Reducing Environmental Impact: Solvent and PEO Reclamation During Production of Melt-Extruded PCL Nanofibers

An improved subtractive manufacturing process for fabrication of rectangular, high-surface-area poly(ε-caprolactone) (PCL) fibers is presented. PCL fibers were derived from continuous coextruded tapes of poly(ethylene oxide) (PEO)/PCL with 75% reduction in washing time, while still achieving >99 wt % PCL purity with a quantitative yield of PCL fibers. The fabricated PCL fiber mat had a measured surface area of 3.27 ± 0.53 m²/g. A two-stage distillation process was used to recover methanol and water used in composite solvation to remove PEO. Both methanol and water were recovered at ∼100% purity with a fractional recovery of 87 ± 2% and 95 ± 2%, respectively. Solvated PEO was also recovered at a fractional recovery of 94 ± 4% at ∼100% purity. Gel permeation chromatography and thermal analysis revealed no chain scission, thermal degradation, or cross-linking within the recovered PEO, which suggested the possibility of reincorporating recovered PEO to the multilayer coextrusion process for future composite coextrusion. These waste reduction figures represent recovery on the laboratory-scale process with substantial room for improvement in a fully automated, large-scale industrial process. By reducing overall waste generation >90%, fibers derived from multilayer coextrusion may become an industrially viable alternative for nanofiber manufacturing.