Thread: Megapoxy

Hi Zore and all,

I have heard of Megapoxy, but haven't used it. The things I know about trying new epoxies are.

1/ It needs to be a "high-solids" type - this means no solvents have been added. If solvents have been added then the epoxy will not prevent the water from getting into the timber. If solvents have been added you can often smell them. Epoxy shouldn't "take your breath away" when you smell it - though the hardener might have a slight ammonia smell.

2/ Ratios - at this stage the chemistry of economical epoxies requires that they not be a 1:1 ratio. 2:1, 3:1 etc are all fine. I know that there is one knock down price "epoxy" sold in the USA that requires only a small amount of hardener - like 1%. That is not epoxy as we know it, Jim

3/ Price - Epoxy is expensive to make - so it will never be really cheap. If it is really cheap (and is not on special or being used as a price leader - if it is buy the epoxy from the shop but check carefully the prices of everything else!!!!) then it is likely the quality has been compromised. It might be possible to get the price down 10% but a price of 50% less will usually mean that something has been messed with. Not necessarily - but possibly.

4/ Premixed/Gelled Epoxy (which are usually 1:1 anyway) - While these products are hugely convenient and strong enough for general woodworking, I am very suspicious of these products for boatbuilding - I know of two big boat projects that were glued with these products (against advice) that found in one that you could break bonds with your hands later and another one that had leaks and reliability problems. It is always hard to work out whether it was the builder (what other advice did they not listen to?) or the product.

I hope this gives some quick ways to work out a list of suitable epoxies.

Best wishes
Michael

Hello all,

Originally Posted by Boatmik

1/ It needs to be a "high-solids" type - this means no solvents have been added. If solvents have been added then the epoxy will not prevent the water from getting into the timber. If solvents have been added you can often smell them. Epoxy shouldn't "take your breath away" when you smell it - though the hardener might have a slight ammonia smell.

Yes and true. Nowadays, there is a nice diversity of reactive viscosity cutters providing excellent surface wettability, too, so for woodworking applications there is no real need either to water down epoxies with some passive diluents and solvents.

About curing agents, in some of them the smell part can be pretty pungent by nature, especially with low molecular weight aromatic amines and cycloaliphatic amines. The most stinky curing agents are probably those mercaptan based amines, usually used in fast curing all-purpose adhesives.

But the presence of acetone, xylene etc can be recognized there, at least if you have some previous experience on how they smell like.

2/ Ratios - at this stage the chemistry of economical epoxies requires that they not be a 1:1 ratio. 2:1, 3:1 etc are all fine. I know that there is one knock down price "epoxy" sold in the USA that requires only a small amount of hardener - like 1%. That is not epoxy as we know it, Jim

Catalytic curing agents like those ones based on boron trifluoride are added in the resin part usually between 1%...10%. These metal salt based amine catalysts are often a bit tricky to use, too. They are usually pretty sensitive to water vapour and pH. But their reactivity can be factory-adjusted so that curing occurs at RT from a few seconds (very reactive) to a year (very latent). Those latent ones require then sufficient amount of heat to activate them. They are very effective and useful for things like in potting of electronics and in high-performance prepregs, but not that useful at home. Can be quite harmful and toxic, too.

Often polyamide curing agents provide the most care-free mixing ratio. Generally speaking, the higher the value of active hydrogen there is in the curing agent (higher value of AHEW aka HEW aka H-value) the less there is worry on accuracy of precise mixing ratio. But, this is also case sensitive thing when considering a particular curing agent and the worry about the effect of residual monomers in given application. Critical to very critical applications require sufficient preliminary studies anyway.

3/ Price - Epoxy is expensive to make - so it will never be really cheap. If it is really cheap (and is not on special or being used as a price leader - if it is buy the epoxy from the shop but check carefully the prices of everything else!!!!) then it is likely the quality has been compromised. It might be possible to get the price down 10% but a price of 50% less will usually mean that something has been messed with. Not necessarily - but possibly.

The factory price of BPA epoxy resin coming from major epoxy manufacturers (from Dow, Hexion etc.) is at the moment about 4700 AUD per metric tonne. That's the stock price in the world at the moment. Basic curing agents like DETA, TETA, IPDA etc. are not much more expensive, some are even cheaper.

The price of these materials increases (actually multiplies) rapidly while travelling through all those steps including tradehouses, transportation, formulates design, consulting, manufacturing, packaging into small containers and so on. Lotsa small piston syringes and small cans and bottles including fancy leaflets and colourful wrappings. Marketing costs, salaries, taxes, waste management and all kinds of environmental costs a formulator must cover, and the consumer will be paying about 47000 AUD per metric tonne of plain bisphenol A epichlorohydrin and slightly modified curing agent, possibly also blended with low cost reactive (or non-reactive) diluent. It is business with lotsa steps and high volumes of consumables involved. It is also quite OK and necessary thing, because most of the people will never formulate their own adhesives and resin systems.

But if you wanted to do so, the closer you get to the beginning of the food chain, the more the price will reduce. You will also have more pure raw materials in your use.

4/ Premixed/Gelled Epoxy (which are usually 1:1 anyway) - While these products are hugely convenient and strong enough for general woodworking, I am very suspicious of these products for boatbuilding - I know of two big boat projects that were glued with these products (against advice) that found in one that you could break bonds with your hands later and another one that had leaks and reliability problems. It is always hard to work out whether it was the builder (what other advice did they not listen to?) or the product.

Right. This is the part where you need to do quite a bit of studies by yourself where you listen, read and understand the past experiences of others. Especially the advices of manufacturer.

Nominal performance values for a given preformulated epoxy system may apply only when under certain conditions are fulfilled. For example the amount of the water present in the surfaces you are going to adhere. Environment temperature. Open time vs. water vapour contamination of yet liquid epoxy system. Post curing schedules. Elasticity and water resistivity of cured epoxy system. In-water swelling and off-water shrinking of wooden hull and what the epoxy adhesive thinks of it.

Despite the correct stoichiometric mixing ratios for different systems can be so easily calculated, no software provides the synergy conditions for epoxy system during curing, nor at the adhesive-adherent interface. True predictions can be made only and only by experience.

My experience is at the moment that for a general woodworking and for small time mortars and grouts patches, I mix my epoxies myself. Everything has held together, in moist and freezing conditions. But if I made a boat hull made of wood or man-made fibers, I would use certified systems, at least at this point.

My purpose is not to push my attitudes because everybody can go to a store and purchase a readily figured out epoxy systems. They are very good usually, only a bit unnecessarily expensive for a just general purpose epoxy (to my taste, that is) .

If you want to read some really unfiltered attitude pushing, check out this:
http://www.epoxyproducts.com/
I am not affiliated with this enterprise. It is possible his writing can turn out to be kinda irritating to someone. But, his say is good stuff. Some major points covered.

kippis,

sumu

Cheers Sumu,

Great filling in of gaps in your post - thanks for that!

Good that you identified the number of steps in manufacturing and handling as a major part of the costs.

To that I would probably add Quality Control and some amount of meaningful Research. Which is why I always stick with the big names even though I have to pay a bit more.

I've seen comparative data of engineering testing of different epoxies available in OZ. Different manufacturers choose quite different methods to achieve their aims as the test results are quite different between different epoxies.

However ... the three best performing in terms of energy absorbed to fracture were the three most expensive standard resin systems on the market. Curious!

But the guidelines we both give above would go a long way toward working out if the properties of the epoxy have been tampered with to make it cheaper - basically by cutting it down with something less expensive.

Michael Storer

hi there,

thank you for your answers. but still i need somebodys experience with megapoxy resins because i have already started to construct the boat with it. megapoxy H has Cycloaliphatic curing agents in 3:1 ratio, and i think it has to be good for marine enviroment.

zore

Knowing nothing about the stuff except the above replies, I can't offer an answer on its strength. Depending on how much you've bought of course, having it isn't necessarily a problem. You'll always find a use for it if you decide not to use it for high strength joints, even if it's just filleting and coating and there are joints that don't put big demands on the glue such as seat tops and seat supporting frames

Richard

Howdy Zore,

I checked their website - it is high solids. It is 3:1 so there are unlikely to be problems. The company used to be in New Zealand I think (as Rezana) , but now looks like they are manufacturing in Eastern Europe. They are focussed on the industrial markets - like floors and tanks for liquid.

Michael