PEI
Polyetherimide (Ultem)
Glass Transition (Tg)
215–217 °C
Melting Point (Tm)
— (amorphous)
Density
1.27 g/cm³
CAS Number
61128-46-9
Recycling Code
♺ 7
Category
High-Performance
Repeat Unit
–[C₆H₄–O–C₆H₄–C(CH₃)₂–C₆H₄–O–C₆H₄–N(CO)₂]ₙ–
The repeating unit is the smallest structural fragment whose repetition builds the whole chain. Subscripts show the relative share of each unit in copolymers.
Key Properties
Amber transparent amorphous resin; inherently flame retardant with very low smoke; retains stiffness to ~200 °C; sensitive to stress cracking in some solvents.
Applications
Aircraft interior panels, sterilisable medical devices, high-temperature electrical parts.