键合铅离子的聚酰亚胺材料的制备及辐射屏蔽性能研究

Synthesis and Radiation Proof Property of Lead Ion Containing Polyimide Materials

通过离子交换法合成了对氨基苯甲酸铅盐ABA(Pb);以ABA(Pb)和2,2-双[4-(4-氨基苯氧基)苯基]丙烷(BAPP)为二胺单体、2,2-双[4-(3,4-二羧基苯氧基)苯基]丙烷二酐(BPADA)为二酐单体,N-甲基-2-吡咯烷酮(NMP)为溶剂,采用共缩聚两步法,先后合成了主链含铅离子的聚酰胺酸PAA(Pb)和聚酰亚胺PI(Pb).采用傅里叶变换红外(FTIR)光谱、核磁共振(1H-NMR)光谱和元素分析对ABA(Pb)、PAA(Pb)和PI(Pb)进行了结构表征;应用X射线衍射(XRD)、热重分析(TGA)、力学测试和γ能谱法对PI(Pb)的结构、热稳定性、力学性能及辐射屏蔽性能进行了测试.结果表明,与纯PI材料和同等铅含量、物理掺杂的PI-Pb(NO3)2样品相比,制备的PI(Pb)材料对60Co(1.33 Me V)、60Co(1.17Me V)和137Cs(0.662 Me V)的γ射线具有较大的辐射屏蔽率和较小的半值层厚度,其辐射屏蔽性能要明显优于纯PI材料和同等铅含量、物理掺杂的PI-Pb(NO3)2样品.主要原因在于PI(Pb)中铅离子是通过化学键直接键合到聚酰亚胺主链中的,实现了物理掺杂方法不能达到的铅离子均匀分散,使得γ射线与铅元素发生相互作用的几率增大,从而提高了PI(Pb)对γ射线的辐射屏蔽效果.PI(Pb)材料不仅具有良好的热稳定性和较好的力学性能,而且对γ射线的辐射屏蔽性能优良,有望成为一种具有良好应用前景的轻质γ射线辐射屏蔽材料.

The lead p-aminobenzoic acetate （ABA（Pb）） was synthesized via ion exchange method,and then lead-ion-containing polyamide acid （ PAA （Pb） ） and polyimide （ PI （Pb） ） were prepared by a two-step polycondensation approach, starting with ABA （Pb） and 2,2-bis[4-（4-aminophenoxy）phenyl] propane （ B APP ） as the diamine monomers, 2,2-bis [ 4- （ 3,4-dicarlxyphenoxy ） phenyl ] propane dianhydride （ B PADA ） as the dianhydride monomer in N-methyl-2-pyrrolidinone （NMP） solvent. ABA（Pb） ,PAA（Pb） and PI（Pb） are fully characterized by Fourier transform infrared （FTIR） spectroscopy, proton nuclear magnetic resonance spectroscopy （ ＇ H-NMR） and elemental analysis. X-ray diffraction analysis （ XRD）, thermogravimetric analysis （TGA） ,mechanical tests and γ-ray spectrometry are used to respectively investigate the chemical structure, thermal stability, mechanical property and radiation-proof property of PI （Pb） materials. Compared with pure polyimide material （PI） and PI-Pb（ NO3 ）2 material which is prepared by physically mixing with equal amount of lead element,PI（Pb） material possesses the highest radiation shielding rate and lowest half-value thickness toward radioactive 60Co and 137Cs sources. It demonstrates that PI （Pb） material exhibits the best T-ray radiation-proof property. The key reason is that the lead ions are chemically bonded into the polyimide main chain of PI（Pb） ,which can achieve a high dispersion of lead ions distributed in the matrix. As a result, an increased probability of γ-ray interacting with lead atoms helps improve the radiation-proof property of PI（Pb） material. In conclusion, PI （Pb） material not only exhibits a good thermal stability and a good mechanical property,but also has the best T-ray radiation-proof property, and thus becomes a promising light weight T-ray radiation-proof material.