Department of Applied Chemistry, School of Science, Northwestern Polytechnical University , Youyi Road 127, Xi'an 710072, China.
ACS Appl Mater Interfaces. 2013 Oct 23;5(20):10207-20. doi: 10.1021/am402957s. Epub 2013 Oct 1.
A novel space survivable polyimide with a variety of desirable properties such as excellent thermal stability, high optical transparency, good mechanical strength, satisfactory break elongation, and outstanding atomic oxygen (AO) erosion resistance has been prepared by first synthesizing hyperbranched polysiloxane (HBPSi) and second incorporating HBPSi into polyimide (PI) chains via copolycondensation reactions. The 29Si nuclear magnetic resonance (29Si NMR) spectrum of HBPSi indicated that HBPSi possessed hyperbranched topology. The ground-based simulated AO exposure experiments demonstrated the mass loss of HBPSi polyimides decreased with increasing HBPSi addition and AO fluence, and it reached as low as 7.7% that of pristine polyimide when HBPSi addition was 29.7 wt % after 22 h AO exposure. Surface morphologies confirmed that pristine polyimide was significantly roughened after AO exposure while HBPSi polyimide had even less rough surface topography. During exposure of HBPSi polyimide to AO, the organic polyimide of the surface was first degraded and a silica protective layer eventually formed, which enabled the surface to be "self-healing". It is this passivation layer that prevents the underlying polymer from additional erosion. The whole preparation process of HBPSi polyimide is moderate, low-cost, environmentally friendly, and suitable for industrialized mass production, which contributes this novel material to a "drop-in" replacement for the widely used Kapton on spacecrafts functioning in space environment.
一种新型的空间可生存性聚酰亚胺，具有多种理想的性能，如优异的热稳定性、高光学透明度、良好的机械强度、令人满意的断裂伸长率和出色的原子氧（AO）抗侵蚀性，已经通过首先合成超支化聚硅氧烷（HBPSi），然后通过共聚缩聚反应将 HBPSi 掺入聚酰亚胺（PI）链中而制备得到。HBPSi 的 29 硅核磁共振（29Si NMR）谱表明 HBPSi 具有超支化拓扑结构。基于地面的模拟 AO 暴露实验表明，随着 HBPSi 加入量和 AO 通量的增加，HBPSi 聚酰亚胺的质量损失减少，当 HBPSi 加入量为 29.7wt%时，经过 22 小时 AO 暴露后，质量损失率低至 7.7%，与原始聚酰亚胺相当。表面形貌证实，原始聚酰亚胺在 AO 暴露后表面明显粗糙化，而 HBPSi 聚酰亚胺的表面形貌甚至更光滑。在 HBPSi 聚酰亚胺暴露于 AO 时，表面的有机聚酰亚胺首先降解，最终形成二氧化硅保护层，使表面能够“自我修复”。正是这种钝化层阻止了底层聚合物的进一步侵蚀。HBPSi 聚酰亚胺的整个制备过程温和、低成本、环保，适合工业化大规模生产，这使得这种新型材料能够“替代”广泛应用于在空间环境中运行的航天器上的 Kapton。
