High performance all-para-aramid paper prepared by impregnating heterocyclic aramid into poly(p-phenylene terephthalamide) microfiber/nanofiber-based paper

All-para-aramid paper with both excellent mechanical properties and thermal stability is of great significance for the manufacture of specialty honeycomb materials. Herein, a facile method is reported for the preparation of high performance all-para-aramid paper by impregnating heterocyclic aramid (HA) solution into a para-aramid paper (PAP) produced with poly(p-phenylene terephthalamide) (PPTA) short fibers and polymerization-induced para-aramid nanofibers (PANFs). Field emission scanning electron microscopy in combination with microscopic Fourier transform infrared spectroscopy were used to confirm successful coating of HA on paper surface and infiltration of HA inside PAP. Since HA molecules in solution have similar structure to PPTA molecules and much stronger ability to form hydrogen bonds than PPTA fibers, they can effectively act as a binder for both types of PPTA fibers, greatly enhancing the interfacial adhesion between fibers and densifying the paper structure. As a result of these structural changes and also of the excellent mechanical properties of HA itself, the HA-impregnated PAPs (HA/PAPs) exhibit much better mechanical properties than neat PAP. The tensile strength of HA/PAP can be up to 128.5 MPa, 4.8 times that of neat PAP. The internal bond strength of HA/PAP can reach 356.1 J/m2, being 4.5 times that of neat PAP, showing dramatically improved delamination resistance. All-para-aramid HA/PAPs possess intrinsically excellent thermal stability and flame retardancy.