(602d) Reversibly Cross-Linked Nonwoven Fibers: Sustainability Meets Melt Blowing

Melt blowing is a 60-year-old polymer processing method for producing nonwoven polymer fibers. It combines polymer melt extrusion with high-velocity hot air jet fiber drawing to produce nonwoven fibers in a single step. Due to its simplicity and high-throughput nature, melt blowing produces more than 10% of the $50 billion global nonwovens market. Semi-crystalline thermoplastic feedstock, such as poly(butylene terephthalate), polyethylene, and polypropylene, dominate the melt blowing industry due to facile melt processability and product thermal/chemical resistance; other amorphous commodity thermoplastics (e.g., styrenics, (meth)acrylates, silicones, etc.) are generally not employed because they lack one or both attributes. Cross-linking nonwoven products could enable more demanding applications, but cross-linking must be implemented after fiber formation. This presentation describes melt blowing linear acrylic polymers containing cross-linkable functional groups, which were subsequently cross-linked via either a cooling-induced Diels-Alder reaction (e.g., furan-maleimide reaction) or a light-induced cycloaddition reaction (e.g., anthracene photodimerization). The resulting fibers possessed nearly 100% gel content and exhibited enhanced thermomechanical properties with higher upper service temperatures (e.g., ∼180 °C for anthracene-dimer cross-linked acrylic fibers) relative to the linear precursors. Due to the dynamic nature of the reversible cross-links at elevated temperatures, these cross-linked fibers can be recycled after use, providing new avenues toward sustainable nonwoven products.