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Glass and carbon fiber reinforced PEI and other specialty grades are available for
high-strength applications.
Strengths: high HDT 205 °C, Excellent dimensional stability and strength at
elevated temperatures, Transparency to visible, infrared and microwave radiations,
FDA compliant, good repeat sterilization resistance, UV resistance, suitable for
highly demanding applications.
Limitations: pre drying material necessary, very high processing temperature,
Notch Sensitive, attacked by strong bases and partially halogenated solvents,
Relatively high material and processing costs, limited colourability.
Applications: matrix for thermoplastic fiber composites In aerospace, air and fuel
valves, aircraft interiors components, automotive under-hood temperature sensors,
transmission components, thermostat housings, Ignition components, reusable
medical devices, sterilisation trays, dentist devices, pipettes, industrial water-pump
impellers, valves, hot water reservoirs, heat exchange systems, microwavable
bowls, steam pans, food trays.
46) Polyimide (PI):
Typical monomers include pyromellitic dianhydride and 4,4'-oxydianiline.
Depending on the type of interactions between the main chains, polyimides can be
thermoplastic or thermoset resins. Polyimides possess a greater resistance to heat
and fire than any other unfilled organic material and are orange/yellow in colour.
Unlike most plastics, polyimides are available in laminates and shapes, moulded
parts and stock shapes, uncured resins solutions. In general laminates and
mouldings are based on continuous reinforcements where moulding resins contain
chopped (short) fiber reinforcements, made out of thermoset resins although some
are made from thermoplastic grades.
Density 1.31 - 1.43 g/cm 3
Glass transition temperature 250 - 340 °C
Max continuous Service temperature 260 - 360 °C
Polyimide parts are processed by powder-metallurgy methods and conventional
injection, transfer, and compression moulding and extrusion.
Processing temperature: 380 to 430°C
Drying before processing is highly recommended: 5 hours at 200°C.
Even though PI is crystalline polymer, the extruded or injection moulded products
are generally amorphous. In order to improve service temperature (from 240°C in
the amorphous state to 340° in the crystalline state), annealing after processing is
possible.
Injection Moulding: A mould temperature of 170-210°C is recommended.
Extrusion temperature: ~ 400°C, L/D ratio of at least 20-25 is recommended.
Thermosetting polyimides exhibit excellent thermal stability, chemical resistance,
mechanical properties, has very low creep and high tensile strength and these
properties are maintained during continuous use to temperatures of up to 452 °C
and for short excursions, as high as 704 °C. Moulded polyimide parts and laminates
have very good heat resistance and normal operating temperatures exceeds
exceeding 260 °C.

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