Polytetrafluoroethylene fiber fabrication from the continuous melt-spinning process and its properties

Polytetrafluoroethylene (PTFE) has high thermal stability and chemical resistance, and hence is gaining great attention in the industrial field of high-performance filters, membranes, and medical applications. However, since PTFE possesses a narrow gap between melting (330 degrees C) and decomposition temperatures (350 degrees C), the melt-spinning process that is required to satisfy industrial needs for mass production has been limited. Here, perfluoro(propyl vinyl ether) (PPVE) was introduced to decrease the melting point of PTFE then fiber fabrication was performed with the melt-spinning process using a single-screw extruder, enabling the PTFE fiber to fabricate continuously. We selected an optimal melt-spinning condition and obtained PTFE fiber from the melt-processable PTFE/PPVE copolymer. The as-spun PTFE fiber showed low mechanical strength (0.90 g/denier or 89.1 MPa of tenacity). A post-thermal drawing process was performed to increase the mechanical strength of the PTFE as-spun. It demonstrated that the thermally drawn PTFE fiber showed higher mechanical strength (1.84 g/denier or 220.0 MPa of tenacity) due to the increased degree of crystallinity. Also, the other trial, thermal stabilization under N-2, suggested as a future modification method to increase mechanical strength further, preventing thermal constriction of the PTFE fiber. The melt-spun and thermally drawn PTFE fibers were knitted and it was confirmed that the fiber has high chemical resistance and similar surface chemistry to conventional PTFE fibers. This study developed a method to enable a melt-processable PTFE fiber fabrication and opens up opportunities for mass production that is crucial in the industrial aspect.