WET-LAID MEETS ELECTROSPINNING
Electrospinningis the state-of-the-art technique for the preparation of nanofibernonwovens. Electro- spun fiber nonwovens have found a wide range of applications in important fields such as tissue engi- neering, plant protection, drug release, super-hydrophobic coatings, composites, sensors, hydrogen storage, fuel cells, and filtration.
But the electrospinning process is difficult to control for the reproducible preparation of well-defined nonwovens. This already hampers technical applications in a significant way. On top of these difficul- ties, the electrospinning process is, compared to other polymer processing techniques, slowregarding the processing of masses and surface area.
The inventors discovered that electrospun fibers with an axial ratio of <500 could be suspended in nearly any solvent. From these suspensions, the nanofibers could be processed to 2D and 3D nonwo- vens of electrospun fibers in a well-controlled manner, which opens completely new perspectives for electrospun fibers. For example, it was possible to prepare by use of dispersions of electrospun fibers self-reinforced polyimide nanocomposites and to prepare 3D ultraporous/ultralight polymer sponges.
It has been shown clearly that nanofiber nonwovens can be prepared on filtration substrates by a wet-laid process of stable suspensions of shortcut electrospun fibers.
The resulting nonwovens compare very well in aerosol filtration to non-wovens obtained directly by electrospinning. This finding offers many advantages for the preparation of nanofiber nonwovens by precipitation from suspension:
- The wet-laid process is much faster and less demanding than the electrospinning of nanofiber nonwovens
- The weight area can be controlled very easily by control of the amount of nanofiber suspension
It can be envisioned that complex shaped substrates could be much easier coated by nanofiber suspen- sion than by electrospinning. Furthermore, the preparation of nanofiber nonwovens with additives, nanofibers of different shape, size, and chemistry could be prepared much easier. With many new materials composites will be possible.
Figure 1: Schematic drawing of nonwoven preparation for filtration apllication directly by electrospinning and precipitation of short nanofibers from suspension
Proof of Concept.