Marc Philip Vocht

The proposed restriction of per- and polyfluoroalkyl substances (PFAS) by the European Chemicals Agency (ECHA) covers over 10,000 different substances. The affected materials also include PFAS-related fluoropolymers such as polytetrafluoroethylene (PTFE). Thus, the identification and establishment of substitutes—not only of materials, but also by alternative processing technologies—is not only environmentally desirable, but also an extremely pressing economic issue. This study deals with the potential to process high-temperature polymers into thin-layer-nonwovens. In this context, the meltblow processing of polyethersulfone (PESU) as an amorphous polymer from melt is demonstrated for the first time to the best of the authors’ knowledge. The resulting fabrics were compared with polyetheretherketone (PEEK) as a high-performance reference material owing to its excellent chemical resistance and mechanical properties, as well as to polyphenylene sulfide (PPS), the more widely used industrial standard because of its lower cost, though it exhibits a lower thermal stability, chemical resistance, and mechanical performance than PEEK. Fabrics of 10 g m⁻² were successfully produced with median fiber diameters of 1.39 µm to 2.29 µm. PESU together with PPS achieved the finest median fiber diameters; however, PESU exhibited a lower tensile strength and substantially higher residual elongation than both PEEK and PPS, indicating the need for post-processing by calendering.

Recent research has shown the potential of polyhydroxyalkanoates (PHAs), particularly poly(3–hydroxybutyrate) (P3HB), to form nonwoven structures with fine fiber diameter distributions ranging from 2.5 µm to 20 µm during the meltblow process. The shortcomings of existing fabrics of this type include high brittleness, low elongation at break (max. 3%), and a lack of flexibility. Furthermore, the high melt adhesion and the special crystallization kinetics of PHAs have commonly been regarded as constraints in filament and nonwoven processing so far. However, these two properties have now been used to elaborate a three-dimensional fiber arrangement on a matrix, resulting in the creation of dimensionally and temperature-stable “nonwoven-parts”. Moreover, this study investigated the PHA copolymer poly(3–hydroxybutyrate–co–3–hydroxyhexanoate) (PHBH), revealing a similar processability to P3HB and PHBV in the meltblow process. A significant increase in the (peak load) elongation in the machine direction was observed, reaching values between 5% and 10%, while the tensile strength retained unaltered. The addition of the bio-based plasticizer acetyltributylcitrate (ATBC) to PHBH resulted on an increase in elongation up to 15%. The three-dimensional fabric structure of PHBH exhibited complete resilience to compression, a property that differentiates it from both P3HB and PHBV. However, the addition of the plasticizer to P3HB did not lead to any improvements. This interesting array of properties results in moderate air permeability and hydrophobicity, leading to impermeability to water.

Fiber demand of cellulosic fibers is rapidly increasing; however, these fibers are mainly based on the use of wood pulp (WP), which often have long transport times and, consequently, a high CO₂ footprint. So, alternative pulps based on non-wood, annual fast-growing plants are an option to cover the demand for raw materials and resources. Herein, we report on the use of a novel developed hemp pulp (HP) for man-made cellulosic fiber filament spinning. Commercial WP was used as a reference material. While HP could be used and directly spun as received without any further pretreatment, an additional step to adjust the degree of polymerization (DP) was needed to use the wood pulp. Continuous filaments were spun using a novel dry-jet wet spinning (HighPerCell^® process) technique, which is based on the use of 1-ethyl-3-methylimidazolium octanoate ([C₂C₁im][Oc]) as a solvent. Via this approach, several thousand meters (12,000 m–15,000 m) of continuous multifilament filaments were spun. The HP pulps showed excellent spinning performance. The novel approach allows the preparation of cellulosic fibers for either technical—with high tensile strength—or textile—possessing a low fibrillation tendency—applications. Textile hemp-based filaments were used for first weaving trials, resulting in a flawless fabric.