PPA is a semi-crystalline plastic aromatic polyamide. Its long-term working temperature can reach 180 ℃ and short-term temperature resistance can reach 290 ℃. It has the characteristics of high modulus, high strength, high cost performance, low water absorption, dimensional stability and excellent weldability. LCP is an intermediate state polymer between solid crystal and liquid. It has high strength, high modulus, outstanding heat resistance, minimal linear expansion coefficient, electrical insulation, chemical corrosion resistance, weathering resistance and excellent moulding processability. When the continuous service temperature is 200~300 ℃, its electrical performance will not be affected. The intermittent service temperature can reach about 316 ℃. PEI is an amorphous, non-crystalline high-performance polymer, which has high strength, high rigidity, wear resistance and dimensional stability at high temperature.It has excellent mechanical strength, electrical insulation.