| Colorless Transparent Polyimide（CPI）has been widely used in the field of aerospace due to its excellent properties.However,space electron radiation often causes different degrees of damage to CPI material on aerospace devices,resulting in its performance to degrade and seriously affect the normal operation of aerospace devices.Therefore,it is of extremely far-reaching research significance and great practical value great significance to develop CPI films with high light transmittance and excellent electron irradiation resistance.Different types of diamine monomers and dianhydride monomers were explored,and a series of CPI films were designed and prepared.After screening,diamine monomers（TFMB and 6FAPB）and dianhydride monomers（6FDA and CBDA）were selected as raw materials.And then,not only binary copolymers of CPI（TFMB-6FDA）film and CPI（6FAPB-6FDA）film,but also ternary copolymers of CPI（TFMB-6FAPB）film and CPI（6FDA-CBDA）film were successfully prepared.By optimizing the experimental conditions,four different kinds of CPI composite films were prepared.And the electron irradiation experiments of CPI composite films with different doses were carried out.The performance changes of the four kinds of CPI composite films before and after irradiation were studied.The main results were as follows:（1）By changing the total solid content of monomers and the content of IL（Ionic Liquid）,the optimal preparation conditions of the binary copolymer CPI（TFMB-6FDA）film were determined as follows:the total solid content of monomers was 12%,and the IL content was5%.Mg F2/CPI（TFMB-6FDA）composite films were prepared by depositing 150 nm Mg F2films on the better CPI（TFMB-6FDA）film.The transmittance of Mg F2/CPI（TFMB-6FDA）composite film was 92.11%at 600 nm,its maximum transmittance was 94.01%in the wavelength range of 200 nm～800 nm,and the tensile strength of the composite film was 81.23MPa.（2）By changing the total solid content of monomers and the content of IL,the optimal preparation conditions of the binary copolymer CPI（6FAPB-6FDA）film were determined as follows:the total solid content of monomers was 11%,and the content of IL was 5%.Mg F2/CPI（6FAPB-6FDA）composite films were prepared by depositing 150 nm Mg F2 films on the better CPI（6FAPB-6FDA）film.The transmittance of Mg F2/CPI（6FAPB-6FDA）composite film was 91.52%at 600 nm,its maximum transmittance was 93.68%in the wavelength range of 200 nm～800 nm,and the tensile strength of the composite film was 88.40 MPa.（3）By changing the total solid content of monomers,the content of IL,and the molar ratio of the two diamine monomers,the optimal preparation conditions of the ternary copolymer CPI（TFMB-6FAPB）film were determined as follows:the total solid content of monomers was10%,the IL content was 5%,and the molar ratio of the two diamine monomers（TFMB and6FAPB）was 6:4.Mg F2/CPI（TFMB-6FAPB）composite films were prepared by depositing 150nm Mg F2 films on the better CPI（TFMB-6FAPB）film.The transmittance of the composite film was 91.71%at 600 nm,its maximum transmittance was 93.80%in the wavelength range of 200nm～800 nm,and the tensile strength of the composite film was 87.75 MPa.（4）By changing the total solid content of monomers,the content of IL,and changing the molar ratio of the two dianhydride monomers,the optimal preparation conditions of the ternary copolymer CPI（6FDA-CBDA）film are determined as follows:the total solid content of monomers was 10%,and the IL content was 4%.The molar ratio of the two dianhydride monomers（6FDA and CBDA）was 8:2.Mg F2/CPI（6FDA-CBDA）composite films were prepared by depositing 150 nm Mg F2 films on the better CPI（6FDA-CBDA）film.The transmittance of the composite film was 92.11%at 600 nm,its maximum transmittance was93.80%in the wavelength range of 200 nm～800 nm,and the tensile strength of the composite film is 96.01 MPa.（5）After different doses of electron irradiation,the optical property,mechanical property and the thermal stability of Mg F2/CPI（TFMB-6FDA）,Mg F2/CPI（6FAPB-6FDA）,Mg F2/CPI（TFMB-6FAPB）and Mg F2/CPI（6FDA-CBDA）were still excellent.After electron irradiation at the maximum dose(40 ke V,5×1015 e/cm2),the transmittance of the four composite films at 600 nm was still higher than 90%,their tensile strength was over 70 MPa,their decomposition temperature was higher than 383℃when the weight loss was 5%.It shows that the four composite films can still maintain excellent properties after electron irradiation,which can meet the application requirements of space optical systems. |
