Oh, since were on the subject ... I found this thread on Boat Design forum. It was posted my a man with a degree in chemistry and has worked on the testing side for many year. It's really long but I think it should answer the question of epoxy
first or just 2000e on bare frp.
... ok, here goes ... I only posted Colin's reply since that was really only what was relevent.
Sorry if I confused topic by being less than precise talking about Interprotect 2000e. The OP mentioned this, I was talking of this.
I must 1st state that in my youth I worked in the labs for International Paint. I have seen the numbers regarding barrier properties. I have seen numbers regarding barrier properties/corrosion/anti-osmosis properties for many epoxies from hot twin feed to solvent free to solvent based etc. And also competitors and weird high tech stuff.
I originally stated that the Interprotect 2000 was better for use, for the average Joe.
My point of, much "anger" is the phrase used regarding barrier properties.
Actually everything is a barrier...some barriers are better than others. Chemically almost nothing is 100% barrier. In normal use this is not a problem. You only need "sufficient" barrier.
Interprotect 2000e is EXCELLENT barrier. At 250microns it will protect steel
almost as good as you can get. Measured rates of water transmission
(it is standard ISO test but is also tested with other methods) are as low as you need. On GRP it will/does work as barrier.
The use of solvent in a coating CAN make a coating bad but that is not a fact. It is no more true than saying 100% solvent free is better barrier coat.
Sorry for using the example of corrosion
but this is a) more understandable for most people b) is a hideously strongly measured and controlled area of technology. Most, almost all, primers on steel has solvent in them. It doesn't stop make oil
rigs rust to bits.
100% solvent free cannot cure 100%. Solvent helps resin systems cure to higher degree. The solvents are chosen to not be negative in final film.
The clever addition of pigments increase barrier properties over pure resins in most normal cases. A prime example is primers for steel eg oil
rigs. The paints are pigmented. Pigmented for a variety of reasons but a major reason is increase in barrier properties.
The reason the use of pure resin is recommended on exposed glass is to minimise the risk of wicking on the glass ie solvent gets trapped on the size used on the glass which MAY then cause osmosis
under the system. The evidence of this risk is mixed...it depends on the glass size and how it was originally well wetted. There are people who do osmosis repairs
with paint on exposed glass and they have had no problems. The added benefit of resin on the exposed glass is also that you can wet it out good as you see any dry patches. The worry with paint over glass is that someone will just roll on gently and not wet out any dry areas. The story is risk minimisation as opposed to large risk.
I stand by my previous comment. Interprotect 2000E is a barrier. (and in lab better than equivalent thickness than West etc.
ps volume solids mean nothing in this subject. If you applied 10 coats of thinned Interprotect 2000E or 5 unthinned the results would not be noticeable (overcoat times, temp dependent). The higher solid products often give you more risk of failure as you get into this whole problem of degree of cure and there are a load of other paint chemistry factors involved, and I am talking about average molecular size and volume of the curing agent etc. It is interesting but complicated to explain. eg polyethylene has almost ifinite molecular size so it is almost impossible to dissolve/move. 100% solid curing agents are small (this is why they are fluid). The smaller the "bits" you have in your system the more problems you can
Actually interprotect is almost 100% solid WHEN it is cured...ie once the solvent evaporate. Unlike most 100%solid epoxies which are loaded with benzyl alcohol in many cases. This benzyl alcohol is not classed as a solvent for the simple reason that its evaporation rate is so slow as to be not much of problem in most cases. However if you put a film in oven
at 200c for a while you would see weight loss due to evaporation. And also weight loss due to sublimantion of low molecular weight amine in uncured film....but of course heating
film promotes cure thus masking this loss. However it does mean that the resin matrix is not as barrier proof as some people like to imagine.
We will leave it here. You are right, the permeability of Interprotect 2000e is not very good. It is a good barrier. I wasnīt proposing use as sealer.
How a product is called is on MSDS is not always relevant. Especially in labelling ie legal
terms. eg a resin when used as a sealer on wood is a sealer. When used as a resin with glass it is what? Still a sealer? And as a glue.
A primer on steel is a barrier surely.
ps I am a graduate chemist is polymer chemistry. I worked 15 years in paint industry labs. Add in the fact they were the biggest epoxy resin buyers in the world, it is perhaps wise to accept my declaration of fact that Interprotect 2000e is a proven barrier. Sometimes the marketing
bs is true.
Donīt get always so angry or distrustful of the big guy supplier. They often deliver the goods. Whether you think you can do better or cheaper is your choice. It does not detract from fact that sometimes the `marketing hype` is true