Acetone, a common organic solvent, interacts dramatically with Styrofoam, the trade name for expanded polystyrene foam. The answer to whether acetone dissolves Styrofoam is a definitive yes, and the process occurs rapidly. This reaction is a physical process, not a chemical change, where the solvent breaks apart the material’s structure. Acetone quickly reduces a large volume of foam into a small, dense residue.
The Structure of Styrofoam
Styrofoam, or expanded polystyrene (EPS), is a plastic created by injecting gas into polystyrene. The base material is polystyrene, a synthetic polymer made of long chains of styrene monomers (hydrocarbons). These long polymer chains form a solid matrix.
During manufacturing, small polystyrene beads are expanded using heat and a blowing agent. This process creates a material consisting of numerous tiny, trapped air pockets. The final foam product is composed of approximately 95 to 98% air, with the remaining small percentage being the solid polystyrene polymer itself.
The Chemical Mechanism of Dissolution
The effect of acetone on polystyrene foam is governed by the principle that “like dissolves like,” based on molecular polarity. Polystyrene is a non-polar, long-chain hydrocarbon. Acetone is an organic solvent with a unique structure, featuring both a polar carbonyl group and non-polar methyl groups. This dual nature allows acetone to interact effectively with both polar and non-polar materials.
The non-polar regions of acetone penetrate the polystyrene structure. Acetone molecules surround and separate the long polymer chains, overcoming the weak intermolecular forces holding the matrix together. This separation is a physical dissolution, not a chemical reaction that breaks covalent bonds. As acetone penetrates the solid polystyrene, it separates the polymer chains, causing the foam structure’s cell walls to collapse. The breakdown releases the trapped air, leading to the visual effect of the foam shrinking.
The Physical Result and Safety Considerations
When Styrofoam is exposed to acetone, the immediate physical outcome is a rapid reduction in volume. The collapse of the polymer structure, caused by the escaping air, makes it look as though the foam has disappeared into a tiny amount of liquid. The final product is not a liquid solution but a highly concentrated, dense, and sticky gel or sludge. This residue is nearly pure polystyrene polymer, which can often be stretched or shaped. The solvent will eventually evaporate from the residue, leaving behind a solidified mass of the original polystyrene material.
Safety precautions are necessary when working with acetone. Acetone is a colorless liquid that evaporates quickly, and its vapors are highly flammable. It must be kept away from any heat source or open flame. The solvent should only be used in a well-ventilated area, such as outdoors or under a fume hood, to prevent the inhalation of concentrated vapors.