Epoxy comparisons

[Pericles]

Clint,

Stinkier.

As it happens, WEST SYSTEM or any epoxy should not be used in poorly ventilated areas. I would say that the odour is a strong indicator that there could be a problem in the workshop. After all, natural gas has a smell added, so leaks are more easily detected before the big bang.

Pericles

[PAR]

I would like to add that buying pre-thickened epoxy is much less economical then adding thickening agents yourself. Sure you don't have to bother, but you pay for it. I've also found no one filler mixture to suit my needs, which each one being application specific in structural qualities, fairing needs, anti-sagging properties, bonding attributes, etc.

West System also sells duel cartridge dispensing systems, that mix as they come out, to perfect proportions. Not getting proportions correct is purely user error and not following well established procedures, which by nature are user defined. I've been using epoxy for about 30 years and haven't had failures in a few decades. I've a well arbitrated set of procedures I use and I don't deviate from them. Clamps are always where they are at hand, applicators, gloves, jig, release films, etc. all worked out in the dry runs I perform before each epoxy job. The key to all epoxying efforts is setting down procedures that will make success easy to achieve. If I screw up something, it "feels" wrong and I stop and see what I missed, because of the "muscle memory" my body has learned over the years of working goo the same way each time.

There is no such thing as a "safe" epoxy. They all can cause you to have three headed babies, so protect yourself at all times.

[Pericles]

PAR,

Somewhere els,e, hic, I asked if you have a website? I took another gander at your gallery and was delighted to read this:

"It all started with a double ended 34' cruiser with backyard construction in mind for a local bar owner (who turned out to be a real pain in the butt) She was hard chined, has the high chin, tumblehome bow, broken and raised sheer and originally rigged as a sloop, but now a yawl with wishbone booms. The 34 was a well burdened craft, deep bilges and shallow fin/skeg appendages."

That has to be the very best description of a bar owner I have ever read.

"She (the bar owner) has a hard high chin, a tumblehome brow with a broken raised sheer, rigged originally as a sloop, but now speaks with a yawl. She's a well burdened craft with deep bulges, shallow fin/skeg appendages and walks on wishbone booms as if she's got a pain in the arse."

I must stop drinking in the afternoons.:

Best wishes,

Pericles

[PAR]

Lass is the design you're referring and she's quite a gal, though the local bar owner was male and is still a pain in the ass, much like most of my friends.. Nope, I don't have a web site, though this year it seems likely I will. Afternoons are the best time to drink. This way you're primed for the evening drinking.

[Jimbo1490]

For a really high performance resin system on the cheap it's hard to beat a bisphenol f (phenol novolac) resin like Epon 862 or better yet CVC Chemical Epalloy 8220 and a simple amine like TETA. You'll get a mixed viscosity well under 1000 cPs (around 400 with the 8220), an hour of pot life and over 10Ksi tensile strength. Better in virtually every respect than West. And this system has no modifiers to reduce viscosity as the BPF resins are much thinner to begin with than the BPA resin in West, but with more reactivity and lower weight per epoxide (175 vs 190).

CVC is better to buy from as they will sell you a 5 gallon pail without killing you on price too bad. Their products are of consistently higher quality than the 'big three' too, with lower viscosity for products with comparable molecular weight.

An adjustable ratio epoxy dispenser makes mixing all of these 'custom' systems really easy and only costs a couple of hundred bucks.

[cudashark]

OK Pericles,

Here is an update....

[BOATMIK]

Originally Posted by PAR

Epoxy can be formulated to a wide variety of physical properties. The major brands all have similar properties in their standard laminating resins, though there are some differences.

Howdy PAR,

I would agree to an extent if you are comparing "premium" brands.

A decade ago one of the universities here did mechanical testing of laminates using all the common epoxies available at the time.

I think a total of around 12 different types.

The top three or four "name" brands all did pretty well with a good balance of tensile strengths, elongation et al.

But then there was a huge drop in performance as you moved to epoxies that were sold on price.

They were well down on all mechanical properties - and I am not talking 5 or 10 percent - more like 50 to 60 percent.

This was borne out in a later series of tests using steel balls dropped on epoxy coated pieces of ply from a consistent height.

The quality brands ended up with fractures only in the area the ball contacted. Some of the poorer quality ones looked like broken windscreens on a 1960's car.

That data is now pretty old - but my personal answer is not to skimp on the epoxy quality and be prepared to pay the full price and I would never buy epoxy from a company that doesn't do any research or testing of its own or is significantly cheaper than the market leaders.

There is one specific hint I would like to put forward. If you buy a cheap epoxy and it smells of thinners - then it is going to be structurally very poor indeed.

The quality boatbuilding epoxys are all "high solids" which means little or no thinners used in the ingredients or processes.

A little ammonia smell is fine - but any epoxy that smells of thinners should be avoided.

Interesting stuff from Jimbo too.

Best wishes
Michael Storer.

[Jimbo1490]

Not all of the thinners have a detectable odor, though certainly some do. Several of the thinners (reactive modifiers, more accurately) improve elongation and fracture toughness, though at the expense of high temperature service and reactivity. West is *allegedly* Epon 828 and one of the reactive modifiers.

All of the reactive modifiers become part of the cured mass, that is they do not evaporate out before cure like the solvent in an epoxy primer or paint, for instance. That being the case, resin systems that contain reactive modifiers are still considered "100% solids" formulations.

[Jimbo1490]

A quick review of their literature reminds me how much the properties of an epoxy resin can be improved by the addition of one or more reactive modifiers, at least for the 'simple' resins like plain ol' bisphenol A, EEW 190 resin (like Epon 828).

With the addition of just 10% diglycidyl ether of neopentyl glycol (Heloxy modifier #68) the viscosity of 828 goes from ~14,000 to around 1400 cPs (just like West....Hmmm ). Yet UTS, elongation and fracture toughness all improve. Only Tg and reactivity gets worse. The loss of reactivity is not a big deal either since a >10% adjustment in mix ratio by way of adding more curing agent makes up for the loss.

This has the hidden benefit of reducing viscosity of the admix further, since the curing agent is way thin. This is how you get from ~14,000 cPs (VERY cumbersome to work with) all the way to > 1000 cPs (Just like West...Hmmmm ) and with mosly better cured-state properties.

Now it's a different situation with the phenol novolac resins like Epon 862. They are already pretty thin, > 3000cPs before catalyst. With their higher reactivity and better cross-linking, you have more 'excess' properties in the form of UTS and Tg to trade for better handling (low viscosity) and you don't need much modifier to get there.

The Epon starting formulation for a hand layup aerospace resin used Epon 862 with Heloxy 68 @10% and Epi-Cure 3234 (TETA). The mixed resin was WAY thin, like >400 cPs with high UTS yet with outstanding fracture toughness, and 9% elongation(!). With a post cure Tg was around 200 F. About the only negative is the very short pot life of only about 30 minutes

[BOATMIK]

Good point about the reactive modifiers Jimbo.

I wasn't sure whether I should go there.

However I think most of the low quality epoxy producers will go the cheap way with thinners too and use more conventional ones.

Cheers
MIK

[Pericles]

Cudashark,

Beautiful lines and excellent work. Where do you source the timber?

It's getting more and more difficult to find decent wood in the UK, although that is not the case for BS1088. S&G techniques would seem our way forward, I guess.

Thanks for the photos,

Pericles

[cudashark]

Thanks Pericles,

Thanks for the compliment.

Here in South Florida mahogany ( South American ) runs 7 dollars US a board ft and African mahogany about 3.80. Douglas Fur no problem and several species of cedar are also abundant; we even have a beautiful domestic quarter sawn white oak supply.

Timber is pretty abundant and if your interested in importing a container or two I have the contacts for you.

Ray

[tommyboat]

I have used several brands and did my own tests which the scientists would say is anectdotal however did not found much difference for my application. Currently using the epoxy from bought on Ebay from that guy in San Diego think his name is John Greer.