Polymethacrylimide (PMI) foam is a cross-linked rigid structure foam material with 100% closed cell structure. Its uniform cross-linked cell wall structure can give it outstanding structural stability and excellent Mechanical properties. The main molecular chain is a chain, and the side chain of the foam contains an imide structure, which can be manufactured by various methods. The foam is the heat-resistant foam with the highest strength and rigidity (180～240℃), which can meet the requirements of medium and high temperature, high pressure curing and prepreg process. It has good compatibility with various types of resins and is suitable for use as a core material in high-performance sandwich structures. It can replace honeycomb structures. It is isotropic and can be easily machined into various complex cross-sectional shapes. It does not contain any Freon and is an environmentally friendly material. At present, PMI foam has been widely used in aerospace, aviation, military industry, ships, automobiles, railway locomotive manufacturing, radar, antennas and other fields. PMI foam also has the following performance characteristics:
1. 100% closed-cell structure and isotropic; PMI foam has good heat resistance, heat distortion temperature is 180～240℃; excellent mechanical properties, high specific strength, high specific modulus, it is in various foams The highest; surface contact, with good compression and creep properties; good compatibility with various resin systems.
2. High temperature autoclave molding (180～230℃, 0.5～0.7MPa), vacuum package heating molding (180～230℃, several Pa), and melt injection molding to realize foam interlayer and prepreg One-time co-curing; free of freon and halogen; good fire resistance, non-toxic and low smoke.
3. Excellent dielectric properties: the dielectric constant is 1.05～1.13, and the loss tangent is (1～18)×10-3. In the frequency range of 2 to 26, its dielectric constant and dielectric loss change very little, showing good broadband stability, making it very suitable for the manufacture of radar and radome.
4. Moist heat corrosion of the panel-honeycomb interface without aluminum honeycomb sandwich structure. PMI foam has the advantages of small specific gravity, high temperature resistance, low dielectric constant and loss, high compressive strength, high specific strength, good fatigue and creep resistance, etc. It can be cured in one step with the prepreg; it also has excellent The secondary processing performance can be heated to form products with different curved shapes. Among the foams of the same density, the strength and stiffness of the PMI foam are the highest among all foams. With its excellent comprehensive performance, it has been widely used in large passenger and transport aircraft, fighter jets, helicopters, high-speed trains, wind turbine blades, satellites and launch vehicles, and sports and medical equipment. When PMI foam is used as the core material, the Scrim method, filament winding method, pressure casting method and other methods can be used to make composite materials.