Effect of Impregnation with a Low-Concentration Furfuryl Alcohol Aqueous Solution on Hygroscopic Properties of Chinese Fir and Poplar Wood
Abstract
:1. Introduction
2. Materials and Methods
2.1. Materials
2.2. Methods
2.2.1. Preparation of Furfurylated Wood
- (1)
- Drying: The specimens were placed in an oven at 103 °C for a 24 h drying process, and then the oven-dries mass and tangential, radical, and longitudinal directions were measured after cooling in a desiccator with an accuracy of 0.0001 g and 0.01 mm, respectively.
- (2)
- Impregnation (full cell process): The specimens were first treated under a negative pressure of 0.06 MPa for 0.5 h, then kept under a pressure of 0.4 MPa for 2 h, and finally treated under a negative pressure of 0.06 MPa for 0.5 h [23]. After the impregnation was completed, the excess impregnation solution on the surface was wiped away. Meanwhile, in order to more uniformly diffuse the furfuryl alcohol, each specimen was wrapped in aluminum foil and kept at 30 °C for 72 h.
- (3)
- Curing and drying: The samples were cured in an oven at 103 °C for 6 h, and then the aluminum foil was removed. The furfurylated wood mass M1 and dimensions were obtained after drying; the drying process was carried out at 50 °C for 12 h, followed by 70 °C for 12 h, and finally 103 °C for 24 h. According to the weight percentage gain, the furfurylated poplar and Chinese fir wood impregnated with 0%, 10%, 20%, and 30% concentrations were labeled as PW0, PW17, PW35, PW51, SW0, SW23, SW45 and SW75, respectively.
2.2.2. Morphology and Microstructure
2.2.3. EMC and Dimensional Stability of Adsorption
2.2.4. Mercury Intrusion Porosimetry (MIP)
2.2.5. LF-NMR Analysis
2.2.6. Cyclic Water Soaking and Dimensional Stability
2.2.7. Statistical Analysis
3. Results and Discussion
3.1. WPG and BC of Furfurylation, Hygroscopicity and Dimensional Stability
3.2. Mercury Intrusion Porosimetry (MIP)
3.3. Characterization of FA Distribution
3.4. LF-NMR
3.5. Cyclic Water Soaking and Dimensional Stability
4. Conclusions
- (1)
- Low concentrations of furfuryl alcohol can better enter the cell walls of the Chinese fir than those of poplar. Compared to an FA concentration of 10%–20%, there were no significant increases in the amount of FA entering the cell walls when the FA concentration was increased to 30% in both the Chinese fir and the poplar. Furthermore, the furfurylation of the poplar cell walls was more suitable than those of the Chinese fir cell walls. The FA resin was almost cured in the secondary walls, cell corners, and compound middle lamellae when furfurylated with the 10% concentration. Once the concentration increased to 30%, the amount of FA cured in the cell lumen of the poplar was greater than that of the Chinese fir.
- (2)
- The poplar’s pointed ends of pit chambers and pit apertures (800–1000 nm) and the Chinese fir’s small pores of pit membranes and pit apertures (1–6 μm) were partially infiltrated and deposited by FA resin at the 10%–30% concentrations and formed new pore sizes in the pore size distribution ranges of 80–600 nm and 15–100 nm, respectively. The amount of FA cured in the tracheids of the Chinese fir latewood and poplar wood rays increased along with increasing FA concentrations. The porosity of the poplar was greater than that of the Chinese fir, and the bulk density was lower in the poplar than the fir before and after modification.
- (3)
- Wood impregnation with a low concentration of FA was able to reduce the EMCR and improve the ASE*, but the dimensional stability of the poplar wood was more significantly improved. Additionally, furfurylation effectively reduced water uptake due to the hydrophobicity properties of the furfuryl alcohol resin. Furthermore, with increases in cyclic water soaking times, furfurylation demonstrated significant effects of MCWAR reduction and ASEWS improvement. The MCWAR of the Chinese fir increased by 17%–19% when treated with FA at various concentration in secondary cyclic water soaking, suggesting the loss and leaching of FA resin during the test. In addition, low-field NMR showed that the effects of modification on bound and free water included reductions in the amount of moisture content, tighter bonds between the bound water and wood, and a freer relationship between the free water and wood. It can therefore be concluded that furfurylation is a feasible method by which to extend furfurylated wood applications when using FA at low concentrations.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Sample | FA wt% | WPG | BC | RH/EMCR | RH/ASE* | ||||
---|---|---|---|---|---|---|---|---|---|
33% | 65% | 95% | 33% | 65% | 95% | ||||
SW0 | - | - | - | 5.91 a | 11.23 a | 25.36 a | - | - | - |
(0.42) | (0.02) | (0.69) | |||||||
SW23 | 10 | 23.69 c | 6.22 b | 4.18 b | 9.25 b | 23.55 b | 33.23 | 28.83 | 31.42 |
(1.25) | (0.98) | (0.11) | (0.12) | (0.52) | |||||
SW45 | 20 | 45.80 b | 9.31 a | 4.43 c | 9.14 c | 21.89 b | 30.91 | 41.77 | 37.61 |
(2.52) | (0.93) | (0.14) | (0.29) | (0.79) | |||||
SW75 | 30 | 75.02 a | 9.85 a | 3.83 d | 8.68 d | 22.36 b | 36.42 | 58.24 | 42.80 |
(3.19) | (1.24) | (0.12) | (0.14) | (0.96) | |||||
PW0 | - | - | - | 5.15 a | 11.04 a | 25.22 a | - | - | - |
(0.04) | (0.37) | (0.92) | |||||||
PW17 | 10 | 17.66 c | 11.70 b | 3.83 b | 8.82 b | 22.73 b | 48.45 | 34.94 | 44.98 |
(1.31) | (0.66) | (0.11) | (0.07) | (1.18) | |||||
PW35 | 20 | 35.96 b | 13.73 a | 3.77 c | 8.63 c | 21.49 c | 42.51 | 40.79 | 36.78 |
(3.96) | (0.67) | (0.07) | (0.29) | (0.65) | |||||
PW51 | 30 | 51.07 a | 14.02 a | 3.79 d | 8.53 d | 22.66 c | 77.57 | 51.29 | 55.82 |
(6.07) | (1.16) | (0.07) | (0.62) | (1.10) |
Sample | PW0 | PW17 | PW35 | PW51 | SW23 | SW45 | SW75 |
---|---|---|---|---|---|---|---|
Total intrusion volume mL/g | 1.41 | 1.19 | 0.85 | 0.72 | 1.74 | 1.25 | 1.11 |
Bulk density g/cm3 | 0.47 | 0.52 | 0.64 | 0.68 | 0.40 | 0.47 | 0.52 |
Porosity % | 66.42 | 61.81 | 54.32 | 49.55 | 69.52 | 58.94 | 58.31 |
Sample | Peak | Fully Water-Saturated (%) | T2 Value (ms) | Peak Proportion (%) |
---|---|---|---|---|
SW0 | 1 | 251.7 | 1.1 | 9.9 |
2 | 12.8 | 3.0 | ||
3 | 109.7 | 86.7 | ||
4 | 821.4 | 0.5 | ||
Sum | 100 | |||
SW75 | 1 | 70.0 | 0.6 | 14.6 |
2 | 6.4 | 0.6 | ||
3 | 219.6 | 67.6 | ||
4 | 1245.9 | 17.2 | ||
Sum | 100 | |||
PW0 | 1 | 169.6 | 2.25 | 12.2 |
2 | 11.1 | 2.0 | ||
3 | 54.8 | 44.7 | ||
4 | 471.4 | 41.0 | ||
Sum | 100 | |||
PW51 | 1 | 79.7 | 0.7 | 15.7 |
2 | 15.7 | 0.8 | ||
3 | 102.3 | 5.2 | ||
4 | 880.5 | 78.3 | ||
Sum | 32,528.3 |
Sample | MCWAR (%) | ASEWS (%) | ||||
---|---|---|---|---|---|---|
1st | 2nd | 3rd | 1st | 2nd | 3rd | |
SW0 | 278.57 a | 276.04 a | 277.40 a | |||
(8.85) | 9.94 | (8.85) | ||||
SW23 | 95.80 b | 114.15 b | 120.88 b | 56.56 | 38.42 | 27.40 |
(9.75) | (11.10) | (9.67) | ||||
SW45 | 60.24 c | 70.35 c | 74.20 c | 70.22 | 47.07 | 41.20 |
(1.86) | 2.69 | (50.89) | ||||
SW75 | 57.19 c | 66.70 c | 62.66 d | 70.90 | 51.16 | 42.88 |
(1.39) | 3.29 | (9.21) | ||||
PW0 | 162.22 a | 161.66 a | 160.64 a | |||
(9.65) | (10.31) | (10.97) | ||||
PW17 | 145.17 b | 145.92 b | 147.68 b | 50.48 | 23.32 | 14.90 |
(2.62) | (3.54) | (2.36) | ||||
PW35 | 115.24 c | 118.18 c | 123.04 c | 63.79 | 35.08 | 21.40 |
(8.68) | (10.49) | (9.07) | ||||
PW51 | 89.80 d | 99.15 d | 102.91 d | 72.36 | 45.37 | 23.47 |
(12.08) | (11.74) | (14.34) |
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Sun, H.; Chang, X.; Fu, C.; Yan, Y.; Dong, C.; Chen, T. Effect of Impregnation with a Low-Concentration Furfuryl Alcohol Aqueous Solution on Hygroscopic Properties of Chinese Fir and Poplar Wood. Forests 2022, 13, 1176. https://doi.org/10.3390/f13081176
Sun H, Chang X, Fu C, Yan Y, Dong C, Chen T. Effect of Impregnation with a Low-Concentration Furfuryl Alcohol Aqueous Solution on Hygroscopic Properties of Chinese Fir and Poplar Wood. Forests. 2022; 13(8):1176. https://doi.org/10.3390/f13081176
Chicago/Turabian StyleSun, He, Xun Chang, Changqing Fu, Yuntian Yan, Chunlei Dong, and Taian Chen. 2022. "Effect of Impregnation with a Low-Concentration Furfuryl Alcohol Aqueous Solution on Hygroscopic Properties of Chinese Fir and Poplar Wood" Forests 13, no. 8: 1176. https://doi.org/10.3390/f13081176