Styrofoam, the common name for expanded polystyrene (EPS) foam, is a familiar material used in packaging and insulation. Its lightweight and bulky nature makes it difficult to manage as waste. Dissolving Styrofoam offers a practical method to drastically reduce its volume, benefiting disposal and recycling efforts. The ability to dissolve this plastic hinges on the chemical principle known as “like dissolves like.”
The Chemistry of Polystyrene and Solubility
Styrofoam is polystyrene, a synthetic polymer composed of long chains of styrene monomers. This polymer contains only carbon and hydrogen atoms, making it a non-polar substance. Water, a highly polar molecule, cannot effectively interact with these non-polar chains, which is why the foam is water-insoluble.
The foam’s massive volume comes from its composition, which is roughly 95% air trapped within the solid polystyrene matrix. Dissolution is a physical process where a suitable non-polar solvent penetrates the plastic, causing the polymer chains to separate. This separation releases the trapped air, resulting in the material shrinking into a much smaller, dense sludge.
Effective Solvent Methods
The principle of “like dissolves like” allows specific organic solvents to collapse the polystyrene structure. The most accessible household solvent is acetone, often found in nail polish remover. Acetone molecules disrupt the weak intermolecular forces holding the chains together, allowing the foam to quickly collapse into a viscous liquid.
On an industrial scale, potent aromatic hydrocarbon solvents like toluene and xylene can also dissolve polystyrene. These chemicals are highly effective because they share a similar non-polar nature with the polymer. However, these solvents present greater handling hazards due to their flammability and toxicity.
A natural and less hazardous alternative is d-Limonene, a terpene derived from citrus rinds. This bio-solvent is non-toxic and biodegradable, offering an environmentally conscious method for dissolution. D-Limonene’s non-polar character allows it to dissolve polystyrene effectively, reducing the bulk of the foam to as little as five percent of its original volume.
The mechanism for all these solvents is physical dissolution, not a chemical reaction that breaks polymer bonds. The solvent permeates the plastic, separating the polymer chains. This allows the nearly pure polystyrene to be recovered as a thick, concentrated residue, a process utilized in some recycling efforts for volume reduction and purification.
Safety Considerations and Disposal of Liquid Waste
Working with organic solvents requires strict adherence to safety protocols due to their volatility and flammability. Adequate ventilation is necessary, as solvents like acetone evaporate quickly, leading to the rapid buildup of vapors. Using these chemicals outdoors or in a garage with open doors helps manage inhalation risk.
Personal protective equipment is required to prevent direct contact with the skin and eyes. Chemical-resistant gloves made of materials like nitrile are recommended for handling solvents like acetone, as common latex gloves may be compromised.
The resulting product is a concentrated, viscous sludge of polystyrene dissolved in the solvent. This material is considered chemical waste and must not be poured down a drain or placed in the regular trash. The solvent-saturated residue can contaminate water sources and requires specialized handling according to local hazardous waste guidelines. In some cases, the solvent can be allowed to evaporate completely, leaving behind a solidified, dense plastic mass that may be accepted at local recycling facilities.