Polyimide - PI

Polyimide is generally infusible, colored (often amber), high-performance polymer. It has predominantly aromatic molecules and high thermal stability.

Semi-fabricated shapes are often supplied by the polymer manufacturer and manufactured by powder sintering or working with more tractable pre-cursors and completing polymerization in final form, albeit some melt-processable grades of resin are also manufactured.

They have excellent high radiation resistance and temperature properties, low creep and high wear resistance, inherently smoke emission and low flammability, and are very expensive.

They have moderately high water absorption and are prone to hydrolysis and attack by concentrated acids and alkalis.

Advantages

Polyimide has excellent heat resistance up to 260 C (500 F), inherent fire-retardance and low smoke emission. other advantages include low creep, good arc resistance, high wear resistance, transparent to microwave and unaffected by radiation.

Disadvantages

Polymide is xpensive and has poor resistance to alkalies and hydrolysis. Other disadvantages include:

  • low impact strength
  • attacked by concentrated acids.

Applications

Polyimide films are used in capacitors, cable insulation, printed circuit boards, bearings, valve seats, piston rings, and in aerospace;.

Other applications include:

  • engine components
  • mechanical parts exposed to radiation
  • parts for aircraft jet engines
  • IC carriers
  • gears
  • bearing cages
  • coatings for electrical components

Polymide films are used  in aerospace applications for example parts for aircraft jet engines. Image Credit: Shutterstock/FedericoRostagno

Polymide films are used  in aerospace applications for example parts for aircraft jet engines. Image Credit: Shutterstock/FedericoRostagno

Typical Properties

Property Value
Density (g/cm3) 1.42
Surface Hardness RM100
Tensile Strength (MPa) 72
Flexural Modulus (GPa) 2.48
Notched Izod (kJ/m) 0.08
Linear Expansion (/°C x 10-5) 4.5
Elongation at Break (%) 8
Strain at Yield (%) 4
Max. Operating Temp. (°C) 260
Water Absorption (%) 0.3
Oxygen Index (%) 53
Flammability UL94 V0
Volume Resistivity (log ohm.cm) 16
Dielectric Strength (MV/m) 22
Dissipation Factor1 kHz 0.0018
Dielectric Constant 1 kHz 3.62
HDT @ 0.45 MPa (°C) 260+
HDT @ 1.80 MPa (°C) 360
Material Drying hrs @ °C NA
Melting Temp. Range (°C) NA
Mould Shrinkage (%) 0.2
Mould Temp. Range (°C) NA

Source : Abstracted from Plascams

For more information on Plascams please visit The Rubber and Plastics Research Association

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