Flame Retardant, Heat Insulating Cellulose Aerogels from Waste Cotton Fabrics by in Situ Formation of Magnesium Hydroxide Nanoparticles in Cellulose Gel Nanostructures

Cellulose aerogels with low density,
high mechanical strength,
and low thermal conductivity are promising candidates for environmentally
friendly heat insulating materials. The application of cellulose aerogels
as heat insulators in building and domestic appliances, however, is
hampered by their highly flammable characteristics. In this work,
flame retardant cellulose aerogels were fabricated from waste cotton
fabrics by in situ synthesis of magnesium hydroxide nanoparticles
(MH NPs) in cellulose gel nanostructures, followed by freeze-drying.
Our results demonstrated that the three-dimensionally nanoporous cellulose
gel prepared from the NaOH/urea solution could serve as scaffold/template
for the nonagglomerated growth of MH NPs. The prepared hybridized
cellulose aerogels showed excellent flame retardancy, which could
extinguish within 40 s. Meanwhile, the thermal conductivity of the
composite aerogel increased moderately from 0.056 to 0.081 W m–1 k–1 as the specific surface area
decreased slightly from 38.8 to 37.6 cm2 g–1, which indicated that the excellent heat insulating performance
of cellulose aerogel was maintained. Because the concepts of the process
are simple and biomass wastes are sustainable and readily available
at low cost, the present approach is suitable for industrial scale
production and has great potential in the future of green building
materials.