Hemp Cellulose Nanocrystals (CNC)

Hemp CNC are produced from bleached hemp bast fibre pulp (alpha-cellulose >92%) by controlled sulphuric acid hydrolysis (64 wt% H₂SO₄, fibre:acid ratio 1:8.75 w/v, 45°C, 45–90 min with mechanical stirring) that selectively degrades amorphous cellulose regions while preserving crystalline domains. Resulting CNC are rod-shaped nanocrystals (length 150–400 nm, diameter 6–20 nm, aspect ratio 15–30, crystallinity 75–85% by XRD) with surface sulphate ester groups (0.2–0.5 mmol/g) providing colloidal stability (zeta potential −30 to −50 mV) in aqueous suspension at pH 3–9. Tensile modulus of individual CNC is 100–160 GPa (molecular dynamics simulation), specific surface area 150–400 m²/g (BET). At 5–10 wt% loading in PVA matrix, hemp CNC increases tensile modulus from 1.5 GPa to 5–12 GPa and tensile strength from 50 MPa to 90–140 MPa via stress transfer and physical crosslinking. Yield from hemp pulp is 25–40% CNC (w/w dry basis); acid recovery by dialysis and freeze-drying adds €15–25/kg processing cost. Reported CBD-hemp CNC suspensions exhibit iridescent liquid crystal behaviour above 3–7 wt% concentration.