Highly efficient flame-retardant and low-smoke-toxicity poly(vinyl alcohol)/alginate/ montmorillonite composite aerogels by two-step crosslinking strategy.

A highly efficient flame-retardant and ultra-low-smoke-toxicity biodegradable material, poly(vinyl alcohol) (PVA)/alginate/montmorillonite (MMT) composite aerogel, was fabricated by a new environment-friendly two-step crosslinking strategy using borate and calcium ions. Compressive and specific moduli of the crosslinked PVA/alginate/MMT (P4A4M4/BA/Ca) aerogel increased to 7.2- and 1.9-folds those of the non-crosslinked aerogel, respectively, and the limited oxygen index value increased to 40.0%. Cone calorimeter tests revealed that the total heat release and peak heat release rate values of the P4A4M4/BA/Ca composite aerogel distinctly decreased. Remarkably, the total smoke release value of the P4A4M4/BA/Ca aerogel was considerably lower than those of non-crosslinked PVA composite aerogels, indicating its superior smoke suppression ability and high fire hazardous safety. The flame-retardancy mechanism of the crosslinked P4A4M4/BA/Ca composite aerogels involved a combination of the gaseous phase and condensed phase flame retardancy. The high-performance PVA/alginate/MMT biodegradable composite aerogels with good sustainability is a promising alternative to conventional flame-retardant foams.