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Polystyrene, Acetone, and Safety
Name: Mindy
Status: other
Grade: K-3
Location: MO
Country: N/A
Date: June 2006
Question:
This is a follow up question to the Polystyrene
foam and Acetone inquiry from Marlene K. on 9/22/04 found in the
chemistry archive. The question is in regards to an experiment
where a small amount of acetone is poured over a polystyrene cup.
Is this experiment safe for children to perform? Besides the
obvious risks of the acetone, are there any fumes or chemicals
created in this experiment that could be harmful or toxic? The
research I have found indicates the experiment is safe as long as
basic lab rules are followed. I would appreciate your help and
expert advice on the safety of this experiment. It is one of
students' favorite chemistry experiments and I would hate to stop doing it!
Replies:
I do not know of any special hazards associated with the "melting"
of the polystyrene other than the one you mention about acetone.
Fire and the inhalation of acetone vapor are the major risks in this
experiment.
Vince Calder
Mindy,
Expanded polystyrene (EPS) or polystyrene foam is typically 90-95%
air, with the rest being the polystyrene and trace substances. The
production of EPS typically involves heating beads of polystyrene
that have been impregnated with a little foaming agent (such as
pentane). The heat causes the pentane to become a gas and expand. As
a result, the beads can expand to about 40-50 times their size and
such bubbles are then molded, pressed, and/or polished into shapes.
Thus, the "danger" can come from the polystyrene, the pentane that
may still be trapped in the object, any contaminant in the synthesis
of the polystyrene, and in the acetone. Polystyrene has minimal
toxicity, there is negligible trapped pentane -since most, if not
all, of it will have diffused out of the pockets and be replaced by
air by the time you get the manufactured objects, there may be some
trace amounts or left over solvents in the synthesis of the
polystyrene -but again this is minimal. So really the real worry is
the acetone.
Acetone MSDS is available here:
http://www.bu.edu/es/labsafety/ESMSDSs/MSAcetone.html
As you can see, the main dangers involve irritation of respiratory
track by inhalation, skin irritation (due to defatting of skin),
irritation of eyes (from fumes or splashing).
I would say, with adult supervision, in a well ventilated room, your
students should continue to enjoy the experience.
Greg (Roberto Gregorius)
Mindy,
Acetone is relatively harmless unless it is ingested. It will tend
to dry your skin because it is miscible with water and evaporates
quickly. The fumes, again, are relatively harmless unless you are
in an enclosed space for an extended period of time. Try Googling
"acetone MSDS" and polystyrene MSDS" to find more specific
toxicology data on these two particular compounds. As far as basic
lab rules are concerned, as long as you have good to decent
ventilation, the kids are not around the fumes for more than 10-20
minutes (the better the ventilation, the longer they can be
around--i.e. by an open window or outside are fine) and you do not
let the kids get their hands in the acetone or resulting dissolved
cup solution, then you should be fine.
Matt Voss
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