Polystyrene

Polystyrene (PS) is a synthetic aromatic thermoplastic produced by the polymerization of styrene monomer. It is one of the most widely produced plastics globally, valued for its rigidity, optical clarity in pure form, ease of processing, and low cost. It comes in two principal commercial forms — GPPS and HIPS — with distinct structures and performance profiles.

is the base homopolymer: a clear, brittle, glassy material with excellent transparency, good dimensional stability, and relatively high stiffness. Its main weakness is poor impact resistance — it fractures easily under mechanical stress. GPPS is used where clarity and rigidity matter more than toughness:

• food packaging such as disposable cups, lids, and trays;
• optical light diffusers in LED panels;
• CD and DVD jewel cases;
• laboratory consumables such as petri dishes and test tubes;
• and display packaging where product visibility is important.

is produced by dissolving polybutadiene rubber into styrene before polymerization, creating a two-phase microstructure where rubber particles are dispersed throughout the polystyrene matrix. These particles arrest crack propagation under impact, dramatically improving toughness at the cost of optical clarity — HIPS is opaque. It retains good processability and remains inexpensive.

Application include:

• refrigerator interior liners,
• appliance housings,
• consumer electronics casings,
• yogurt and dairy containers,
• toys,
• signage,
• and point- of-sale display units.

Both grades are easily thermoformed and injection molded. Neither offers meaningful resistance to solvents such as acetone or hydrocarbons, which limits their use in certain environments.

Expanded polystyrene foam, known widely as EPS, is a related but distinct product used in thermal insulation and protective packaging, produced by expanding GPPS beads with a blowing agent rather than forming solid parts.