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

我们将利用湿润辅助成型和粘合技术，将聚合物的受控熔体吸吸作用应用于多孔氧化性3D支架，用于难熔聚合物的热塑性加工，以及聚合物与金属/陶瓷之间的粘接。初步研究表明，即使是高粘性、难熔聚合物的熔体，如超高相对分子质量的聚四氟乙烯，也会在强大的粘附力的驱动下渗透到这种3D支架中。将一定量的聚四氟乙烯熔融渗透到3D支架中，以完全填充孔隙系统，将产生将PTFE(化学稳定性、低表面能)的优势与3D支架实现的优势(如机械稳定性、形状持久性和即使在高温下也耐刮擦)相结合的混合材料。我们将检查即使是含有中等摩尔质量的聚四氟乙烯的杂化材料是否也表现出这种有利的性能组合。作为应用案例，我们将以可控多孔玻璃为支架，通过润湿辅助成型实现超高、中分子聚四氟乙烯涂层。作为第二个应用案例，3D支架将被用作粘合介质层，将PTFE和弹性体粘合到陶瓷和金属上。为了充分利用3D支架进行聚合物的润湿辅助成型和粘合，需要提高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，我们将阐明合作渗流现象(渗吸前沿加宽、粘性指进、类雪崩渗吸前沿松弛)以及单孔效应(滑移、吸附、毛细上升、前驱膜形成、前驱膜不稳定性)如何影响渗吸。为了达到这些目标，我们将开发空间分辨率极限为50 nm的高分辨率X射线显微镜(HR-XRM)，作为一种非破坏性的3D成像工具，用于监测吸胀。HR-XRM克服了破坏性最先进的3D成像方法的局限性，例如FIB断层扫描。将开发HR-XRM例程，用于研究纳米级特征尺寸的杂交物，成像渗吸前沿，以及绘制3D支架中局部填充水平的地图。我们将测试HR-XRM吸收对比度是否允许将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分辨率限制。此外，还将建立入渗前后、不同入渗阶段和机械冲击后的HR-XRM关联，以及HR-XRM数据与渗流模型的关联程序。此外，HR-XRM的结果还将通过与光学干涉测量的相关性以及来自互补破坏性3D成像方法(如FIB断层扫描)的结果来验证。该项目将受益于PIS的互补专业知识以及Wehrsphn集团正在建立的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.