Epoxy

[Richard W]

I have been using infrared heaters to speed up the hardening process when i have been glueing with epoxy (West). My workshop is otherwise to cold in the winter = 10 centigrades. Recently i have heard that the infrared light will weaken the epoxy. Is there any truth in this?
Richard W

[Gresham CA]

Richard,
I am not sure about IR light but I am sure that epoxy is degraded with ultra-violet light. This is a good question.

[bob goeckel]

richard, why not try posting the question to west system directly? try your searchy thing

[ 01-21-2003, 01:33 PM: Message edited by: bob goeckel ]

[Jim H]

I built a little "one-sheet skiff" out of a sheet of A/C fir plywood and coated it with West Sys epoxy. Nothing else was applied after the epoxy. More than 4 years latter, after being left outside and uncovered in all kinds of weather it's still in good shape with only a minor cloudiness to the epoxy. I was told by the techs at Wesy Sys. that this would not affect structural integrity.

West System Epoxy Website (http://www.westsystem.com/)

[Richard W]

Thank you Gresham, Bob and Jim. I will ask West Systems about my problem. Bu I´m a suspicious guy. Always want to hear the "victims" opinions too. Not only the manufacturer´s promises but hard learned experience.

[John Blazy]

Jim,
did you use the 207 special coatings hardener (for coating use, that is not supposed to cloud up) or did you use 205 fast or 206 slow hardener?

Any cloudiness at all would increase brittleness, but depends on how thick. How thick was it applied?

For Richard, I would think that IR used for small initial doses of heat would not hurt at all. Auto paint shops use IR all the time to speed dry their urethanes as well as epoxy primers. What you heard may have been referring to long time IR exposure, although UV is the most damaging. Better than curing problems arising from too cold an atmosphere.

[Jim H]

John, it was the 205 (fast) hardner. It was my first experience with epoxy coating so it really got slathered on. This thing has sat out in the sun, at the bay. Since it was really just a "test" project I abuse it in ways most boats never are, i.e. as a step stool. I am not a small man and this boat has no internal framing. I have not noticed any cracking or crazing of the epoxy and no indications of water penetration. It sits on the grass in the yard. I did notice a problem with the skeg (something added as an after thought) but I had outgassing problems with it because it was stored in the house and then cut bolted and epoxied all in the same day.

[paul oman]

UV will damage all epoxes, generally by yellowing/chalking. A bit of yellowing etc. is mostly a surface issue and not a real problem.

There are low temp epoxies like LTC 38 (low temp cure 38 degrees F)
find at:

www.epoxyproducts.com/marine.html (http://www.epoxyproducts.com/marine.html)
Epoxy cure is a chemical reaction, controlled by heat (like all chem reactions). The reaction doubles or halves every 18 degrees F.

hope this helps

paul oman
progressive epoxy polymers

[Rosebud]

The heat lamps will not hurt the epoxy at all for the short time you are using them to cure the epoxy. The faster the epoxy cures the better it is. There is a lot of strength gained by keeping it warm while it cures.

Longterm exposure to the sun certainly turns bare epoxy to a chalky surface. If this is a clear coating on an exposed surface be careful to protect it with spar varnish or another UV absorbing varnish.

Good Luck

[thechemist]

Originally posted by Richard W:
I have been using infrared heaters to speed up the hardening process when i have been glueing with epoxy (West). My workshop is otherwise to cold in the winter = 10 centigrades. Recently i have heard that the infrared light will weaken the epoxy. Is there any truth in this?
Richard WAssuming you don't overheat the stuff and char it, it will be okay.

Individual infrared photons don't have enough energy to break the molecular bonds of epoxy products. The short-wavelength ultraviolet photons of sunlight have roughly a hundred times the energy of the long-wavelength infrared photons, and just don't break those molecular bonds.

West does have benzyl alcohol in it, and that is a volatile plastticizer. Infrared heat-cure can evaporate it, and the resulting cured resin will be even more brittle than if it had cured normally at twenty-five degrees C.

[JimConlin]

Richard, don't worry about the West System folks. They're both competent and straight.

[Richard W]

As JimConlin said I will not worry. I´m very aware of West SYS being a serious, liable company.Maby I´m overreacting in my suspiciounes but I´ve had som bad experiences with Sikaflex many years ago. Lost a very important customer because I just read the lable on the tube. (didn´t consult the manufacturer). To make a claim here from Finland is, as you understand almost impossible.
Well West SYS: "I´m a believer!"
But only one last qustion: When we talk about using IR-lights for extra warmth. What is a long time? I usually use the slow hardener and I leave it over the night (8-10 hours).
Richard.

[thechemist]

The rates of chemical reactions double every ten centigrade degrees, roughly.

That does not help much without knowing what the surface temperature is. It could reach a hundred degrees C if the heater was close, and there was no wind-chill.

Don't get it hotter that you can place your bare palm against for five seconds without pain and you should be safe.