silvergrahm
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Do you guys worry about igniting solvents while stirring?
Hello,
I'm mixing up some polymers in acetone at home. It's taking quite of energy to get them into solution. I want to put them on the stir plate, or to use
a drill with a paddle, but I'm worried about igniting the fumes. Should I be?
I work in a lab in a minor role, and the chemist there is constantly paranoid about ignition because he states the hotplates aren't explosion proof.
He's got me worried now too.
Thanks
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zed
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You bet your ass we worry about fires and explosions. Most of us don't want to become crispy critters.
Acetone is not too dangerous, if you have it in the proper glassware, sealed, with a cold water condenser to capture the vapor, and return it to
your reaction flask.
Ether and some other solvents, are much more dangerous.
As for using a drill with a paddle. No problem, provide the drill is an air tool. Air tools, in general, are explosion proof.
Hot plates and stir plates, generally aren't explosion proof. Some are, but their new price, approximates that of a good used car.
Oooops! I am assuming you are attempting to dissolve your polymers in hot, or boiling acetone. If so, you shouldn't need much stirring, but you
surely do need to cool and condense the acetone vapor.
Tell us more.
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PHILOU Zrealone
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Shear rate can induce some friction into the polymer....and thus conversion of cinetic energy into heat.
I had it when mixing silicons into ethanol (80/20 weight%).
The solution was very viscous and increased in temperature.
In your case aceton is quite volatile and flamable...thus "friction heat" if very concentrated at polymer (viscous) will vapourise some of it. If you
use a normal driller you can see sparks into the air holes of it and that is bad news if you work with considerable amounts of aceton.
For the rest some polymers display good electric insulation abilities and can induce high electrostatic charges...this happens with oils in some
industrial processes...at one moment you can get a thunderbolt into your system what can cause a fire...here aceton vapours will obviously take fire
under electrostatic discharge.
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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chemrox
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No
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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Perdurabo
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Yes, but with appropriate ventilation, it shouldn't be an issue unless you're doing something odd. After all, there must be countless stir plates in
chem labs worldwide.
I have seen two accidents that are related to this post. Both involved high-quality rotovaps. One was a rather large ether spill - which the chemist
(not me!) decide to allow to evaporate rather than clean up. The vapors/liquid made their way to the benchtop rotovap which was running at the time,
and either the motor or the water bath circuitry sparked a merry blaze.
The second was an acetone spill (I take credit here). We had a rotovap on the benchtop enclosed in a small, vented enclosure to allow us to rotovap
minor nuisance solvents/reagents outside of the hood. The acetone made its way into the enclosure, overwhelmed the ventilation capabilities, and led
to a small fire. Luckily no real damage, and no injuries.
SO it shouldn't be a problem, but use common sense and keep in mind teh potential buildup of vapors
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silvergrahm
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My home lab is pretty low budget. I only have a stir plate, no heated stir plate. I do have an alcohol lamp for aqueous stuff, but, I'm not about to
use that to heat up the acetone. I could try submersing in a water bath I guess. No fume hood, either.
Luckily I'm only using 2-3% solids so I doubt friction will build up on me.
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zed
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Gear up, Bubba! You gotta have better equipment. Especially, safe to operate equipment. Improvisation is good, but don't be the guy that puts
acetone in his blender, and thereby burns the house down.
You need a heated stir-plate.
In the U.S., such acquisitions are quite inexpensive. A while back, I bought TWO working heated stir plates, on EBay for about 60-70 Dollars total,
including shipping.
I cleaned them up a little bit, and tuned them up, and they worked fine.
If you really can't ventilate, work outside. Though is this age of suspicion and mistrust, legal problems may arise, it is better than getting
scorched in a fire.
Oh, yeah. Sounds like you are trying to dissolve some polymers. Acetone is a pretty good solvent, but if you are trying to dissolve a brick sized
piece of polystyrene, it will take quite a while. Grind up your polymers before trying to dissolve them. The greater the surface area exposed to
solvent, the faster the solution will take place.
[Edited on 31-1-2013 by zed]
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silvergrahm
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Thanks zed you've been helpful. Using powdered cellulose polymers ATM, but they clump up.
I'm a little short on cash, but, you're right, it may be time for that piece of standard equipment. I've got a very nice wooden induction spark coil
that maybe I could get ~$100 for to finance the plate.
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GammaFunction
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My Jenway hot plate has an AC motor and solid state current controls (ie, no relay contacts).
Is this enough not to worry? I generally don't heat solvents, but I'm curious.
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