BPDA is a useful compound as a raw material for the manufacture of aromatic polyimides, which are currently attracting attention as heat-resistant resins. The method of manufacturing aromatic polyimide by BPDA can be any one of the following methods: the method of manufacturing by polymerization of BPDA with aromatic diamine, the method of closed-loop imidation of polyamic acid obtained by polymerization of BPDA with aromatic diamine at a low temperature near room temperature.

As a high-performance polymer with heat, solvent, and radiation resistance as well as good mechanical and dielectric properties, biphenyl-type polyimide has a wide range of promising applications in mechanical electronics, aerospace, large motors, turbine bearings, and heat-resistant filter materials. Compared with the polyimide with symmetric structure of 3,3',4,4'-biphenyltetracarboxylic dianhydride (4,4'-BPDA) as monomer, the polyimide with asymmetric structure isomer 2,3,3',4'-biphenyltetracarboxylic dianhydride (3,4'-BPDA) as monomer has higher Tg and lower melt viscosity, which significantly improves the processability during material preparation. Therefore, the use of 3,4'-BPDA instead of 4,4'-BPDA base resin has received increasing attention.

Polyimide films

Polyimide films include two types of polyimide films: homophenyl type polyimide films and biphenyl type polyimide films.

First of all, the preparation method of polyimide film is as follows: polyamide acid solution is cast into film, stretched, and then imidized at high temperature. The film is yellow transparent, relative density 1.39 ~ 1.45, has outstanding high temperature resistance, radiation resistance, chemical corrosion resistance and electrical insulation properties, can be used in 250 ~ 280 ℃ air for a long time. The glass transition temperature is 280℃(Upilex R), 385℃(Kapton) and above 500℃(Upilex S), the tensile strength is 200MPa at 20℃ and more than 100MPa at 200℃, especially suitable for flexible printed circuit board substrate and various electric insulation materials for high temperature resistant motors.

Physical properties: thermosetting polyimide has excellent thermal stability, chemical resistance and mechanical properties, and is usually orange in color. The flexural strength of graphite or glass fiber reinforced polyimide can reach 345 MPa, and the flexural modulus reaches 20 GPa. The temperature range of polyimide covers a wide range, from more than a hundred degrees below zero to two or three hundred degrees.

Chemical properties: Polyimide is chemically stable. Polyimide does not require the addition of flame retardants to prevent combustion. Polyimides in general are resistant to chemical solvents such as hydrocarbons, esters, ethers, alcohols and fluorochlorides. They are also resistant to weak acids but are not recommended for use in strong alkaline and inorganic acid environments. Some polyimides such as CP1 and CORIN XLS are soluble in solvents, a property that helps develop their application for spraying and low temperature crosslinking.

This is the basic introduction to the properties of polyimide films! If you want to know more, please contact HAILI and we will provide you with more solutions.