Preparation mechanisms and characteristics of nanofiber aerogels derived from various aramid fibers

Abstract

In this study, aerogels were synthesized using various commercially available aramid fiber types (poly(para-phenylene terephthalamide) (PPTA), poly(para-phenylene/3,4-diphenylether-terephthalamide) (DPE/PPTA), and poly(meta-phenylene isophthalamide) (PMID)), and the differences and correlations between their chemical and molecular chain structures were investigated. Furthermore, the formation process and characteristics of the aerogels were assessed based on aerogel manufacturing conditions. Tetrabutylammonium fluoride and KOH were used as fibrillating agents in the aerogel manufacturing process. The gelation temperature and gelation degree of fibril dispersions were measured at the cooling rates of 2.8℃/min and 0.5℃/min. The molecular interactions and the differences in the microstructure and properties of the aerogels were analyzed via X-ray diffraction analysis, field-emission scanning electron microscopy, Brunauer–Emmett–Teller adsorption analysis, compression testing, dynamic viscoelasticity analysis, and spectroscopy. In particular, the differences in the functional groups of the para-aramid fibers; PPTA-S (Sulfonated on the benzene ring of terephthaloyl component), and PPTA-Cl (Chlorinate on the benzene ring of terephthaloyl component) were analyzed to determine the structure and properties of the physical gels by evaluating the gelation mechanism via the intermolecular interaction that causes fibril adhesion and elongation owing to the differences in the molecular weight and nucleophilicity of the functional groups.