Oxidic 3d scaffold structures for wetting-assisted shaping and bonding of polymers

我们将基于控制聚合物的熔体吸胀，开发湿润辅助成型和粘合的多孔氧化3d支架，用于难熔聚合物的热塑性加工，以及聚合物与金属/陶瓷之间的粘合。前期工作表明，在强附着力的驱动下，高粘性、难熔性聚合物（如超高分子质量的聚四氟乙烯）的熔体也能渗透到这种3d支架中。将一定数量的聚四氟乙烯（PTFE）熔体渗透到三维支架中，使其完全填满孔系统，将产生混合材料，结合聚四氟乙烯（PTFE）的优点（化学稳定性，低表面能）和3d支架实现的优点，如机械稳定性，形状持久性和耐划伤性，即使在高温下也是如此。我们将检查含有中等摩尔质量的聚四氟乙烯的杂化是否显示出这种有利的性能组合。作为用例，我们将利用可控多孔玻璃作为支架，通过润湿辅助成型实现超高和中等分子质量PTFE的涂层。作为第二个用例，3d支架将被用作粘合中介层，将聚四氟乙烯和弹性体粘合到陶瓷和金属上。为了充分利用3d支架进行润湿辅助成型和聚合物粘合，需要改进对熔体吸胀作为基本物理过程的预测性理解。为了实现合理的技术渗吸管理，我们将阐明协同渗透现象（渗吸前缘扩大、粘性指动、雪崩状渗吸前缘松弛）以及单孔效应（滑移、吸附、毛细上升、前驱体膜形成、前驱体膜不稳定性）如何影响渗吸。为了实现这些目标，我们将开发空间分辨率限制为50纳米的高分辨率x射线显微镜（HR-XRM），作为监测渗吸的非破坏性3d成像工具。HR-XRM克服了破坏性的最先进的三维成像方法的局限性，如FIB断层扫描。将开发HR-XRM程序，用于研究具有纳米级特征尺寸的杂交种，成像吸吸前沿和三维支架局部填充水平的映射。我们将测试HR-XRM吸收对比是否允许将3d支架的填充部分和空白部分区分为不同类型的有效介质，即使孔隙小于HR-XRM分辨率极限。建立入渗前后、不同入渗阶段、机械冲击后的相关HR-XRM，以及HR-XRM数据与渗流模型的关联例程。此外，HR-XRM结果将通过与光学干涉测量和互补破坏性三维成像方法（如FIB断层扫描）的结果的相关性进行验证。该项目将受益于pi的互补专业知识，以及Wehrspohn集团建立的XRM中心开发的HR-XRM专业知识。

We will exploit wetting-assisted shaping and bonding based on controlled melt imbibition of polymers into porous oxidic 3d scaffolds for thermoplastic processing of intractable polymers as well as for adhesive bonding between polymers and metals/ceramics. As revealed by preliminary works, even melts of highly viscous, intractable polymers such as ultrahigh molecular mass PTFE infiltrate such 3d scaffolds driven by strong adhesion forces. Melt infiltration of an amount of PTFE dimensioned to completely fill the pore system into 3d scaffolds will yield hybrids that combine the advantages of PTFE (chemical stability, low surface energy) with advantages implemented by the 3d scaffold such as mechanical stability, shape persistence and scratch resistance even at elevated temperatures. We will check if even hybrids containing medium molar mass PTFE show this advantageous combination of properties. As use cases we will realize coatings of ultrahigh and medium molecular mass PTFE by wetting-assisted shaping using controlled porous glass as scaffold. As second use case, 3d scaffolds will be exploited as adhesion-mediating layers to bond PTFE and elastomer to ceramics and metals.To fully exploit 3d scaffolds for wetting-assisted shaping and bonding of polymers, predictive understanding of melt imbibition as the fundamental underlying physical process needs to be improved. To enable rational technical imbibition management, we will elucidate how cooperative percolation phenomena (imbibition front broadening, viscous fingering, avalanche-like imbibition front relaxations) as well as single-pore effects (slip, adsorption, capillary rise, precursor film formation, precursor film instabilities) influence imbibition. To meet these objectives, we will develop high-resolution X-ray microscopy (HR-XRM) at the spatial resolution limit of 50 nm as a non-destructive 3d imaging tool for the monitoring of imbibition. HR-XRM overcomes the limitations of destructive state-of-the-art 3d imaging methods such as FIB tomography. HR-XRM routines for studying hybrids with nanoscale feature sizes, for imaging imbibition fronts and for mappings of local filling levels in 3d scaffolds will be developed. We will test whether HR-XRM absorption contrast allows discrimination of filled and empty portions of the 3d scaffolds as different types of effective media even if the pores are smaller than the HR-XRM resolution limit. Moreover, correlative HR-XRM prior to and after infiltration, at different infiltration stages and after mechanical impact will be established, as well as routines for the correlation of HR-XRM data with percolation models. HR-XRM results will moreover be validated by correlation with optical interferometry and results from complementary destructive 3d imaging methods such as FIB tomography. The project will benefit from the complementary expertise of the PIs and from the HR-XRM expertise developed in the XRM center being established in the Wehrspohn group.