At this point, GAiA’s objective was clear: identify a green-chemistry polymer solution that could be processed by electrospinning into stable fibrous mats suitable for future FFP filter development. The work concentrated on PVA and PAA, two water-soluble polymers chosen as precursors for sustainable nonwoven electrospun fabrics. This choice remained fully aligned with the project’s environmental approach, because the polymer system was designed around water-based processing and around the possibility of producing materials that could be stabilised after electrospinning through thermal esterification.
During this reporting period, the researchers refined the polymer formulations developed in the first phase and progressively narrowed the experimental focus to the most promising compositions. The technical work involved the preparation of PVA/PAA solutions in water, the control of polymer ratios, and continuous cross-checking with characterisation activities to understand how each solution behaved before, during and after electrospinning.
A key part of this work was the search for a balance between processability and final material quality. The team evaluated several PVA concentrations, from lower-viscosity solutions to more concentrated formulations, while maintaining the PAA content in relation to the amount of PVA. The aim was to identify a solution capable of producing fibres with controlled dimensions, homogeneous morphology and no typical electrospinning defects, such as beads or irregular fibre structures.
Rheological analysis played an essential role in this selection. By measuring how viscosity changed with polymer concentration, the team could connect the behaviour of the solution with the quality of the fibres produced. The 10% PVA formulation, identified as sample D, emerged as the best compromise: below this threshold, fibre quality improved progressively, while higher PVA concentrations produced solutions that were increasingly difficult to handle and electrospin. Above 10% PVA, viscosity rose sharply, making syringe loading, Taylor cone stability, flow control and production yield more problematic.
The electrospinning process was then validated around this selected formulation. The technical report describes the optimisation of process parameters such as flow rate, applied voltage, needle-to-collector distance and needle gauge. The final conditions for sample D made it possible to obtain a homogeneous and manageable electrospun mat, with good yield and with the possibility of producing both randomly oriented and aligned fibres without visible defects.
This was an important result for the future filter concept. Producing both random and aligned fibre structures opens the possibility of designing layered filtration systems with different mechanical and structural properties. In the reported process, random fibres were produced using a rotating target at lower speed, while aligned fibres were obtained by increasing the rotation speed of the collector. This gave the project a more flexible fabrication route for developing nonwoven materials tailored to FFP applications.
Material characterisation confirmed the validity of the route. The reporting documents describe the use of several techniques, including FT-IR, SEM, TEM and tensile mechanical testing, to evaluate the selected solution and the resulting electrospun materials. The technical report highlights that SEM and TEM observations confirmed the absence of beads and other visible defects, supporting the choice of sample D as the optimal formulation for continuing the project.
The validation of the electrospinning route also included the assessment of thermal esterification. This step is central to the GAiA material strategy because the PVA/PAA fibre network must become stable after fabrication. The reporting documents explain that the PVA/PAA mixture was selected also because, after electrospinning, the nonwoven fabric can be crosslinked by temperature-induced esterification, making it insoluble in water. This was verified both through FT-IR analysis and through direct tests.
By completing this work, GAiA reached its first project milestone. The second reporting document states that the completion of the WP2 deliverables led to the achievement of the first milestone: D2.2, the validated green-chemistry polymer solution; D2.3, the validated electrospinning process and verification tests; and D2.4, the fabrication of electrospun mats suitable for FFP development.
This milestone changed the maturity of the project. GAiA was no longer working only with preliminary materials: it had established a validated, reproducible route for producing the fibrous base of the future antimicrobial filter. At the same time, the project began moving into the next technological layer, with the synthesis and characterisation of bioactive glass particles with antibacterial properties, preparing the ground for their later integration into the electrospun fibres.
The second phase therefore created the bridge between green polymer processing and antimicrobial functionality. It demonstrated that sustainable water-based electrospinning could produce stable, defect-free nonwoven mats and provided the validated platform needed for the following stages of GAiA: the development of antimicrobial bioactive glasses, their incorporation into the fibre network, and the final validation of safer and greener filter materials for future respiratory protection.
The project was also reported as proceeding according to schedule, with no factors suggesting deviations from the original work plan or from the expected results.
