Direct fluorination of para-aramid fibers 1: Fluorination reaction process of PPTA fiber

Abstract

Abstract Fluorination reaction process of PPTA fiber is studied in detail by means of X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) spectra. We prove that the reaction of F 2 with the amide groups is easier than that with benzene rings at the low partial pressure of F 2 (F p ≤10 kPa) due to higher charge density of N atom. With the further increase of F p , the increase of reaction degree of F 2 with the amide group gradually decreases, which may be due to the decrease of the concentration of amide groups. On the contrary, the reaction of F 2 with benzene rings gradually becomes more favorable when F p is higher than 10 kPa resulting from the saving high concentration of benzene rings. The results of FTIR prove that the reaction of F 2 with benzene rings is mainly an addition reaction, rather than a substitution reaction. As the value of F p is lower than 10 kPa, fiber surface morphology is smooth with few grooves. However, more and more lengthwise furrows and grooves are observed on the surface of fluorinated fiber with the further increase of F p . Moreover, the mechanical properties of fluorinated PPTA fibers almost keep constant at the low F p (F p ≤10 kPa). However, when the F p is higher than 10 kPa, the tensile strength of fluorinated PPTA fibers gradually decreases while the initial modulus and crystallinity have a little change.