writer：Wang, J.; Deng, L.; Guo, L.; Lin, B.; Yang, H.*
keywords：polyimide
source：期刊
specific source：Acta Polymerica Sinica, 2018, 49(4), 507-514.
Issue time：2018年

4,4''''-Diaminobiphenyl-2,2''''-disulfonic acid lead (BDSA(Pb)) is synthesized by ion exchange method, and copolymerized with 4,4''''-diaminodiphenyl ether (ODA) and 1,2,4,5-benzenetetracarboxylic anhydride (PMDA) in N-methyl-2-pyrrolidone (NMP). Through thermal imidization and layer-by-layer casting process, a series of membranes of three-layer sandwich-structured lead-ion-containing polyimide composite material PI(Pb) are prepared, aiming to solve the problems of inhomogeneous distribution of lead, phase segregation and poor mechanical properties. These problems are commonly observed in traditional composite materials prepared by physical blending, which has been widely used for fabrication of X-ray and γ-ray shielding organic-inorganic composite materials by physically doping lead or its salts into a large volume of light-weight, easily-processed polymer matrixe. In this novel sandwich structure, the top and bottom layers are two pure polyimide layers obtained by polymerization of 4,4''''-diaminodiphenyl ether with 1,2,4,5-benzenetetracarboxylic anhydride; the middle layer is the lead-ion- containing polyimide. The chemical and physical properties of this novel PI(Pb) composite material are throughly investigated, using nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, elemental analysis, X-ray diffraction, thermal gravimetric analysis, tensile testing experiments and γ-ray radiation etc. First, the thermal stability and mechanical properties of the PI(Pb) composite materials are examined and analyzed. Secondly, 60Co γ-ray radiation experiment is carried out on pure PI and PI(Pb) materials to analyze and compare their radiation resistance performances. Finally, the low-medium energy γ-ray radiation shielding properties of the materials are investigated using multi-channel gamma spectroscopy. Compared with pure polyimide material, this PI(Pb) composite material has much better γ-ray shielding capability under exposure of low-medium energy γ-rays (such as 241Am, 59.5 keV; and 238Pu, 79.9, 176.7 keV), enhanced radiation shielding rate, much higher linear attenuation and much lower half-value thickness, higher superior radiation resistance, excellent thermal stability and good mechanical performance.