Preparation And Properties Of Light-cured Polyimide And Polyetheretherketone Films

Polyimide（PI）and polyether ether ketone（PEEK）are high-performance engineering plastics with high mechanical strength,excellent thermal stability and good solvent resistance,etc.,which have a wide range of applications in the aerospace and automotive industries.Traditional molding manufacturing requires cutting,chipping,drilling and other subtractive manufacturing operations to prepare engineering plastic parts,resulting in greater waste.3D printing is a way of converting digital models into solid structures,using the principle of layered manufacturing to customize the structure of three-dimensional objects,which has the advantages of short production cycle,high molding accuracy,simple operation and less waste.Applying 3D printing to the production of engineering plastics can simplify the processing process and has great advantages for the production of complex parts.Light-cured 3D printing has excellent printing accuracy and can prepare engineering plastic parts with complex structures.This 3D printing technology requires polymers with good photosensitivity that can be triggered by photoinitiators to produce cross-linked structures under UV light irradiation.Most researchers first synthesize polyimide polymers and polyetheretherketone polymers then introduce photocrosslinking groups into the polymers through their side or end groups.The introduction of photosensitive groups directly into the side chains of monomers through molecular design can precisely modulate the photocurable properties of polymers through photoactive monomers,which is of great research significance.Based on the above background,this paper designed and synthesized a novel photosensitive diamine monomer FMADA and a novel photosensitive diphenol monomer FAAMBH from molecular structure design,and further synthesized two series of photocurable polymers,polyimide and polyether ether ketone,respectively,with commercial monomers.The photocrosslinked polyimide and polyether ether ketone films were prepared by UV curing means,and the effects of the structure and content of the prepared novel diamine monomer and diphenol monomer on the relevant properties of photocrosslinked polyimide and polyether ether ketone films were investigated.The details of the study are as follows:（1）A novel photosensitive diamine monomer FMADA with methacrylate side groups was designed and synthesized from the perspective of molecular structure.The diamine monomer FMADA was polymerized with the commercial monomers hexafluorodianhydride（6FDA）and 4,4’-diaminodiphenyl ether（ODA）to obtain a photosensitive polyimide copolymer（PSPI-x）.The polyimide was dissolved and UV-cured to obtain photocrosslinked polyimide films（UV-PSPI-x）,and the effect of the addition of the photosensitive diamine FMADA on the performance of UV-PSPI-x was investigated.When compared with PI-0 films prepared from pure commercial 6FDA-ODA,the mechanical and thermal properties of UV-PSPI-x showed a trend of increasing and then decreasing,with UV-PSPI-5 having the best mechanical properties with tensile strength up to 105 MPa.UV-PSPI-2.5 had the best thermal properties with5%thermal weight loss(T_d5%)of 470.4°C.The photocrosslinked polyimide films prepared in were characterized for optoelectronic applications due to their black color properties.The UV-visible spectra showed that all the photocrosslinked polyimide films were impermeable in the wavelength range of 250-800 nm,with the best transmittance being UV-PSPI-10 and the worst being UV-PSPI-7.5.Characterization of the dielectric constants showed that the dielectric constants of the photocrosslinked polyimide films increased with the increase of the photosensitive diamine monomer content.When compared with uncrosslinked PI-0,the dielectric constant and dielectric loss of UV-PSPI-x increased,demonstrating its potential as a high-temperature film capacitor.（2）Novel photosensitive diphenol monomers FAAMBH with cinnamate side groups were synthesized from the perspective of molecular design.The monomer FAAMBH was copolymerized with commercial monomers 4,4’-difluorobenzophenone and bisphenol AF to obtain a photosensitive polyetheretherketone polymer（UV-PSPEEK-x）.The poly（ether ether ketone）was dissolved and cured by UV light to obtain cross-linked poly（ether ether ether ketone）films（UV-PSPEEK-x）.The effect of the addition of the photosensitive diphenol monomer FAAMBH on the properties of the photocrosslinked films was investigated.The mechanical properties of UV-PSPEEK-x showed a trend of increasing and then decreasing with the addition of diphenol monomer when compared with uncrosslinked PEEK-0 prepared from pure commercial monomers.UV-PSPEEK-7 and UV-PSPEEK-10 showed the best tensile properties up to 68 MPa.The thermal properties of UV-PSPEEK-x were both lower than those of PEEK-0,and the thermal properties of UV-PSPEEK-x were lower than those of PEEK-0 and decreased with the increase of diphenol monomer content.