Introduction
Experimental
Materials
Pulp pre-treatments
4-Acetamido-TEMPO (4-AT) mediated oxidation
Isolation of the high-lignin content cellulose nanofibrils
Fractionation step | Process | Yield (%) |
---|---|---|
0 | 4-AT mediated oxidation → microfluidized | 97 |
1 | Decantation, sediment (bottom) | 19.1 |
Decantation, upper-phase (top) | 80.9 | |
2 | Centrifugation 1, pellet | 29.9 |
Centrifugation 1, supernatant | 70.1 | |
3 | Centrifugation 2, pellet | 14.9 |
Centrifugation 2, supernatant | 85.1 (48.5% global yield) |
Preparation of nanopaper
Drying under temperature and vacuum (HT)
Drying at normal room conditions under pressure (RT)
Freeze drying of samples (FD)
Fractionation step | Drying technique | Sample code |
---|---|---|
0 (unfractionated) | High temperature (93 °C) and vacuum (95 kPa) | Unfractionated-HT |
Room temperature under pressure | Unfractionated-RT | |
Freeze dried | Unfractionated-FD | |
3 (colloidal stable) | High temperature (93 °C) and vacuum (95 kPa) | Fibrils-HT |
Room temperature under pressure | Fibrils-RT | |
Freeze dried | Fibrils-FD |
Characterization methods
Klason lignin and sugar analysis
Viscosity measurement of microfluidized suspensions
Total charge determination
Morphology of the fibrils and nanopaper
Static contact angle
Thermal properties of nanopaper
Fourier transformed infrared studies
Oxygen barrier properties
Mechanical testing
Results and discussions
Extraction and mechanical pre-treatment
Klason lignin and sugar analysis
Pulp sample | Arabinose (%) | Galactose (%) | Glucose (%) | Mannose (%) | Xylose (%) | Rhamnose (%) | Klason lignin (%) |
---|---|---|---|---|---|---|---|
As received | 0.35 | 1.50 | 59.78 | 0.54 | 6.98 | 0.10 | 28.45 |
Oxidized | 0.12 | 0.96 | 63.82 | 0.35 | 11.73 | 0.05 | 22.95 |
Microfluidization effect on fibril morphology
Fractionation, dimensions and colloidal stability of the LCNF
Total charge determination
Morphology of LCNF and nanopaper
Contact angle
Thermal properties of the LCNF nanopaper
Fourier transformed infrared spectroscopy
Oxygen transmission rate (OTR)
Tensile testing of the nanopaper
Sample | Young’s modulus (GPa) | Ultimate strength (MPa) | Strain to failure (%) |
---|---|---|---|
Unfractionated-HT | 7.61 ± 0.31 | 143.68 ± 5.99 | 3.35 ± 0.43 |
Fibrils-RT | 10.30 ± 0.50 | 184.21 ± 50.20 | 3.87 ± 1.78 |
Fibrils-HT | 11.30 ± 0.55 | 137.78 ± 35.40 | 1.70 ± 0.80 |