Humidity-Dependent Thermal Boundary Conductance Controls Heat Transport of Super-Insulating Nanofibrillar Foams

•Anisotropic cellulose nanofibril foams are super-insulating also at high humidity•Moisture-induced swelling offsets thermal conductivity increase due to water uptake•Thermal boundary conductance decreases 6-fold by increasing inter-fibrillar gap•Thinner fibrils enhance phonon scattering and reduce the Efficient insulation using biobased materials could energy consumption minimize carbon footprint of buildings. Biobased sensitive moisture, there is a need better understand how moisture controls conductivity. Here, we show that anisotropic can be humidity. The relative humidity dependence nanocellulose controlled moisture-induced replacement air with water. separation distance results in reduction exceeds uptake up Humidity-dependent engineering used tailor heat transfer properties nanofibrillar for packaging management Cellulose nanomaterial (CNM)-based aerogels conductivities substantially below value attract significant interest as energy-efficient green However, hygroscopic CNM-based poorly understood, importance remains unexplored. perpendicular aligned nanofibrils ice-templated lower thinner depends strongly on (RH), lowest (14 mW m?1 K?1) attained 35% RH. Molecular simulations reduced moisture-uptake-controlled fibril-fibril increased foam walls. Controlling transport release potential building applications. Insulation frequently buildings packaging, such gas-filled polyurethane or expanded polystyrene (EPS), derived from fossil sources use hazardous precursors.1Jelle B.P. 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Periodic banding colloidal dispersions.Langmuir. 28: 16512-16523Crossref (42) (i.e., 1.6 mmol COO–g?1) interparticle repulsion41Anderson produce structures 1D). High-resolution scanning electron microscopy (HRSEM) charged compact thin, thickness about 200 1E). difference Brunauer-Emmett-Teller (BET) area (15 m2/g) (8.7 m2/g; Figure much >60-fold predicted upon diameters, suggests tightly packed. Nitrogen experiments performed dry conditions contain fraction (3.5%–5%) S6 S7, Table S1) 12 S3C) diameter. (?r) axial (?a) 2A) 5.9 6.4 kg m?3 mode Hot Disk (Figures S4A S4B). hot disk records time-dependent response transient power pulse determines (?r, S4C). ?r calculated 142Lagüela Bison Peron Romagnoni plane source technique.Thermochim. Acta. 600: 45-51Crossref (46) Scholar:?r=?r?CP(Equation 1) CP specific capacity foam, ? foam. “dry” (RH = 0) differential calorimetry (DSC) RH-dependent > 0 estimated rule mixtures S12) taking account 3A) decreased (and decreasing diameter) CNFs, 1,180 753 J kg?1 CNF2.3, respectively S5). crystal macropores, while perpendicularly CNFs.Figure 3Experimental Hybrid GCMC/MD Simulations Moisture Uptake Foam-Wall-Sorption-Induced SwellingShow full caption(A) Experimental content (H2Ow) mass (CNF2.3-S) function RH% K.(B) (continuous line-?) inter-fibril gap (dashed line-?) RH%, (?) RH%.(C–E) (C) Initial arrangement four individually equilibrated before drying. Snapshots bundle (D) after drying when they come close each other, (E) same subjected swelled entered their interstitial sites. chains colored orange, COO? groups green, counterions pink, blue.View Large Image ViewerDownload (PPT) (A) (B) RH%. 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In contrast, entire range (7%–80% RH) all S4E), CNF- polyoxamer-based foams.26Apostolopoulou-Kalkavoura 2C shows reversible 7% 50% RH, reversible29Kulasinski irreversibly affected investiga