Isolation of cellulose nanocrystals from medium density fiberboards

Cellulose fibers have been successfully isolated from medium density fiberboards (MDFs) by sodium chlorite oxidation-potassium hydroxide (NaClO₂-KOH) leaching process, at 37.6% yield, comparable to the 39.3% and 37.3% cellulose fibers from eucalyptus and eucalyptus with 12% cured urea-formaldehyde (UF) resin, respectively. At the same sulfuric acid hydrolysis conditions (65% H₂SO₄, 60°C and 30min), MDF cellulose nanocrystals (CNCs) were produced at 27.5% yield, similar to 27.4% of CNC yield from eucalyptus with UF resin, but less than 31.2% yield from eucalyptus. MDF CNCs were slightly thicker in lateral dimension (16.8±8.6nm), less crystalline (59% CrI), and surface esterificated (0.045mmol/g sulfate/CNC) than eucalyptus CNCs (11.6±3.9nm, 75% CrI, 0.060mmol/g) and CNCs from eucalyptus with UF resin (14.9±9.1nm, 65% CrI, 0.046mmol/g). All CNCs were free of UF resin and thermal stable. The residual resin in cellulose pulps hydrolyzed completely during the sulfuric acid treatment and contributed to the unique properties of CNCs. Therefore, CNCs derived from MDF are comparable to CNC from wood and promising for expanded applications.