Polystyrene
A widely used, non-biodegradable thermoplastic polymer.
Polystyrene (PS) is a synthetic polymer derived from the aromatic hydrocarbon styrene. It exists in both solid and foamed forms. General-purpose polystyrene is naturally transparent, hard, and brittle, and it is considered a relatively inexpensive resin by weight. The material is a poor barrier to oxygen and water vapor and has a relatively low melting point. As a thermoplastic, it is in a solid, glassy state at room temperature but flows when heated above its glass transition temperature of about 100 °C, becoming rigid again upon cooling. This behavior, which can be controlled through photocrosslinking, allows it to be extruded, molded, or vacuum-formed into shapes with fine detail. Polystyrene is one of the most widely produced plastics, with annual output in the millions of tonnes. Its uses include protective packaging such as packing peanuts and jewel cases, containers, lids, bottles, trays, tumblers, disposable cutlery, models, and phonograph records as an alternative to vinyl. Under ASTM standards, it is not considered biodegradable and accumulates as litter, particularly in foam form, along shores, waterways, and oceans. The polymer was first discovered in 1839 by Eduard Simon, who distilled an oily substance called styrol from storax resin. He observed it thicken into a jelly, which he mistakenly attributed to oxidation. Later work by John Buddle Blyth and August Wilhelm von Hofmann showed the transformation occurred without oxygen, and in 1866 Marcellin Berthelot correctly identified it as a polymerization process. Commercial production began around 1931 by I. G. Farben in Ludwigshafen, using a reactor that extruded polystyrene pellets. Expanded polystyrene foam was developed by Dow Chemical in 1944, and pre-expanded beads using aliphatic hydrocarbons were patented by BASF in 1949.
- chemical_formula
- (C8H8)n
- glass_transition_temperature
- ≈90 °C (atactic)
- density
- 1.05 g/cm3
- common_forms
- atactic (commercial), syndiotactic (XAREC)
Lore & Background
Polystyrene is a synthetic polymer that can exist in either a solid or foamed state. In its general-purpose solid form, it is clear, hard, and brittle, and it is naturally transparent to visible light, though it can be colored with additives. It is considered a relatively cheap resin by weight and serves as a fairly poor barrier to oxygen and water vapor, with a relatively low melting point. As a thermoplastic, it is solid and glassy at room temperature but begins to flow when heated above approximately 100 °C, its glass transition temperature; it becomes rigid again upon cooling. This behavior allows it to be shaped through extrusion, molding, and vacuum forming, capturing fine details in molds. The material is flammable and releases large amounts of black smoke when burned. Under ASTM standards, it is regarded as not biodegradable, and it accumulates as litter in the environment, especially along shores, waterways, and in the oceans, most notably in its foam form. Its properties arise from short-range van der Waals attractions between long hydrocarbon chains, which confer flexibility and elasticity when heated or rapidly deformed. Extruded polystyrene has a density of about 1.05 g/cm³, making it much less dense than aluminum, while offering comparable strength.
Reader's Guide
Polystyrene is significant as one of the most widely used plastics globally, valued for its low cost, transparency, and ease of molding. Its thermoplastic nature allows it to be softened above its glass transition temperature (≈90 °C) and shaped into products ranging from disposable cutlery to insulation foam. However, its non-biodegradability under ASTM standards has led to accumulation as litter, especially in foam form, along shores and in oceans. The material's properties are determined by van der Waals attractions between polymer chains, and its atactic form is the only commercially important type. While generally chemically inert, it dissolves in organic solvents like acetone and burns incompletely. Efforts to recycle it via pyrolysis face high energy costs, and degradation by organisms such as mealworms is very slow.
Did You Know?
- Polystyrene is naturally transparent to visible light but can be colored with colorants.
- Mealworms, the larvae of the darkling beetle Tenebrio, can degrade polystyrene, albeit very slowly.
More in Polymers And Macromolecules 1-24
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record