Leachability and Decay Resistance of Wood Polyesterified with Sorbitol and Citric Acid
Round 1
Reviewer 1 Report
Title: not entirely sufficient.
Could be changed to better reflect the leaching issue ... perhaps something like: Leachability and decay resistance of wood polyesterified with sorbitol and citric acid
Abstract: sufficient
Editorial changes:
Line 21: change to "detectable citric acid levels"
Introduction: well organized and has adequate background information
Editorial changes:
Line 69: change at to a
Line 78: change 4 to four
Line 91: Furfurylation misspelled
Line 101: change in to of
Materials and Methods: well organized and detailed; however, there are a few questions:
Line 114: 3:1 molar ratio of what? citric acid to sorbitol? unclear
Equation 2: x100 needs to be adjusted and shouldn't be under the denominator.
Line 147: reads "analysed for the smaller samples used for ATR-FTIR" - means nothing, please give actual specs
Line 149: reads "five times with wood volume" - unclear and needs to be reworded or explained
Results: well described
Editorial changes:
Change the first 3.4 section (Attenuated total reflectance...) to 3.3 (misnumberd)
Line 404: change see to seen
Line 405: there is no Figure 8d - change to Figure 8b
Discussion: well written; includes and describes references to similar studies
Conclusions: sufficient
Other comments: SCA polyesterification has potential but more research is needed before touting it as an alternative to wood treatments currently in use. Additional studies of leachate prevention would be useful. Promising to see SCA deterring decay fungi. This manuscript provides necessary information on alternative wood treatments to the wood preservation industry.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The article under consideration is quite extensive - 22 pages, of which:
- an adequate introduction in the range of approx. 2 pages
- about 4 pages, which deal in detail with the researched material and the methods used
- 5.5 pages dedicated to the results achieved (including 7 figures and 3 tables)
- about 2.5 pages devoted to the discussion of the achieved results
- about 0.5 pages devoted to "unclear and vague" conclusions and proposals for future research
- 6 pages of cited 83 literary sources, mostly the latest knowledge in the field.
Observations:
- inappropriately formulated goal of the presented study (at the end of the Introduction). It needs to be better aligned with the title of the article
- wrong choice of the ATR-FTIR method, which monitors only chemical changes in the surface layers of wood and is therefore not suitable for assessing quantitative changes in samples of grown wood, resp. the KBr pellet technique should be used as described in literature 67, 68
- revise the conclusions in line with the aim of the study, which I recommend to modify.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
The author of this paper presents the results of a low-cost method to reduce the decay of wood against brown-rot and white-rot fungi through a polyesterification with a mixture of sorbitol and citric acid.
The paper is well structured and the results are adequately stressed.
As a minor question regards the possibility to evaluate e compare the conductivity of reference and test samples.
Author Response
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Author Response File: Author Response.docx
Reviewer 4 Report
The author presents results of an investigation of an interesting and potentially useful wood modification technology. The study plan was well thought out and executed. The paper is well written. The results are clearly stated, analyzed, and compared to the literature. The methods and analysis are sound. I compliment the author on work well done.
I have only a few comments which the author can choose to incorporate in this paper or future work as he wishes.
483 – Regarding microcracking of the cell wall: it seems entirely likely that the stress of the bulking and hyper-swelling could create cell wall cracks, which show themselves as peak 1.5. Disappearance of these cracks at ~20 WPG, would be supportive of this hypothesis. This is consistent with the loss of peak 1.5 at -22C.
510 – I think the additional acid groups would be a strong driver for additional swelling, possibly more than the added OH groups, especially at saturation, also the additional nonfreezing water with SCA treatment. The role of acid groups in swellilng can be probed by titration to determine total acid and also by nonfreezing water vs counterion: COOH has much less water swelling potential then COONa, for instance. A few references in this area that I think will be relevant (I had hardcopies back in the day) are provided below if you are interested.
516 – I think it is rather more likely that the swelling is caused by the attraction of water to the COOH groups inside the wood cell wall, driving additional water into the cell wall and promoting superswelling, rather than the conditions during polymerization.
541 – Another potential hazard of this technology is residual acidity driving cellulose depolymerization over the long term, destroying mechanical integrity of the wood
The apparent contradiction between higher nonfreezing water content and decay resistance might be explained by thinking of water as a lubricant of large scale motion of polymers in the cell wall (doi:https://doi.org/10.3390/f10121084 - the large diffusant in fig 3 is anything larger than water, i.e. fungal degradation agents). If the combination of bulking agent and water still limits polymers in the cell wall from engaging in cooperative motion, then you should get decay resistance.
Laine, J.; Stenius, P. Effect of charge on the fibre and paper properties of bleached industrial kraft pulps. Paperi Ja Puu 1997, 79, 257-266.
Salmen, L. Influence of ionic groups and their counterions on the softening properties of wood materials. JPPS 1995, 21, J310-J315.
Berthold, J.; Rinaudo, M.; Salmen, L. Association of water to polar groups; estimations by an adsorption model for ligno-cellulosic materials. Colloids and Surfaces A 1995. While this was written before freezing bound water was shown be an experimental artifact (https://doi.org/10.1016/j.tca.2012.01.015), it's still useful to see the magnitude of water uptake from OH, COOH, and COONa in wood as it approaches saturation.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
