In a context of ecological transition, aeronautics is moving towards the development of hydrogen-powered aircraft for which lightweight, long-lasting and tough storage tanks must be developed. Among other properties, the tightness of tanks made of polymer and composite materials is of prime importance. This study thus aims at understanding the permeation phenomena through Poly-Ether-Ketone-Ketone (PEKK), which is one of the thermoplastic polymers considered for tank manufacture. In order to better understand the phenomena governing gas permeability, tests were carried out on different PEKK grades of different T/I ratios and degree of crystallinity. The results show that the crystallinity ratio is not the only factor that governs gas diffusion and solubility, but that permeability also depends on PEKK semi-crystalline microstructure. Even if considering crystallites organization through a tortuosity factor improves permeability predictions, permeability can be better understood using a 3 phases description of PEKK microstructure considering distinct contributions of the rigid and mobile amorphous fractions (RAF and MAF). It appears that the MAF permeation does not depend on PEKK T/I ratio, but that gas diffusion and solubility increase for RAF when increasing T/I ratio, thus counterbalancing the blocking effect of crystallites.

中文翻译：

---

半晶微观结构对聚醚酮酮透气性的影响


在生态转型的背景下，航空业正朝着氢动力飞机的发展方向发展，为此必须开发轻质、耐用且坚固的储罐。除其他性能外，由聚合物和复合材料制成的储罐的密封性至关重要。因此，本研究旨在了解聚醚酮酮 (PEKK) 的渗透现象，聚醚酮酮是用于储罐制造的热塑性聚合物之一。为了更好地了解控制透气性的现象，对不同 T/I 比和结晶度的不同 PEKK 等级进行了测试。结果表明，结晶度并不是控制气体扩散和溶解度的唯一因素，渗透率还取决于 PEKK 半结晶微观结构。即使通过弯曲因子考虑微晶组织可以改善渗透率预测，但考虑到刚性和移动非晶部分（RAF 和 MAF）的不同贡献，使用 PEKK 微观结构的 3 相描述可以更好地理解渗透率。看来 MAF 渗透并不取决于 PEKK T/I 比率，但当 T/I 比率增加时，RAF 的气体扩散和溶解度增加，从而抵消了微晶的阻塞效应。