Combination of polyethylene glycol impregnation and paraffin heat treatment to protect round bamboo from cracking

Round bamboo has drawn more and more attention in architecture, decoration and recreational products. Splitting brings some safety problems, which shorten the service life of round bamboo. In this paper, three schemes were adopted as follows to solve the problem: round bamboo was impregnated in polyethylene glycol (PEG)-1000 solution alone, heat treatment in paraffin alone or treated with the combination of PEG impregnation and paraffin heat treatment (PEG–PH). The treated bamboo was exposed outdoors for 26 weeks to evaluate the development of cracks. Results showed as follows: the initial split of PEG–PH-treated bamboo appeared after 22 weeks, while that of the controls after 2 weeks, the total length of cracks was 2271.31 and 873.5 mm for the control and PEG–PH-treated bamboo, respectively. To reveal the reasons for reduced cracks, scanning electron micrograph (SEM) was employed to observe the microstructure of bamboo; besides, hydrophobicity of bamboo was characterized by the water contact angle. PEG can swell the cell wall and the better hydrophobicity of round bamboo could be achieved after PEG–PH treatment. Therefore, the combination of PEG immersion and paraffin heating is an effective and practicable method in bamboo treatment, especially for round bamboo with high moisture content.


Comments to the Author(s)
This paper uses the combination of PEG immersion and paraffin heating to solve the splitting problem for round bamboo. Compared with other existing processes, the method proposed in this paper helps to delay the crack generation. The authors also use SEM and WCA to study the mechanism of crack delay and crack number reduction for round bamboo.
There is a list of things that the author should address and improve.
1. In section 2.4, the author should give more details about the experiment process.
2. It is hard to follow the quantitative analysis of the crack generation and development in section 3.2, including Fig. 6-8. The author should find another way to express the experiment results. For example. The average crack number/length for each treatment. The editors assigned to your paper ("Combination of polyethylene glycol impregnation and paraffin heat treatment to protect round bamboo from cracking") have now received comments from reviewers. We would like you to revise your paper in accordance with the referee and Associate Editor suggestions which can be found below (not including confidential reports to the Editor). Please note this decision does not guarantee eventual acceptance.
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Kind regards, Andrew Dunn Royal Society Open Science Editorial Office Royal Society Open Science openscience@royalsociety.org on behalf of Prof R. Kerry Rowe (Subject Editor) openscience@royalsociety.org Associate Editor's comments: Three reviewers have been sought for this paper. The editors have made their decision on the basis of the comments received, and recommend a major revision, as it is clear that the manuscript (while promising) has a number of areas that need improvement before it may be considered further. Please ensure that your revision not only identifies (in a comprehensive point-by-point response) all the changes made in response to the reviewer comments but also seek assistance from a language editing service (https://royalsociety.org/journals/authors/language-polishing/) to improve the standard of the written English -we sympathise that English is a tricky language, but the onus is on the authors to ensure that the quality of their scientific work is not obscured by the written language.

Comments to Author:
Reviewers' Comments to Author: Reviewer: 1 Comments to the Author(s) The inclination of cracking of round bamboo is a big issue to its application. This study tried to use a combination treatment of PEG and PH to solve this problem. The study is of practical value, while the manuscript needs to be improved in the following aspects: 1. The objectives as proposed in the introduction were not well proved. As suggested in introduction, PEG should penetrate the cell wall and then stabilize the bamboo, and paraffin heat treatment can avoid the leaching of PEG. For PEG penetration, the authors only gave the retention values of PEG, but no evidence of the PEG distribution in either cell wall or cell cavity. And this distribution can not be easily investigated by SEM observation. The authors should measure the change on thickness of bamboo culm after PEG and PEG-PH treatments, which might give some information on whether PEG entered cell wall or not.
For the effect of PH on leaching of PEG, the authors should compare the PEG retentions of PEG and PEG-PH treated samples after 26 weeks' exposure. 2. In "2.1 Materials", the authors should give more information on the sample preparation method, e.g., how many replicates are used? How the samples were selected and grouped to avoid the big deviations? From Fig.2, it seemed that the samples are quite different in cutting position, namely, the distance to the node. And I think this is quite important to the length of cracking. 3. In the line 2 in 2.3, "liquid paraffin" should be "melted paraffin"; 4. In 2.5, the authors used acetone in determination of PEG retention. What is the mechanism of this method? It should be briefly introduce so that the readers could understand. 5. In 2.7, the authors didn't mention how the samples were prepared. Is it carried out on the end surface or not? 6. In 3.1, "The loss of PEG was probably caused by the water soluble property and rinsing procedure during the leaching experiment." What is the leaching experiment? I didn't see any leaching experiment in this study. And also the Paragraph 2 in 3.1 seems no relation with the theme of 3.1. 7. In 3.4, the authors wrote "After treatment with PEG-PH, the cell wall became rough, with intercellular cavity filled and pits covered, which suggested that PEG can swell the cell wall. ". The logic in this sentence seems unreasonable. How can the rough cell wall and covered pits suggest the swelling cell wall by PEG? It needs to be revised. 8. The last sentence in 3.4, "The application of paraffin heat-treatment could enhance the resistance of PEG treated round bamboo from fungi by forming a hydrophobic surface protection." This sentence should be reconsidered. Because the types of fungi are so various, and PH can not always improve the fungal resistance. It would be better to find some references to support this conclusion.

Reviewer: 2
Comments to the Author(s) The manuscript is interesting and raises important issues regarding bamboo conservation. However, overall, the manuscript has to be scrutinized by a native English speaker.

Reviewer: 3
Comments to the Author(s) This paper uses the combination of PEG immersion and paraffin heating to solve the splitting problem for round bamboo. Compared with other existing processes, the method proposed in this paper helps to delay the crack generation. The authors also use SEM and WCA to study the mechanism of crack delay and crack number reduction for round bamboo.
There is a list of things that the author should address and improve.
1. In section 2.4, the author should give more details about the experiment process.
2. It is hard to follow the quantitative analysis of the crack generation and development in section 3.2, including Fig. 6-8. The author should find another way to express the experiment results. For example. The average crack number/length for each treatment.

Recommendation? Accept as is
Comments to the Author(s) It seems that the Authors corrected the most important drawbacks of the paper making it more clerr and easier to read.

Are the interpretations and conclusions justified by the results? Yes
Is the language acceptable? Yes

Do you have any ethical concerns with this paper? No
Have you any concerns about statistical analyses in this paper? No

Recommendation?
Accept as is

Comments to the Author(s)
The authors have addressed my previous comments very well. The manuscript can be published as is.

Review form: Reviewer 4
Is the manuscript scientifically sound in its present form? Yes

Recommendation? Accept with minor revision (please list in comments)
Comments to the Author(s) 2.1. four samples with one node, and the other two with two nodes， then is there any differences in cracking resistance between them?
will you please add the dynamic contact angle of bamboo treated with paraffin? just as figure 9. did. It will be much better to keep the comparisons consistent， and helpful to explain the cracking behaviors.

24-Sep-2019
Dear Miss Rao: On behalf of the Editors, I am pleased to inform you that your Manuscript RSOS-190105.R1 entitled "Combination of polyethylene glycol impregnation and paraffin heat treatment to protect round bamboo from cracking" has been accepted for publication in Royal Society Open Science subject to minor revision in accordance with the referee suggestions. Please find the referees' comments at the end of this email.
The reviewers and Subject Editor have recommended publication, but also suggest some minor revisions to your manuscript. Therefore, I invite you to respond to the comments and revise your manuscript.
• Ethics statement If your study uses humans or animals please include details of the ethical approval received, including the name of the committee that granted approval. For human studies please also detail whether informed consent was obtained. For field studies on animals please include details of all permissions, licences and/or approvals granted to carry out the fieldwork.
• Data accessibility It is a condition of publication that all supporting data are made available either as supplementary information or preferably in a suitable permanent repository. The data accessibility section should state where the article's supporting data can be accessed. This section should also include details, where possible of where to access other relevant research materials such as statistical tools, protocols, software etc can be accessed. If the data has been deposited in an external repository this section should list the database, accession number and link to the DOI for all data from the article that has been made publicly available. Data sets that have been deposited in an external repository and have a DOI should also be appropriately cited in the manuscript and included in the reference list.
If you wish to submit your supporting data or code to Dryad (http://datadryad.org/), or modify your current submission to dryad, please use the following link: http://datadryad.org/submit?journalID=RSOS&manu=RSOS-190105.R1 • Competing interests Please declare any financial or non-financial competing interests, or state that you have no competing interests.
• Authors' contributions All submissions, other than those with a single author, must include an Authors' Contributions section which individually lists the specific contribution of each author. The list of Authors should meet all of the following criteria; 1) substantial contributions to conception and design, or acquisition of data, or analysis and interpretation of data; 2) drafting the article or revising it critically for important intellectual content; and 3) final approval of the version to be published.
All contributors who do not meet all of these criteria should be included in the acknowledgements.
We suggest the following format: AB carried out the molecular lab work, participated in data analysis, carried out sequence alignments, participated in the design of the study and drafted the manuscript; CD carried out the statistical analyses; EF collected field data; GH conceived of the study, designed the study, coordinated the study and helped draft the manuscript. All authors gave final approval for publication.
• Acknowledgements Please acknowledge anyone who contributed to the study but did not meet the authorship criteria.
• Funding statement Please list the source of funding for each author.
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Once again, thank you for submitting your manuscript to Royal Society Open Science and I look forward to receiving your revision. If you have any questions at all, please do not hesitate to get in touch.
Kind regards, Andrew Dunn Royal Society Open Science Editorial Office Royal Society Open Science openscience@royalsociety.org on behalf of Prof R. Kerry Rowe (Subject Editor) openscience@royalsociety.org Associate Editor Comments to Author: A couple of minor queries remain from one of the reviewers, but otherwise this manuscript appears to be ready for acceptance. Please respond to the queries, and make changes required by the reviewers before resubmitting. Comments to the Author(s) 2.1. four samples with one node, and the other two with two nodes， then is there any differences in cracking resistance between them? 3.4 Figure 10. will you please add the dynamic contact angle of bamboo treated with paraffin? just as figure 9. did. It will be much better to keep the comparisons consistent， and helpful to explain the cracking behaviors.

Reviewer: 2
Comments to the Author(s) It seems that the Authors corrected the most important drawbacks of the paper making it more clerr and easier to read.

02-Oct-2019
Dear Miss Rao, I am pleased to inform you that your manuscript entitled "Combination of polyethylene glycol impregnation and paraffin heat treatment to protect round bamboo from cracking" is now accepted for publication in Royal Society Open Science.
You can expect to receive a proof of your article in the near future. Please contact the editorial office (openscience_proofs@royalsociety.org and openscience@royalsociety.org) to let us know if you are likely to be away from e-mail contact --if you are going to be away, please nominate a coauthor (if available) to manage the proofing process, and ensure they are copied into your email to the journal. Due to rapid publication and an extremely tight schedule, if comments are not received, your paper may experience a delay in publication.
Royal Society Open Science operates under a continuous publication model (http://bit.ly/cpFAQ). Your article will be published straight into the next open issue and this will be the final version of the paper. As such, it can be cited immediately by other researchers. As the issue version of your paper will be the only version to be published I would advise you to check your proofs thoroughly as changes cannot be made once the paper is published. Thank you very much for your email which you sent us the reviewer's report on our paper, we also wish to take this opportunity to thank the reviewer for constructive comments and valuable recommendations. We have studied the comments carefully and tried our best to revise the manuscript according to those good comments. Revised words are marked in red in the paper. The main corrections in the paper and the responds to the reviewer's comments are as follows: Response to Reviewer 1: 1. The objectives as proposed in the introduction were not well proved. As suggested in introduction, PEG should penetrate the cell wall and then stabilize the bamboo, and paraffin heat treatment can avoid the leaching of PEG. For PEG penetration, the authors only gave the retention values of PEG, but no evidence of the PEG distribution in either cell wall or cell cavity. And this distribution can not be easily investigated by SEM observation. The authors should measure the change on thickness of bamboo culm after PEG and PEG-PH treatments, which might give some information on whether PEG entered cell wall or not. Response: Thanks for your good suggestion. The material was fresh round bamboo that was in water saturated situation in this study. PEG permeated into bamboo by displacing the liquid moisture. It wasn't applicable to analyze the PEG distribution according to the change on thickness of bamboo culm. Therefore, we determined the amount of PEG in bamboo by extraction referring to the method from Kang et al. We also measure the change on thickness of bamboo culm after PEG and PEG-PH treatments by SEM, as figure11 shown. Comparing the SEM of untreated bamboo(a) with the PEG-PH treated one(b), the cell wall of the later swelled from 20 μm to 30 μm and the intercellular cavity disappeared, which indicated that PEG penetrated into the cell wall or cell cavity. 2. For the effect of PH on leaching of PEG, the authors should compare the PEG retentions of PEG and PEG-PH treated samples after 26 weeks' exposure. Response: Thanks for your suggestion, we will study the retention and leaching of PEG in our future experiments. In this paper, we focus on the effect of PEG and PEG-PH treatment in preventing round bamboo from cracking both in the treatment procedure and moistening/water-drying procedure, especially the latter.
The application of paraffin heat treatment after PEG immersion is to explore a suitable method for drying round bamboo. Round bamboo is lack in drying technology, nor having an advanced drying schedule like wood. The commonly adopt air drying procedure is not only time-consuming, but also cause lots of cracks. We have selected the best heating procedure from the preliminary experiments and applied in this paper.
The main aim of paraffin heat treatment was to dry round bamboo. The 3.2 section in resubmitted manuscript is to analysis if the paraffin heat treatment procedure caused the movement and loss of PEG during water evaporation. The results shown that PEG slightly lost after paraffin heat treatment. Additionally, the formation of paraffin coating on the surface of round bamboo in PEG-PH treatment provide hydrophobicity to bamboo, which prevent bamboo from water, as well as PEG from leaching. In our future researches, we will use cross-linking or chemical modification to prevent PEG from leaching out of round bamboo. We revised 3.2 section in revised manuscript, please check.
3.In "2.1 Materials", the authors should give more information on the sample preparation method, e.g., how many replicates are used? How the samples were selected and grouped to avoid the big deviations? From Fig.2, it seemed that the samples are quite different in cutting position, namely, the distance to the node. And I think this is quite important to the length of cracking. Response: Accepted. Indeed, the diameter and the number of the node would affect the length of cracking, we hadn't analyzed so comprehensive as reviewer said. We have added sample details in section 2.1. Please check. The sample details added were as follows: Freshly cut five-year old Phyllostachys iridescens was obtained from Anji, Zhejiang, China. The round bamboo with diameter of 42-61 mm was cut into specimens with a length of 300 mm. The average moisture content of the specimens was 58.3±5%, and six replicates were prepared for each treatment. To avoid large deviation in every group, the diameter of four samples were in the range of 42-50 mm with one node, and the other two were in 50-61 mm with two nodes at each end.