Fabrication of Porous poly(vinylidene fluoride) Fiber via Phase Separation with Low-Toxic Diluent During Thermal Drawing Process

In this study, we developed the fabrication process of hundred-meter long porous poly(vinylidene fluoride) (PVDF) fiber via thermal drawing (TD) method. A cylindrical preform composed of poly(vinylidene fluoride-co-hexafluoropropylene) [P(VDF-HFP)] sheath (cladding) and inner PVDF layer with a circular hole is consolidated at 180 °C for 50 minutes. The fabricated preform has an outer diameter of 25 mm and an inner diameter of 8 mm, in which the thickness of PVDF layer is 1 mm. Thermally-induced phase separation (TIPS) is intended to take place during the TD process to make porous fibers. Unlike previous researches on TIPS, in this study, low-toxic triethylene glycol diacetate (TEGDA) is used as diluent to prepare a PVDF solution, which is good for environment and human body when porous fibers are utilized on wearable devices. The PVDF/TEGDA solution is poured into the center hole of the P(VDF-HFP)/PVDF preform, and then, the preform is thermally drawn at three-zone furnace with temperature distribution of 160, 190, and 120 °C from the top. After the TD process, P(VDF-HFP) cladding and TEGDA diluent are removed with acetone and water, respectively, to expose the porous PVDF fiber. The fabricated porous PVDF fiber has a thickness of about 250 μm and a microporous structure of about 10 μm pore size. These porous PVDF fibers are expected to be used in the development of various functional fibers, supercapacitor fibers, and fabrics that absorbs or reflects IR through pore size control.