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Typical polyimide exhibits extremely good long-term thermal stability with minimal
thermal expansion, Very high tensile and compressive strength, excellent electrical
insulation properties, minimal thermal conductivity, durability and are inherently
resistant to flame combustion and do not usually need to be mixed with flame
retardants. They are not affected by commonly used solvents and oils like
hydrocarbons, esters, ethers, alcohols, weak acids and freons but not
recommended for use in environments that contain alkalis or inorganic acids. Some
polyimides are solvent-soluble and exhibit high optical clarity. The solubility
properties lend them towards spray and low temperature cure applications.
Strengths: Transparent to microwave and unaffected by UV and Gamma
radiations, very high purity, low outgassing in vacuum, high strength over a wide
temperature range, outstanding load bearing and wear properties, good electrical
properties, excellent repeated sterilization resistance.
Limitations: Very high cost, requires high processing temperatures, post
annealing needed if operating temperatures above Tg, attacked by concentrated
acids and alkalis.
Applications: bushings, bearings, sockets or constructive parts in demanding
applications, test holders, hard disk drive components, electrical connectors, Coil
bobbins, insulating film on magnet wire, flexible cables in electronics, medical
tubing, as insulating and passivation layer in the manufacture of digital
semiconductor and microelectromechanical systems (MEMS) chips, as high-
temperature adhesive in semiconductor industry, used as mechanical stress buffer
and photoresist, polyimide fibres are used in hot gas filtration in coal-fired power
plants, waste incinerators or cement plants.
47) PolyAmide-Imide (PAI):
Is a high performance amorphous engineering thermoplastic, a reaction product of
trimellitic anhydride and aromatic diamines. As the name suggests, PAI posses a
positive synergy of properties from both polyamides and polyimides.The amide
groups impart flexibility and elongation, which results in an engineering plastic with
exceptional toughness.
Density 1.42 g/cm 3
Glass Transition Temperature Tg 278°C
Processing temperature 315 - 370°C
PAI resin is hygroscopic and will pick up ambient moisture. Pre drying is required to
avoid brittle parts, foaming, and other moulding problems. Drying at 149°C for 8 hrs.
or 177°C for 4 hrs. using a dessicant equipped dryer recommended.
PAI can be processed using conventional injection moulding, extrusion or
compression moulding, powder grades to manufacture high-temperature
adhesives, composite matrices, fibres, coatings and films.
PAI is a high-strength plastic with the highest strength and stiffness of any
thermoplastic, performing under severe stress conditions at continuous
temperatures up to 275°C. It has outstanding resistance to wear, creep, broad
chemical resistance including strong acids and most organic solvents, extremely
low coefficient of linear thermal expansion, excellent dimensional stability and
Inherent flame resistance. It also has greater compressive strength and higher

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