The polymerisation of styrene produces the transparent thermoplastic polystyrene (PS).
Polystyrene is crystal clear, hard and impact sensitive in the solid, amorphous form.
As foam (e.g. styrofoam) the material is white and opaque. In this state its strength is lower, but the elasticity is higher.
The foam is often used as packaging material, filler or as insulating material for buildings.
Polystyrene shrinks little during production, so it is preferred for fine contours and straight surfaces in accurate fitting components. For food packaging, shower walls or signs PS is commonly used.