@article{522, abstract = {Electrospinning can be used to produce nanofiber mats. One of the often used polymers for electrospinning is polyacrylonitrile (PAN), especially for the production of carbon nanofibers, but also for a diverse number of other applications. For some of these applications—e.g., creation of nano-filters—the dimensional stability of the nanofiber mats is crucial. While relaxation processes—especially dry, wet and washing relaxation—are well-known and often investigated for knitted fabrics, the dimensional stability of nanofiber mats has not yet been investigated. Here we report on the wet relaxation of PAN nanofiber mats, which are dependent on spinning and solution parameters such as: voltage, electrode distance, nanofiber mat thickness, and solid content in the solution. Our results show that wet relaxation has a significant effect on the samples, resulting in a dimensional change that has to be taken into account for nanofiber mats in wet applications. While the first and second soaking in pure water resulted in an increase of the nanofiber mat area up to approximately 5%, the dried sample, after the second soaking, conversely showed an area reduced by a maximum of 5%. For soaking in soap water, small areal decreases between approximately 1–4% were measured.}, author = {Grothe, Timo and Sabantina, Lilia and Klöcker, Michaela and Juhász Junger, Irén and Döpke, Christoph and Ehrmann, Andrea}, journal = {Technologies }, keywords = {electrospinning, filter, wet relaxation, dimensions, polyacrylonitrile (PAN)}, number = {1}, title = {{Wet relaxation of electrospun nanofiber mats}}, doi = {10.3390/technologies7010023}, volume = {7}, year = {2019}, } @article{599, abstract = {Electrospinning is a well-known technology used to create nanofiber mats from diverse polymers and other materials. Due to their large surface-to-volume ratio, such nanofiber mats are often applied as air or water filters. Especially the latter, however, have to be mechanically highly stable, which is challenging for common nanofiber mats. One of the approaches to overcome this problem is gluing them on top of more rigid objects, integrating them in composites, or reinforcing them using other technologies to avoid damage due to the water pressure. Here, we suggest another solution. While direct 3D printing with the fused deposition modeling (FDM) technique on macroscopic textile fabrics has been under examination by several research groups for years, here we report on direct FDM printing on nanofiber mats for the first time. We show that by choosing the proper height of the printing nozzle above the nanofiber mat, printing is possible for raw polyacrylonitrile (PAN) nanofiber mats, as well as for stabilized and even more brittle carbonized material. Under these conditions, the adhesion between both parts of the composite is high enough to prevent the nanofiber mat from being peeled off the 3D printed polymer. Abrasion tests emphasize the significantly increased mechanical properties, while contact angle examinations reveal a hydrophilicity between the original values of the electrospun and the 3D printed materials. }, author = {Kozior, Tomasz and Trabelsi, Marah and Mamun, Al and Sabantina, Lilia and Ehrmann, Andrea}, journal = {Polymers}, keywords = {nanofiber mat, electrospinning, water filter, 3D printing, FDM printing, adhesion, stabilization, carbonization}, number = {10}, publisher = {MDPI}, title = {{ Stabilization of Electrospun Nanofiber Mats Used for Filters by 3D Printing }}, doi = {10.3390/polym11101618}, volume = {11}, year = {2019}, } @article{623, abstract = {Electrospinning is a frequently used method to prepare air and water filters. Electrospun nanofiber mats can have very small pores, allowing for filtering of even the smallest particles or molecules. In addition, their high surface-to-volume ratio allows for the integration of materials which may additionally treat the filtered material through photo-degradation, possess antimicrobial properties, etc., thus enhancing their applicability. However, the fine nanofiber mats are prone to mechanical damage. Possible solutions include reinforcement by embedding them in composites or gluing them onto layers that are more mechanically stable. In a previous study, we showed that it is generally possible to stabilize electrospun nanofiber mats by 3D printing rigid polymer layers onto them. Since this procedure is not technically easy and needs some experience to avoid delamination as well as damaging the nanofiber mat by the hot nozzle, here we report on the reversed technique (i.e., first 3D printing a rigid scaffold and subsequently electrospinning the nanofiber mat on top of it). We show that, although the adhesion between both materials is insufficient in the case of a common rigid printing polymer, nanofiber mats show strong adhesion to 3D printed scaffolds from thermoplastic polyurethane (TPU). This paves the way to a second approach of combining 3D printing and electrospinning in order to prepare mechanically stable filters with a nanofibrous surface.}, author = {Kozior, Tomasz and Mamun, Al and Trabelsi, Marah and Wortmann, Martin and Lilia, Sabantina and Ehrmann, Andrea}, issn = {2073-4360}, journal = {Polymers}, keywords = {electrospinning, 3D printing, FDM printing, nanofiber mat, adhesion, water filter}, number = {12}, title = {{Electrospinning on 3D Printed Polymers for Mechanically Stabilized Filter Composites}}, doi = {10.3390/polym11122034}, volume = {11}, year = {2019}, }