posted on 2018-07-23, 00:00authored byMuhammad Farooq, Mika H. Sipponen, Ari Seppälä, Monika Österberg
Cellulose nanofiber
(CNF) aerogels offer excellent thermal insulation
properties, but high flammability restricts their application.
In this study, CNF aerogels were prepared by incorporating sodium
bicarbonate (SBC), which effectively improved the fire retardancy
without compromising the thermal conductivity of the aerogels, which
was only 28 mW m–1 K–1. The minimum
burning velocity of flame-retardant aerogels was 0.20 cm s–1 at 40 wt % of SBC, which is significantly lower compared to 5.84
cm s–1 of pure CNF aerogels. At the threshold concentration
of 20 wt % SBC, the flame-retardant aerogel demonstrated flameless
pyrolysis along with enhanced char formation. SBC additionally provides
control over the microporosity and morphology, due to the concentration-dependent
formation of lamellar layers during the preparation of aerogels. Overall,
this work describes an efficient method for preparing flame-retardant
CNF aerogels that could lay the foundation for next-generation bio-based
insulation materials.