Hemp Cellulose Nanofibrils (CNF)

Hemp CNF are produced by TEMPO-mediated oxidation (2,2,6,6-tetramethylpiperidine-1-oxyl, 0.1 mmol/g fibre, NaClO 5 mmol/g, NaBr 1 mmol/g, pH 10 adjusted with NaOH, 25°C, 2–5h) converting primary hydroxyl groups at C6 position to carboxylate groups (0.8–1.5 mmol/g, monitored by conductimetric titration), followed by mild mechanical disintegration (Ultra-Turrax 15,000 rpm, 10 min; or microfluidiser 1,200 bar, 3–5 passes). Resulting CNF are long flexible nanofibrils (length 500–2,000 nm, diameter 3–15 nm, aspect ratio 50–150) with surface carboxylate density of 0.8–1.5 mmol/g providing strong electrostatic repulsion (zeta potential −55 to −75 mV). CNF gel viscosity at 1 wt% suspension is 1,000–10,000 mPa·s (Brookfield), forming transparent, flexible films with tensile modulus of 8–14 GPa and strength of 150–250 MPa when cast at 0.05–0.1 mm thickness. Applications include oxygen barrier packaging films (OTR 0.5–2.0 cm³/m²/day), medical wound dressings, and aerogels (density 0.002–0.010 g/cm³, thermal conductivity 0.015–0.020 W/m·K) for insulation.