Definition
A rigid thermoplastic resin made by polymerizing styrene. In aviation, polystyrene is most commonly used in expanded or foam form as a lightweight core material in sandwich structures, and as insulation. It is light, easy to shape, and provides good rigidity when bonded between stronger face sheets, but it is attacked by many fuels, solvents, and polyester resins.
Plain English
A light, stiff plastic — often seen as foam — used as a filler or core inside lightweight aircraft panels and parts.
Context Anchor
Seen in aircraft maintenance when identifying plastic parts, foam forms, packing materials, insulation materials, or materials near fuels and solvents.
Derivation
From 'poly-' (Greek polys, meaning 'many') and 'styrene', the chemical building block. The name simply means 'many styrene units joined together' — a long chain of repeating molecules, which is what makes it a plastic.
Why Pilots Care
Polystyrene foam cores are common in light and homebuilt aircraft, but they dissolve when exposed to fuel, many solvents, or polyester resins. Knowing what is inside a structure matters when choosing cleaners, sealants, or repair materials.
Intuition Check
Do not assume polystyrene is just “any foam.” It is a specific plastic, and its chemical compatibility matters.
Example Sentence 1
The wing was built around a shaped polystyrene foam core covered with fiberglass and epoxy resin.
Example Sentence 2
Technicians packed polystyrene beads around the removed altimeter to keep it safe during transport.