Effect of Impregnation with a Low-Concentration Furfuryl Alcohol Aqueous Solution on Hygroscopic Properties of Chinese Fir and Poplar Wood

Round 1

Reviewer 1 Report

 

The manuscript concerns the furfurylation of polar and Chinese fir at lower concentrations of furfuryl alcohol than usually applied in furfurylation of wood. While the manuscript is interesting, the authors need to consider their analysis of the wood moisture and how to compare it across the various degrees of modification. Moreover, the English language needs a brush-up. I have compiled the following comments to specific locations in the manuscript:

1)       L52: “The development of furfurylated wood originated in Europe…” This is not correct. The first descriptions of furfurylation of wood is from North America in the 1950ies by I.S. Goldstein.

2)       L57-61: “Meanwhile, furfurylated wood with high concentration will make the modified wood darker in color and it does not significantly improve the dimensional stability compared to low concentration [18,19], both of them are not compatible with the light color and high dimensional stability required for interior furniture and 60 wood products[20]. “ Does wood for interior furniture has to be dimensionally stable? The environment is not very variable and wood species with high shrinkage/swelling such as European beech is often used for furniture and floors.

3)       L65-67: “Furthermore, compared with the greater improvement of mechanical properties and resistance to hygroscopic properties of the furfurylated wood with high concentration of FA,…” What is meant by the “resistance to hygroscopic properties”?

4)       L126-127:” Samples conditioned at 20℃ and relative humidity（RH）33%、65%、95% environment through moisture absorption with 12 replicates, respectively[23].” How was the environment controlled? How stable was the temperature, and what was the balance resolution?

5)       L127-128: “The adsorption tests 127 are conducted continuously from lowest to higher RH.” Were the samples dried out first? Please make sure that enough details are given about the protocol, see e.g. https://doi.org/10.1007/s00226-020-01195-0

6)       L129-130: “The equilibrium moisture content (EMC) and anti-swelling efficiency (ASE) were calculated…” Please be aware that the effect of furfurylation on moisture sorption and swelling of the wood cannot be fully evaluated unless correction is made for the mass gain and bulking of the modification, see e.g. https://doi.org/10.1016/j.ibiod.2013.02.004

7)       L152-154: “The Carr–Purcell–Meiboom–Gill (CPMG) pulse sequence was used to calculate the T2 of the samples, and 18,000 echoes with 64 scans were acquired.” What was the spacing of echoes and the measuring temperature? Also, how was the LFNMR data analysed in terms of exponential decay analysis?

8)        L163, eq. 6: Please be aware that the effect of furfurylation on moisture in the wood cannot be correctly evaluated unless correction is made for the mass gain of the modification, see e.g. https://doi.org/10.1016/j.ibiod.2013.02.004

9)       L166, eq. 7: Please be aware that the effect of furfurylation on the swelling of the wood cannot be correctly evaluated unless correction is made for the bulking of the modification, see e.g. https://doi.org/10.1016/j.ibiod.2013.02.004

10)    L182-183: “However, the density of poplar wood is greater than that of fir wood will lead to too small WPG of the poplar…” The mass gain is relative to the dry mass of the wood, so density in itself cannot explain this. However, differences in porosity and permeability of the impregnation solution, which is somewhat correlated with density, could maybe explain this.

11)    L200-202: “As can be seen from Table 1, The EMC of all furfurylated wood tended to decrease as the WPG increased over the entire humidity range.” See comment #8

12)    L204-205: “It indicates that the furfurylation can effectively reduce the hygroscopicity of poplar and Chinese fir,…” See comment #8

13)    L207: “Compared to EMC, ASE improves more significantly…” See comment #9

14)    Fig. 1: The two diagrams contain too many lines. Please separate the cumulative and differential curves in different diagrams in order to improve the readability of the figure.

15)    Fig. 3: It would be highly recommendable to show CLSM-images of the untreated controls for comparison.

16)    Fig. 4: It is really difficult to see the details indicated by the white arrows with the current degree of magnification.

17)    Fig. 5: The 3D plot of the LFNMR results makes it very difficult to compare untreated and furfurylated wood. Please use a normal 2D plot of the results.

18)    Table 3: The peak integral depends on the smoothening of the LFNMR spectra, so I suggest deleting it. The peak proportion is a fine enough descriptor, however, it is given with far too many decimals. The same goes for the moisture content and T2 time.

19)    There is no discussion of how the LFNMR spectrum changes with furfurylation in terms of the proportion of the different water populations. If the proportion of cell wall moisture content is estimated (based on moisture content and peak proportion of cell wall water), is the reduction in cell wall moisture consistent with what is found under hygroscopic conditions? See e.g. https://doi.org/10.1371/journal.pone.0238319

20)    L342-345: “As it can be seen, FA treatment can effectively reduce the MCWA of fir and poplar, the MCWA of Chinese fir and poplar decreased along with the increasing FA concentration, the average reduction of 63%-88% for fir and 22%-63% for poplar wood compared to control wood.” See comment #8

21)    L355-356: “Thus, although the VR decreased with increasing WPG, it was not as significant as the decrease in MCWA.” See comment #9

 

Author Response

Please see the attachment，thank you.

Author Response File: Author Response.docx

Reviewer 2 Report

Dear authors,

Please follow the attached comment.

 

Line 9, Please put the highlighted sentence between the phrasal verb. (Take … into account)

Line 10, Please remove the (will) then it turns to, Not making

Line 78, Material section: please add the type of the soil, height from sea level, as well as dimeter of the trunk.

Line 99, Did you use a specific standard, please mention it, or did you reach these numbers through trial and error?

Line 182, In my opinion, to better understand this issue for the readers, please mention the dry-density of these two species.

Table 1, please specify the names of the species used in table 1.

Table 1, despite the improvement of ASE, why different results were observed in some concentrations, which are highlighted. Please explain more.

Line 260, add more information.

Line 337. Please compare the stated information with other researches if available. 

 

Table 4, please specify the names of the species used in table 4.

Comments for author File: Comments.pdf

Author Response

Please see the attachment, thank you.

Author Response File: Author Response.docx