|
|
keltro@att.net (Kelly Troyer) wrote:
"""
Marv,
It is early and I did not understand the line in quotes ??
"but you can't use it with the towels as wet during application.."
--
Kelly Troyer
Dyke Delta/13B/RD1C/EC2
"""
Hi Kelly,
What I was trying to say was that with epoxy layups you can slop the stuff (MC)all over and you don't need to worry about damaging the surface. Epoxies are pretty tough stuff and the MC, even when applied with towels that are dripping with it, doesn't damage them during the amount of time the chemical is in contact with them. If you've never used the stuff, it flashes off at some very low temperature, so in room temp applications it's gone (evaporated) almost before you're done with it... maybe 15-20 seconds. Polyesters, however, (you know, the stuff they use on boats and shower surrounds... has that "fiberglass" smell that is so familiar if you've ever sanded a speedboat) aren't as resistant to this chemical as are epoxies, so using it in copious quantities on polyester-resin impregnated FRP structures opens the possibility of damaging the structure if you let the MC sit on it too long. Ergo, my statement that you asked about... it suggests that you don't use the paper towels dripping wet with it on those kinds of composites, and implied that lesser quantities of the MC be used when cleaning polyesters. Don't get me wrong, for the amount of contact time the chemical has with the surface when cleaning like this, even a dripping towel won't provide enough MC to start the damage AS LONG AS YOU DON'T LEAVE THE WET TOWEL LAYING ON THE SURFACE after you've done the intial wipe. Leaving the wet towel there, in a ball, allows the MC under the layers of towel to start reacting with the polyester, because you've just turned it into paint stripper with the towel as the agent that helps keep it wet (because it can't evaporate from underneath it) instead of the gel-agent/added-solvents components of Strip-eez. Most of this is common sense stuff... it's just materials dependent.
Here's an analogy for you... I'm an avid shooter/gun collector/home gunsmith. I really love my things that go bang. Several of my old rifles shoot ammo that uses corrosive primers. The chemicals in those primers are so corrosive that, if they are left in the barrel for a matter of hours after a shooting session, they will literally start to eat the inside of the barrel, breech, and breech face. So, anytime I take those rifles and that ammo to the range I also take along a bottle of windex with ammonia and immediately run several patches wetted with it down the barrel and over the other affected parts. Here's where the common sense jumps in. I know that those parts are all steel, and that water (ie, the windex is mostly H2O) will start to rust everything up instantly. So I immediately run dry patches through and then oily patches to protect the surfaces. The guns still look like new, inside and out. If I know that a chemical will damage a surface if left in contact for an extended period, common sense tells me to eliminate that contact as quickly as possible. That's all I'm suggesting here.
I hope that this clears up your questions.
<Marv>
|
|