Air-dried cellulosic fibril foams prepared from one-pot Pickering emulsion

Cellulosic foams are considered ideal green alternatives for insulation or as absorbents but often lack mechanical strength. Their preparation involves freeze drying, chemical crosslinking, or other steps decreasing the sustainability and scalability of the process. This study proposes a novel one-pot preparation to fabricate binder-free, mechanically robust, and high-performance cellulosic-based foam at room temperature. Pickering emulsion templating was used for the wet foam preparation by simultaneous mixing of lignin nanoparticles, polyvinyl alcohol, high-consistency microfibrillated cellulose (MFC), and oil phase. Drying these foams at room temperature resulted in strong and insulating dry foams without added surfactants or chemical cross-linking. The foam structure and its properties were tuned by adjusting MFC content (0–30 % wt of total dry weight) and heptane:pentane ratio (1:1, 2:1, 3:1). Foams with low density (0.10–0.16 g cm⁻³), high porosity (>87 %), low thermal conductivity (36–62 mW m^-1K⁻¹), robust mechanical properties (0.17–0.63 MPa compressive stress at 50 % strain), and promising sound absorption performance (average sound absorption coefficient of 0.3 at 1/3 octave frequency bands) were obtained. This research introduces an approach to create scalable and eco-friendly bio-based foams that could substitute currently used fossil foams, such as polyurethane foam, in thermal insulation application.