Radiation effect of vacuum ultraviolet on the performance of polyimide films

AbstractPolyimide (PI) films equipped on the surface of spacecraft are susceptible to ultraviolet damage. Herein, the performance of two kinds of polyimide films i.e. 3,3',4,4'-biphenyl dianhydride-p-phenylenediamine (BPDA-PDA) and pyromellitic dianhydride-4,4'-oxydianiline (PMDA-ODA) under vacuum ultraviolet (VUV, 172 nm) irradiation was studied. The failure behavior of the PI films was studied by tensile tests, thermogravimetry (TGA), thermomechanical analysis (TMA), electric breakdown, UV-visible transmittance and scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to analyze the molecular structure. The results indicated that the tensile strength of BPDA-PDA PI and PMDA-ODA PI films decreased by 10.4% and 7.4% under VUV irradiation, respectively; the breakdown strength and UV-transmittance also deteriorated. Besides, the surface morphology of the PI films showed a large number of microcracks after VUV irradiation, which we ascribe to the breakage of imide rings (C-N-C) and ether bonds (C-O-C) of the PI films. However, the thermal stability (residual weight) of both PI films remained constant compared to the initial level; this can be explained by the combined effect of bond breaking and cross-linking of the polyimide films.Keywords: Polyimide filmVacuum ultravioletProperty evolutionMolecular structureDisclaimerAs a service to authors and researchers we are providing this version of an accepted manuscript (AM). Copyediting, typesetting, and review of the resulting proofs will be undertaken on this manuscript before final publication of the Version of Record (VoR). During production and pre-press, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal relate to these versions also.