Good Heat Resistance: For fully aromatic polyimides, the initial decomposition temperature is generally around 500℃. Polyimides synthesized from biphenyl dianhydride and p-phenylenediamine have a thermal decomposition temperature reaching 600℃, making them one of the most thermally stable polymers to date.
Extreme Low Temperature Resistance: They do not become brittle in liquid nitrogen at a thermodynamic temperature of 4 K (-269℃).
Excellent Mechanical Properties: Unfilled tensile strength is above 100 MPa, with pyromellitic polyimide films reaching 250 MPa and biphenyl polyimide films (Upilex) reaching 530 MPa. As an engineering plastic, its elastic modulus is typically 3-4 GPa. Theoretical calculations show that polyimide fibers synthesized from pyromellitic dianhydride and p-phenylenediamine have an elastic modulus of up to 500 GPa, second only to carbon fiber;
Low coefficient of thermal expansion: The coefficient of thermal expansion of polyimide is between 2×10⁻⁵ and 3×10⁻⁵/℃, while biphenyl-type polyimide can reach 10⁻⁶/℃, comparable to that of metals, and some varieties can even reach 10⁻⁷/℃;
Good processing performance: Polyimide can be processed using most polymer methods, including solution casting, suspension coating, and screen printing, as well as melt processing methods such as hot pressing, extrusion, injection molding, and even transfer molding (RTM) of prepolymers with very low melt viscosity;
Excellent dielectric properties. The relative permittivity of ordinary polyimide is around 3.4. Introducing fluorine, large side groups, or dispersing air at the nanoscale in polyimide can reduce the relative permittivity to around 2.5. The dielectric loss is 10⁻³, and the dielectric strength is 100-300 kV/mm. It maintains good insulation properties over a wide temperature and frequency range.
It is non-toxic and can withstand thousands of sterilization cycles. Some polyimides also have excellent biocompatibility.
Other benefits include high radiation resistance, self-extinguishing polymer properties, low smoke generation, and very low outgassing under high vacuum.
