Vinylester question

Hi

I've tried to gather info about Vinylester. I know of projects using it w. handlayup and no hightemp curing. On the net I've read that to get the most of vinylester it needs heat during curing.

Since I'm trying to gather information for my first larger project I've decided that the difference in cost between the available resins Vinylester seem to be the choice for me. But does it have the extra qualities I'm seeking (water restance and strength) if I don't use heat for curing.

How des the temp affect the material?

Anyone with good information?

Thanx

[Jeff]

I believe that without a postcure Vinylester will still offer you slightly better adhesive properties and possibly more importantly higher resistance to osmosis than polyester resin.

A nice starting reference is this PDF available from SP Systems:

http://www.spsystems.com/pdfs/SP%20G...%20Systems.pdf

or http://www.spsystems.com/prod-formprod.htm

Vinylester resins are similar in their molecular structure to polyesters, but differ primarily in the location of their eactive sites, these being positioned only at the ends of the molecular chains. As the whole length of the molecular chain is available to absorb shock loadings this makes vinylester resins tougher and more resilient than polyesters. The vinylester molecule also features fewer ester groups. These ester groups are susceptible to water degradation by hydrolysis which means that vinylesters exhibit better resistance to water and many other chemicals than their polyester counterparts, and are frequently found in applications such as pipelines and chemical storage tanks.
...

With the reduced number of ester groups in a vinylester when compared to a polyes-ter, the resin is less prone to damage by hydrolysis. The material is therefore some-times used as a barrier or ‘skin’ coat for a polyester laminate that is to be immersed in water, such as in a boat hull. The cured molecular structure of the vinylester also means that it tends to be tougher than a polyester, although to really achieve these properties the resin usually needs to have an elevated temperature postcure.

Two important mechanical properties of any resin system are its tensile strength and stiffness. Figs. 12 and 13 show results for tests carried out on commercially available polyester, vinylester and epoxy resin systems cured at 20°C and 80°C.



After a cure period of seven days at room temperature it can be seen that a typical epoxy will have higher properties than a typical polyester and vinylester for both strength and stiffness. The beneficial effect of a post cure at 80°C for five hours can also be seen.

* From Guide to Resin Systems for Composites by SP Systems at http://www.spsystems.com

[stephan shugart]

I found a wonderful web site at WWW.netcomposites.com They have all the answers it seems even broken done into chemical formulas. It is beyond my knowledge but it seems to help me understand.

I have been looking for such a website myself since I have undertaken the quest of building a sailboat of my own. I am just about as confused as it is possible right now. I read one article on composites for example and how they are so great and then I read David Pascoe article on composites at WWW.yatchsurvey.com and I get the tar scared out of me and then I don't want to look at a piece of foam at a 100 yards.

I guess he is right though. What has worked for 40 years should'nt be changed just because foams are in vouge now.

God Bless All, Stephan

[Tim Dunn]

Re cores: Well, if you are using a female mold with a hull having compound curves (ie round bilged, not hard chine,) it is hard to know whether the core is bonded, or not. There doesn't seem to be any problem with balsa and decks, which is the usual method of making fiberglass decks. But, decks don't have much curvature, especially much compound curvature.

Re vinylester curing temp: Does this difference reduce over time? 176 degrees farenheit (or so) is a pretty high temperature for a boatshop. Talk about a sweatshop. But hey, it isn't the heat, its' the resin fumes, right?

[War Whoop]

Interplastic has a nice site where a lot is explained on/with real time vinyl ester testing and its long term exposure longevity Btw Stephen there is only one Foam Core to use…. and that being Core Cell ! while we are on Foam.

The Polyurethane foams are like useless on peel strength unless you reach the weight of Granite.

Airex is good foam I like it a lot; but it has thermal considerations.

The PVC blends are a little brittle trade-offs (the Polyurethane again) and in the lighter densities can have a styrene problem with Well !! some poor shop practices.

The non rated materials like Mantex Who would use such a thing? Get this they offer a 5 year warrantee on the material. Then What??

This Rant was the commentator and not the station.

http://www.interplastic.com/html/technicalpapers.htm

[ErikG]

As War Whoop mentioned Core Cell has been recommended to me by more people than any other core. SP Systems also recommends Core Cell for theur products incl. the prepregs.

UNFORTUNATELY... ATC the makers of Core Cell have filed for the Canadian version of chapter 11, hopefully soe other company will buy them so the production can continue.

ErikG

[War Whoop]

Erik The filing is not really as it looks! They are going to be around for a while.

[tgundberg]

MY guess is ATC filed chap 11 so it'll be easier for a larger composites group to buy them out...time will tell. As for corecell being "perfect" I definitely disagree. The only reason SP is favorable of them is because they are a distributor. Then you have issues such as styrene resistance, notch sensitivity, and flame spread..

As for Pascoe, I'd take everything he says with a grain of salt. He's a surveyor and I bet has never seen let alone built a boat before. As for foam cores, they have been around for over 30 years now..so much for "in vogue".

[ErikG]

Trevor I agree that Core Cell is not the only foam to use.
But the production methods I've been looking at, use epoxi pre pregs, it looks like they might be a little bit more usable in sheet form than yours. Divinycell on the other hand is not a bad foam at all, and i would probably not use Core Cell for anything with a high styrene content that's true.

[tgundberg]

I agree, there are some issues with some low temp cure and long out time prepreg materials and PVC foam. I believe it has to do some of the additives in the resin (catalytically cured epoxies) not being compatible with the PVC chemistry. The one guideline I can present is to be wary of long out time (+14 days) and low temperature cure (<200F) prepregs with PVC foams.

On the other hand, there are alot of epoxy prepregs that do work with PVC foams. The 200F+ cure prepregs work fine with PVC foam. Prepregs from Cytec, Fibercote, ACG, etc. all have good track records with PVC foams.

[War Whoop]

Tgundberg I would think just the opposite would be true and the reason on the 11 issue...

ErikG what then would be your personall choice for foam core in say a highly stressed lightweight structure (the complete Deck & Hull Shell) like a Race boat such as an Offshore Powerboat?? Just asking!

The styrene issue is more related to... I would think stupid people than the material really! Get this …what kind of a dumbass would allow the material to soak for hours and hours in a world class Solvent?? And secondly even more bazaar and mind boggling doing this all without the benefit of TESTING!!




But as I mentioned it is all from the neck up.

[tgundberg]

I don't think any one allows core material to sit "hours and hours" in uncured styrenated resin. Styrene attack on Corecell can happen well within an hour. If not, then why does every Corecell application guide require hot coating ever piece of foam before applying any fiberglass? Also, in infusion processes low viscosity resins can have gel times in excess of 1 hour. What does the Corecell do then? Try it out and see for yourself.

As for notch sensitivity I have test results from ATC themselves, and I'd like to see Corecell pass an FAA vertical burn test..

[tgundberg]

One more thing I should clarify, PVC foams work well with most prepregs with cure temps from 200 to 265F (High Temp foams). Don't try to use prepregs with any foam (other than PMI or maybe some urethanes) over 280F for extended periods of time (depending on density and core thickness).

[War Whoop]

My main Question to you Guy’s was which …. Foam…. Would be better to use in a light Offshore Powerboat in racing conditions than Core-Cell or even Airex?? A simple question ….But I got ALL but that!! BTW Aircraft do not fly very far when they hit the Water!! Just thought I’d let you know.

Now What kind of a Foam Core material would you recommend? From your experience as a Boat-Builder...Which should include the racing.

I await this revelation! Also I have seen everything tried and Know what works!

[War Whoop]

As for notch sensitivity I have test results from ATC themselves, and I'd like to see Core cell pass an FAA vertical burn test...

By Tgundberg
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Wow!! Tell you what I'll just pass that juicy tidbit on to some of the high end Boatbulders that should really Rock their engineering Depts and then the Ones Like Merritt for a example...(they are a Divinicell dealer no less ) And look what they Personally use---->Corecell in all those beautiful Mega Buck Sport Fisherman..

Seems like anyone who is somebody in this business uses Core cell from high end Yachts to High Preformance to Fly Fishing Skiff's. What gives??

Still waiting for a core suggestion..A Clue offered here No Brittle Crap!! Need to keep the customers alive!!