnt build much in VinylEster no matter what is in it - it just plain STINKS !!!

 

Herman: I have been trying to locate it, but some dept of the US government, possibly 3 months ago, put fiberglass on the "carcinogen" list. I read it in the news and don't seem to be able to find a link. If I come across it again, I'll post in the source. To be honest, I tried to forget about it! ha ha ha