Polyvinyl alcohol/montmorillonite/magnesium diboride fibers with superior flame retardancy, strength, and flexibility

Using delaminated montmorillonite (MMT) nanosheets (NSs) and MgB2 NSs as crosslinking units and methanol as a coagulation bath, polyvinyl alcohol (PVA)/MMT/MgB2 composite fibers with excellent mechanical and flame-retardant properties were fabricated via wet spinning, and their flame retardancy was studied via limiting oxygen index (LOI) and microcaloric combustion calorimetry measurements. The delaminated MMT NSs (45 wt %) and MgB2 NSs (5 wt%) can be uniformly dispersed into PVA. The synergistic effect between the MgB2 NSs and the MMT NSs as well as the formation of a dense char layer with a continuous crosslinked network significantly enhance the mechanical properties and flame retardancy of the PVA/MMT/MgB2-5 composite fibers. The fibers possess not only a high mechanical strength of 304 MPa and an elongation at break of 9.8% but also an LOI value of 49.8% and a self-extinguishing time of only 1.2 s for a single fiber. Furthermore, the peak heat release rate and the total heat release are 89% and 85% lower than those of the pure PVA fibers, respectively. PVA/MMT/MgB2-5 composite fibers are promising candidates for application in the textile, architecture, and fire protection fields due to their outstanding flame retardancy, high mechanical strength, and good flexibility.