Chemical stability of novel melt spinning FEP fibers

Abstract

Fluorinated ethylene propylene (FEP) and polytetrafluoroethylene (PTFE) are both perfluorinated polymer, thus endowing FEP fibers excellent chemical stability. Compared with the difficult processing of PTFE, FEP fibers can be fabricated by melt spinning. The FEP fibers were treated by H2SO4 and NaOH. After treatment, FEP fibers have a slight swelling observed by optical microscope (OM). Meanwhile, the strength of treated FEP fibers decreases slightly, while tensile modulus and elongation at break increases because of the infiltration of H2SO4 and NaOH. Differential scanning calorimeter (DSC) results show that the crystallinity of FEP fibers decreases, due to the regularity of macromolecules destroyed by H2SO4 and NaOH, which enter into crystalline region. This is consistent with WAXD results, indicating crystal size and crystal plane space decreases, owing to the infiltration of H2SO4 and NaOH. However, chemical bonds of FEP fibers are unaffected, which is confirmed by FTIR spectra. Therefore, FEP fibers possess excellent chemical stability.