polistiren

Polistiren is a synthetic polymer known in English as polystyrene. It is derived from the monomer styrene, a vinyl benzene compound, and consists of long chains of repeating styrene units. Polystyrene is a thermoplastic, meaning it softens when heated and hardens as it cools, with a glass transition temperature around 95–105 °C. The material is generally transparent when in its general-purpose form but can be modified for different properties.

Production is by addition polymerization of the styrene monomer, using radical initiators. Common polymerization methods include suspension, emulsion, and bulk polymerization. The resulting polymer can be produced in rigid, clear forms or in modified versions that exhibit higher impact resistance.

Polystyrene is produced in several main variants. General-purpose polystyrene (GPPS) is rigid and clear but relatively brittle. High-impact polystyrene (HIPS) blends polystyrene with rubbery components to improve toughness. Expanded polystyrene (EPS) is a foamed version consisting of many air-filled beads used for insulation and lightweight packaging. Extruded polystyrene (XPS) is a closed-cell foam with higher moisture resistance and better thermal performance.

Applications include packaging materials, food service disposables, consumer electronics housings, insulation for buildings and cold storage, and various consumer goods. GPPS is often used for clear food containers and CD/DVD cases, while EPS and XPS are common in insulation and cushioning foams.

Environmental and safety aspects: polystyrene is persistent in the environment and is not readily biodegradable. Recycling exists but rates are variable, and EPS waste can be challenging to collect and process. The styrene monomer is regarded as a hazardous substance, and emissions can occur during processing or incineration if not properly controlled.