Highly flame retardant melamine-formaldehyde cross-linked cellulose nanofibrils/sodium montmorillonite aerogels with improved mechanical properties
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A facile cross-linking strategy to construct flame retardant cellulose nanofibril (CNF)/sodium montmorillonite (MMT) aerogels with improved mechanical properties, by incorporating melamine-formaldehyde (MF) resins into precursor suspensions followed by a freeze-drying process, is reported in this work. Scanning electron microscopy images indicate that MF cross-linking does not significantly change the microstructures of CNF and CNF/MMT aerogels. However, the cross-linking improves the materials’ mechanical and flame properties. By incorporating 50 wt% of MF, the compression moduli and compressive stress of CNF aerogels increase by 316% and 114%, respectively. The limiting oxygen index (LOI) value of CNF aerogels also increases from 17.1% to 23.4%. Further addition of MMT increases the CNF aerogels’ LOI value to 57% and increases the maximum decomposition temperature by nearly 20 °C. This occurs because MMT and MF induce a synergistic effect which improves the flame retardant properties of the CNFs aerogels. In CNF/MMT composite aerogels, the introduction of 34 wt% of MF leads to a 54.6% reduction of the peak of heat release rate and a 53.2% decrease in total heat release. CNF aerogels made from sustainable feedstocks with excellent mechanical properties and high flame retardancy, like those discussed herein, show promise as fire resistant biofoams
CitationWang, L., Cui, L., Sanchez-Soto, M., Shou, W., Xia, Z., Liu, Y. Highly flame retardant melamine-formaldehyde cross-linked cellulose nanofibrils/sodium montmorillonite aerogels with improved mechanical properties. "Macromolecular materials and engineering", 2018, vol. 303, núm. 10, p. 1800379.1-9.
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