Effects of deep eutectic solvent (DES) treatment were determined for the chemical composition of the sapwood and heartwood of red pine (Pinus densiflora). Two DES systems were made from the mixture of choline chloride (ChCl) and two different hydrogen bond donors (HBDs), namely, lactic acid (LA) and glycerin (GLY), with different molar ratios (1:2, 1:6, and 1:10). The yield of the solid residue after DES treatment decreased with an increase in the HBD concentration and treatment time, indicating that the water-soluble fraction was increased. The amount of solid residue was lower in the DES with LA than in DES with GLY, and higher in sapwood than in heartwood during both DES treatments. There was no substantial change in the lignin content of the samples, each being 24.7 to 29.5 wt.%, based on the mass of the treated product. Similar to the yield of the solid residue, cellulose and hemicellulose content in the treated product decreased with an increase in the HBD concentration and treatment time, and it was higher in sapwood than in heartwood. The cellulose crystallinity exhibited a slight increase with increasing treatment time, but there was no difference among the treatments using different molar ratios and between sapwood and heartwood.

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Herein for the rst time, lignocellulose nano brils (LCNF) were prepared from pine-wood powder using microwave (MW)-assisted deep eutectic solvent (DES) pretreatment coupled with high-pressure homogenization. A DES based on choline chloride and lactic acid was employed, and LCNFs prepared by conventional DES pretreatment at 110°C (LCNF-110) and 130°C (LCNF-130) were used for comparison.Although MW treatment offered a high removal of lignin (70%) and hemicellulose (90%) within a short time (110 s), the morphological observations by scanning and transmission electron microscopies revealed excellent de brillation of the conventionally heat-treated samples. Likewise, LCNF-110 and LCNF-130 exhibited high tensile strengths of 154.6 ± 5.0 and 136.8 ± 1.2 MPa, respectively, whereas that of LCNF-MW was only 75.6 ± 1.4 MPa. Interestingly, LCNF-MW with a lignin content between that of LCNF-110 and LCNF-130 exhibited high thermal stability (T max 309.6°C) and potent antioxidant properties.However, the lignin contents of the LCNFs determined their UV-radiation blocking e ciency, where LCNF-110 > LCNF-MW > LCNF-130. Furthermore, all LCNF lms exhibited good visible-light transparency, exibility, and water contact angles (> 87°), indicating their promising potential for packaging applications.

Herein for the first time, lignocellulose nanofibrils (LCNF) were prepared from pine-wood powder using microwave (MW)-assisted deep eutectic solvent (DES) pretreatment coupled with high-pressure homogenization. A DES based on choline chloride and lactic acid was employed, and LCNFs prepared by conventional DES pretreatment at 110°C (LCNF-110) and 130°C (LCNF-130) were used for comparison. Although MW treatment offered a high removal of lignin (70%) and hemicellulose (90%) within a short time (110 s), the morphological observations by scanning and transmission electron microscopies revealed excellent defibrillation of the conventionally heat-treated samples. Likewise, LCNF-110 and LCNF-130 exhibited high tensile strengths of 154.6 ± 5.0 and 136.8 ± 1.2 MPa, respectively, whereas that of LCNF-MW was only 75.6 ± 1.4 MPa. Interestingly, LCNF-MW with a lignin content between that of LCNF-110 and LCNF-130 exhibited high thermal stability (Tmax 309.6°C) and potent antioxidant properties. However, the lignin contents of the LCNFs determined their UV-radiation blocking efficiency, where LCNF-110 > LCNF-MW > LCNF-130. Furthermore, all LCNF films exhibited good visible-light transparency, flexibility, and water contact angles (> 87°), indicating their promising potential for packaging applications.