Renewable Tannin-Based Adhesive from Quebracho Extract and Furfural for Particleboards

Round 1

Reviewer 1 Report

  Several particleboards were produced using tannin-based resin as adhesive, instead of synthetic resins, and mechanical and physical properties of them were evaluated. Also, the characterization of the resin used were conducted. Production conditions (pressing temperature and time, the amount of the resin) were varied for examining better production condition. Overall experiments and analyzes were properly carried out and these results are logically presented. There are several papers dealing with similar topics using different sustainable and natural-based resins, however, few of such research conduct analyses other than physical and mechanical properties of the test boards. In this point, this manuscript will be especially beneficial to researchers in the field.

 

1           Regarding the 3^rd section title, isn’t it necessary to have either “Results and Discussion” or individual “Discussion”?

2           I would like to ask the authors to improve Tables and Figures. They are understandable, but the present version might not be easy for some. For examples: The lines and dots in Figure 2 are too thin and small, and the color difference is also small; For Figures 3, 5 and 6, it would be better if you add a simple explanation for readers who are unfamiliar with such plot at the beginning (what horizontal and vertical lines drawn with each box plot stand for); For Table 3, horizontal line added to separate the bottom three from above three might improve readers’ easy understanding.

3           How many test boards were made for each experimental condition (before sawing into test specimens)? Only one?

4           (I always feel this whenever I see analyses of SEM images.) For researchers (like me) who are not familiar with SEM images feel somewhat not totally convinced with the description and discussion presented. For one reason, this is because we cannot be certain about the image features which authors have mentioned, since their differences seem trivial. If there is an image only with particles (without resin) presented, it would greatly help understanding the features which authors had mentioned. Please consider, if possible.

5           Are there any possible explanation/hypotheses why there were not much difference in MOE and MOR regardless of production conditions, although the IB was clearly affected? If discussion on this point is added, it would make this manuscript more valuable and interesting.

6           Please closely check once more the manuscript. There are some unnecessary/missing word, period, and space, together with typos and unfamiliar expression. I also think the words “Table X” and “Figure X” cited in the main text should be capitalized.

Author Response

Answer to Reviewer 1

 

 Several particleboards were produced using tannin-based resin as adhesive, instead of synthetic resins, and mechanical and physical properties of them were evaluated. Also, the characterization of the resin used were conducted. Production conditions (pressing temperature and time, the amount of the resin) were varied for examining better production condition. Overall experiments and analyzes were properly carried out and these results are logically presented. There are several papers dealing with similar topics using different sustainable and natural-based resins, however, few of such research conduct analyses other than physical and mechanical properties of the test boards. In this point, this manuscript will be especially beneficial to researchers in the field.

• Regarding the 3^rdsection title, isn’t it necessary to have either “Results and Discussion” or individual “Discussion”?

Answer: Thank you for the observation. We agree with your suggestion in order to clarify what will be discussed in chapter 3. Thus, the title of chapter 3 has been modified in “Results and discussion”.

• I would like to ask the authors to improve Tables and Figures. They are understandable, but the present version might not be easy for some. For examples: The lines and dots in Figure 2 are too thin and small, and the color difference is also small; For Figures 3, 5 and 6, it would be better if you add a simple explanation for readers who are unfamiliar with such plot at the beginning (what horizontal and vertical lines drawn with each box plot stand for); For Table 3, horizontal line added to separate the bottom three from above three might improve readers’ easy understanding.

Answer: Thank you for the observation. We agree with your recommendations:

• Figure 2: we increased the thickness of line and dots and used different colours.
• Figure 3, 5, 6: We added the explanation of the plots in the caption of the figures.
• Table 3: In order to separate the new samples from the samples already discussed a bolder line wss added.
• How many test boards were made for each experimental condition (before sawing into test specimens)? Only one?

Answer: Two boards for each formulation and condition were pressed.

• (I always feel this whenever I see analyses of SEM images.) For researchers (like me) who are not familiar with SEM images feel somewhat not totally convinced with the description and discussion presented. For one reason, this is because we cannot be certain about the image features which authors have mentioned, since their differences seem trivial. If there is an image only with particles (without resin) presented, it would greatly help understanding the features which authors had mentioned. Please consider, if possible.

Answer: Again, I fully understand the observation of reviewer 1. We thought on taking some wood particle and do some measurement, but the high variability of particles (type, dimension, shape) would not have helped to detect any difference. Ideally, we could do the measurement of one particle and then resinate it. In this case maybe it could have helped, but the effect of pressing would have been lost. At present we have some difficulty to access the SEM again and therefore I please the reviewer to understand why we decided to keep this part without significant change.

• Are there any possible explanation/hypotheses why there were not much difference in MOE and MOR regardless of production conditions, although the IB was clearly affected? If discussion on this point is added, it would make this manuscript more valuable and interesting.

Answer: Thank you for this interesting observation, we tried to explain these results also considering other previous study proving the importance of the particle type for these properties (Line 35-361).

• Please closely check once more the manuscript. There are some unnecessary/missing word, period, and space, together with typos and unfamiliar expression. I also think the words “Table X” and “Figure X” cited in the main text should be capitalized.

Answer: Thank you for the observation. We went through the article again and we corrected/homogenized it as better as we can.

Author Response File: Author Response.docx

Reviewer 2 Report

General comments:

The article titled “Entirely renewable tannin-based adhesive for particleboard production” presents insightful knowledge on the evaluation of the potentiality of an entirely renewable tannin-based adhesive for particleboard production derived from industrial quebracho (Schinopsis balansae) tannin powder.

My general comments are:

·       The originality of the paper is high, with low similarity index to the published work.

·       The study is well documented, being in line with the guidelines for the authors, imposed by the journal.

·       The abstract is well presented, according to this research.

·       The state-of-the-art written in the introduction of the paper is well documented and focused on the actual research direction in the field.

·       The introduction presents properly the aim of the study.

·       The experimental procedure is justified but less comprehensive, specifically on the adhesives properties.

·       The results are presented in a concise manner, but low resolutions figures.

·       Furthermore, compared to references the results obtained are significant. The discussion section is clear, understandable and in accordance with the results obtained.

·       The conclusion is well written to conclude the results.

·       The reference format should be revised according to the journal requirements.

However, the article is lack of scientific soundness. Thus, the article can be considered after addressing the below comments in the revision (major revision).

 

Detail Comments:

1.     Title: The title seems correct, but it needs a bit revision. Please revise to “Tannin-Based Adhesive Derived from Industrial Grade Quebracho Tannin and Furfural for Particleboard”. Authors need to write the title specifically.

2.     Abstract:

a.      Page 1. Line 28-32. Authors should write the results of the adhesive properties briefly.

 3.       Introduction:

a.      Page 1. Line 40. We are now in 2022. Please update the wood composites market statistic from 2017 to 2021.

b.     Page 1. Please extend the introduction by including previous studies on the utilization of tannin as wood adhesives. I believe the following articles could be used as references to improve the manuscript:

·       Aristri, M. A., Lubis, M. A. R., Yadav, S. M., Antov, P., Papadopoulos, A. N., Pizzi, A., Fatriasari, W., Ismayati, M., & Iswanto, A. H. (2021). Recent Developments in Lignin- and Tannin-Based Non-Isocyanate Polyurethane Resins for Wood Adhesives—A Review. Applied Sciences, 11(9), 4242. https://doi.org/10.3390/app11094242

·       Aristri, M. A., Lubis, M. A. R., Iswanto, A. H., Fatriasari, W., Sari, R. K., Antov, P., Gajtanska, M., Papadopoulos, A. N., & Pizzi, A. (2021). Bio-Based Polyurethane Resins Derived from Tannin: Source, Synthesis, Characterisation, and Application. Forests, 12(11), 1516. https://doi.org/10.3390/f12111516

c.      Page 1. Line 101. The characterisation of the tannin-based adhesive is not comprehensive. Please determine the resin’s solids content, the pH, the functional groups of the adhesive before and after curing using FTIR, and the curing temperature of the adhesive using DSC.

4.        Material and methods:

a.      Page 3. Line 107. Please write the concentration of Furfural specifically.

b.     Page 3, Line 112-113. Please write the specific wood species. Or you can write mix wood species.

c.      Page 3, Line 147. Please write the full name of MW >> molecular weight (MW).

d.     Page 4, Line 152. Please write the specific condition of the following methods:

·       What is the temperature of Quebracho tannin water solution was prepared at 45 % w/w.

·       What is the temperature during the furfural addition.

·       Based on what is the addition of furfural? Is it based on tannin solids content? Please write it.

·       When is the reaction between tannin and furfural finish? Please write it in detail.

e.      Page 4, Line 156. How do you know the gelation will be occurred at 100°C? To justify this, you need to measure the curing temperature using DSC. Or you need to write the published methods which used tannin and furfural.

f.      Page 4, Line 161. Is it rotational speed or shear rate? The unit of rotational speed is RPM, while the unit of shear rate is s^–1.

g.     Page 4, Line 162. You need to determine the resin’s solids content, the pH, the functional groups of the adhesive before and after curing using FTIR, and the curing temperature of the adhesive using DSC.

h.     Page 4, Line 163. Please write the combination pressing time, temperature, and adhesive content in the methods. It is important. It is not acceptable without a detail experimental design.

 

5.       Results and discussion:

a.      Page 5, Line 219. The curing kinetics cannot be determined using gel time analysis. You have to performed DSC and DMA analysis to investigate the curing kinetics. Revise this.

b.     Page 6, Figure 2. Revise the figure with higher resolution of 1200 DPI. In addition, make sure the unit. In the method you wrote ‘Rotational Speed’, but in the Figure you wrote “shear rate”. Revise this.

c.      Page 6. Figure 2. You have to explain why the viscosity decreased with the addition of furfural as a function of shear rate.

d.     Page 7, Figure 4. Revise the figure with higher resolution of 1200 DPI.

e.      Page 7. Line 255-257. Please combine into one paragraph.

f.      Page 8, Figure 5. Revise the figure with higher resolution of 1200 DPI.

g.     Page 8, Figure 5. Why did you select 160, 180, and 200°C of pressing temperature. Please explain it in the methods section.

h.     Page 9, Figure 7. Revise the figure with higher resolution of 1200 DPI.

 

6.     Conclusions

a.      Please write the detail of the Experimental Designs (combination of pressing, temperature, and adhesive content) in the methods section. It is not acceptable when authors wrote “In this work the efficacy of quebracho tannin-furfural adhesive for particleboards was studied modifying pressing temperature, pressing time so as adhesive content”.

Author Response

Answer to Reviewer 2

 

The article titled “Entirely renewable tannin-based adhesive for particleboard production” presents insightful knowledge on the evaluation of the potentiality of an entirely renewable tannin-based adhesive for particleboard production derived from industrial quebracho (Schinopsis balansae) tannin powder.

My general comments are:

• The originality of the paper is high, with low similarity index to the published work.
• The study is well documented, being in line with the guidelines for the authors, imposed by the journal.
• The abstract is well presented, according to this research.
• The state-of-the-art written in the introduction of the paper is well documented and focused on the actual research direction in the field.
• The introduction presents properly the aim of the study.
• The experimental procedure is justified but less comprehensive, specifically on the adhesives properties.
• The results are presented in a concise manner, but low resolutions figures.
• Furthermore, compared to references the results obtained are significant. The discussion section is clear, understandable and in accordance with the results obtained.
• The conclusion is well written to conclude the results.
• The reference format should be revised according to the journal requirements.

Answer: Thank you very much for the nice systematic overview. We realized that the quality of figures was poor and we modified them to render them easier to read.

However, the article is lack of scientific soundness. Thus, the article can be considered after addressing the below comments in the revision (major revision).

 

Detail Comments:

1. Title: The title seems correct, but it needs a bit revision. Please revise to “Tannin-Based Adhesive Derived from Industrial Grade Quebracho Tannin and Furfural for Particleboard”. Authors need to write the title specifically.

Answer: Thank you very much for your suggestion. We also had the sensation the title could have been improved. We took part of your suggestion and propose another article.

2. Abstract:
3. Page 1. Line 28-32. Authors should write the results of the adhesive properties briefly.

Answer: Thank you for the comments, we have added in the abstract the results of mechanical properties for the panels that highlighted higher values. (Line 32-34)

3. Introduction:
4. Page 1. Line 40. We are now in 2022. Please update the wood composites market statistic from 2017 to 2021.

Answer: Thanks for the suggestion. We have tried to look for more recent data and we found some in the FAO website but we don’t know how reliable are them, because they consider also the period of covid and hence they are more contained (despite in the same order of magnitude). For this reason we rather prefer to keep the published document.

1. Page 1. Please extend the introduction by including previous studies on the utilization of tannin as wood adhesives. I believe the following articles could be used as references to improve the manuscript:

• Aristri, M. A., Lubis, M. A. R., Yadav, S. M., Antov, P., Papadopoulos, A. N., Pizzi, A., Fatriasari, W., Ismayati, M., & Iswanto, A. H. (2021). Recent Developments in Lignin- and Tannin-Based Non-Isocyanate Polyurethane Resins for Wood Adhesives—A Review. Applied Sciences, 11(9), 4242. https://doi.org/10.3390/app11094242
• Aristri, M. A., Lubis, M. A. R., Iswanto, A. H., Fatriasari, W., Sari, R. K., Antov, P., Gajtanska, M., Papadopoulos, A. N., & Pizzi, A. (2021). Bio-Based Polyurethane Resins Derived from Tannin: Source, Synthesis, Characterisation, and Application. Forests, 12(11), 1516. https://doi.org/10.3390/f12111516

Answer: we consider that the proposed studies are  in line with the research topic, and hence we added them in the introduction. (Line 75-78, 84-86)

1. Page 1. Line 101. The characterisation of the tannin-based adhesive is not comprehensive. Please determine the resin’s solids content, the pH, the functional groups of the adhesive before and after curing using FTIR, and the curing temperature of the adhesive using DSC.

Answer: Regarding the pH we stated it in the experimental section. The solid content of the resin is intrinsically reported considering the amount of tannin and furfural as the part which turns solid after curing. Measuring it at lower temperature, it may bring to lost of furfural that could partially evaporate before curing. The FT-IR study on this resin was already presented in a previous study of our group, which we cited already. The DSC is also an important tool, but we observed a dominant peak of water evaporation at around 100°C which cover any other reaction signal.

4. Material and methods:
5. Page 3. Line 107. Please write the concentration of Furfural specifically.

Answer: We specified the concentration of furfural. (Line 113)

b.Page 3, Line 112-113. Please write the specific wood species. Or you can write mix wood species.

Answer: Thank you for the comment, we modified in order to specify the wood species. (Line 119)

c.Page 3, Line 147. Please write the full name of MW >> molecular weight (MW).

Answer: We explained it (Line 153)

d.Page 4, Line 152. Please write the specific condition of the following methods:

• What is the temperature of Quebracho tannin water solution was prepared at 45 % w/w.

Answer: We added this part in line 158

• What is the temperature during the furfural addition.

Answer: We specified the temperature before, the temperature at which furfural is added, without further specification, is understood to be the previous one.

• Based on what is the addition of furfural? Is it based on tannin solids content? Please write it.

Answer: We specified it previously

       When is the reaction between tannin and furfural finish? Please write it in detail.

Answer: This question is unclear. It’s impossible to know when the reaction is completely finished. It will depend on temperature and reaction conditions. We suppose that in the press conditions (in presence of particles) when the process is optimized (e.g.160°C, 11 min) the polymer is cured… Harsher conditions may already involve some degradation.

Page 4, Line 156. How do you know the gelation will be occurred at 100°C? To justify this, you need to measure the curing temperature using DSC. Or you need to write the published methods which used tannin and furfural.

Answer: Thank you for the observation. Certainly, much more information on reaction kinetics can be obtained through thermal DSC analysis. But not being able to perform the same technique, equally interesting information can be obtained through the gel time test for adhesive formulations. We have added the reference describing the methodology. (Line 164, ref 48)

161. Page 4, Line 161. Is it rotational speed or shear rate? The unit of rotational speed is RPM, while the unit of shear rate is s^–1.

Answer: Thank you for the comments, we corrected the mistake.  

162. Page 4, Line 162. You need to determine the resin’s solids content, the pH, the functional groups of the adhesive before and after curing using FTIR, and the curing temperature of the adhesive using DSC.

Answer: We understood the point and we answered already at point 3c.

163. Page 4, Line 163. Please write the combination pressing time, temperature, and adhesive content in the methods. It is important. It is not acceptable without a detail experimental design.

 Answer: Ok, we added it.

5. Results and discussion:
6. Page 5, Line 219. The curing kinetics cannot be determined using gel time analysis. You have to performed DSC and DMA analysis to investigate the curing kinetics. Revise this.

 Answer: Ok, we understand the point, hence we have modified the sentence using “reactivity” instead of “ curing kinetics” (Line 229).

2. Page 6, Figure 2. Revise the figure with higher resolution of 1200 DPI. In addition, make sure the unit. In the method you wrote ‘Rotational Speed’, but in the Figure you wrote “shear rate”. Revise this.

 Answer: Thank you for the comment, we have increased the resolution of figure 2. In addition, as explaining in 4f reply “share rate” is now corrected.

6. Page 6. Figure 2. You have to explain why the viscosity decreased with the addition of furfural as a function of shear rate.

 Answer: Ok. We modified the sentence, describing the decrease of viscosity too (Line 225-227).

4. Page 7, Figure 4. Revise the figure with higher resolution of 1200 DPI.

Answer: Ok. We replaced the former figure with a higher resolution one

7. Page 7. Line 255-257. Please combine into one paragraph.

Answer: Ok.

5. Page 8, Figure 5. Revise the figure with higher resolution of 1200 DPI.

Answer: Ok. We replaced the former figure with a higher resolution one

5. Page 8, Figure 5. Why did you select 160, 180, and 200°C of pressing temperature. Please explain it in the methods section.

Answer: Thank you we reviewed 2.4 chapter adding the missed information highlighted (Line 173-185)

7. Page 9, Figure 7. Revise the figure with higher resolution of 1200 DPI.

Answer: Ok. Done.

6. Conclusions
7. Please write the detail of the Experimental Designs (combination of pressing, temperature, and adhesive content) in the methods section. It is not acceptable when authors wrote “In this work the efficacy of quebracho tannin-furfural adhesive for particleboards was studied modifying pressing temperature, pressing time so as adhesive content”.

Answer: Ok, we reviewed the entire conclusions chapter ( Line 408-422)

 

Author Response File: Author Response.docx

Reviewer 3 Report

 

The study has scientific merit. However, the manuscript is not well-written. Extensive modification is required, especially the grammar. From my point of view, the characterization of tannin is insufficient. It is beneficial if TGA and FTIR can be added. Also, formaldehyde emission of samples was not presented. Please consider.

Introduction – Can the author separate it to a few paragraphs?

Line 40 – “Moreover, in order to limit the CO2 emissions the current growth foresees a wood composites output of around 658.1 million m3 by 2027” – I do not understand this sentence, what has the limitation on CO2 emission to do with wood composite output? The author should elaborate.

Line 50 -  what do you mean by “contained cost”?

Line 51-53 – “Within…. consumption” The whole sentence is confusing, kindly revise.

Line 83 – two indeed, please remove one.

The whole introduction section requires extensive modifications. There are many weird expressions and hanging sentences.

Line 168 – “Three pressing times and temperatures”, please mention the times and temperatures used here. What is the target final thickness of the boards?

Table 1 – how many samples were tested? Why the standard deviation for PS is so high (552±103)? Is the results reliable?

Line 218 – “Conversely, the addition of furfural involved a lower drop as the shear stress increases (light blue curve)” Please clarify this sentence.

The gel time of the tannin adhesive was 304 s, around 5 min at 100 °C, but why the authors chose to use longer pressing time of 7, 9 and 11 min at higher temperature?

Line 222 – “Usually phenol-formaldehyde resins present slower kinetics than UF’s and when condensed tannin are added the crosslinking occur 30% faster” what do you mean by this?

Line 223 – “This means that applying exclusively tannin as phenolic constituent allow to exploit also the slower, but bio-based furfural, as hardener with good processability.” This statement is also very confusing.

Line 237 – “Actually, the pre-pressing at 9 mm could have caused the observed thickness decrease because the rigidity of tannin-furanic adhesives [57] does not allow the expected spring-back.” What do you mean?

Figure 4 – can you provide a figure with higher resolution?

Can you please provide more discussion on the influence of pressing temperature and time on density and density profile? What combination is the optimum?

Line 266 – full stop is missing

For all the properties of the particleboard, do you have control board for comparison?

Figure 7 is too low in resolution

Line 313 – “The most promising series at 160°C with lower pressing time (in italic)”. Why not boards that pressed at 13 min and 15% adhesive? It has better IB, MOR, MOE and TS.

Section 3.4 – can you make a Table to compare the results from previous literatures?

Please relate the characteristics of tannin adhesive as well as the density profile with the properties of the produced particleboard.

Author Response

Reviewer 3

 

The study has scientific merit. However, the manuscript is not well-written. Extensive modification is required, especially the grammar. From my point of view, the characterization of tannin is insufficient. It is beneficial if TGA and FTIR can be added. Also, formaldehyde emission of samples was not presented. Please consider

Answer: Thank you for your review. We have corrected the paper according to your suggestions. For the three analysis requested we report that:

• The FT-IR study on this resin was already presented in a previous study of our group, which we cited already.
• The DSC is also an important tool, but we observed a dominant peak of water evaporation at around 100°C which cover any other reaction signal.
• The formaldehyde emission test would be interesting, but also not really congruent because neither tannin nor furfural emit formaldehyde, meaning the emission will be due to wood.

Introduction – Can the author separate it to a few paragraphs?

Answer: Thank you for the suggestion, we have added a part of part and we organized the introduction in several paragraphs.

Line 40 – “Moreover, in order to limit the CO2 emissions the current growth foresees a wood composites output of around 658.1 million m3 by 2027” – I do not understand this sentence, what has the limitation on CO2 emission to do with wood composite output? The author should elaborate.

Answer: Sentence reviewed  (Line 42-44)

Line 50 -  what do you mean by “contained cost”?

Answer: When we report contained costs, we mean “low” costs.

Line 51-53 – “Within…. consumption” The whole sentence is confusing, kindly revise.

Answer: Thank you for the observation. We revised the sentence.

Line 83 – two indeed, please remove one.

Answer: One was removed.

The whole introduction section requires extensive modifications. There are many weird expressions and hanging sentences.

Answer: Thank you for the suggestion. We went through the whole introduction and we realized that some part could have been improved.

Line 168 – “Three pressing times and temperatures”, please mention the times and temperatures used here. What is the target final thickness of the boards?

Answer: Thank you for the comment, we add the missed information (Line 176-178).

Table 1 – how many samples were tested? Why the standard deviation for PS is so high (552±103)? Is the results reliable?

Answer: yes, the result is reliable because we measured three times.

Line 218 – “Conversely, the addition of furfural involved a lower drop as the shear stress increases (light blue curve)” Please clarify this sentence.

Answer: We have modified the sentence, clarifying also the decrease of the viscosity. (Line 227-229)

The gel time of the tannin adhesive was 304 s, around 5 min at 100 °C, but why the authors chose to use longer pressing time of 7, 9 and 11 min at higher temperature?

Answer: Yes, Gel time could be defined as the time it takes for a mixed resin system to gel or become so highly viscous that it can no longer be considered workable or able to be handled. And it is an usefully parameter to characterize and compare different adhesives. The hardening temperature/time request to press a stable board are different compered to the gel time. Lower temperature have been tried (140°C, table 3) too, but lower mechanical properties have been found.

Line 222 – “Usually phenol-formaldehyde resins present slower kinetics than UF’s and when condensed tannin are added the crosslinking occur 30% faster” what do you mean by this?

Answer: Thank you for your comment. We reported the comparison between UF and PF synthetic resins, explaining what are the typical gelling time of those adhesive system. We reviewed the paragraph in order to lead a better comprehension. (Line 233-238)

Line 223 – “This means that applying exclusively tannin as phenolic constituent allow to exploit also the slower, but bio-based furfural, as hardener with good processability.” This statement is also very confusing.

Answer: See previous reply

Line 237 – “Actually, the pre-pressing at 9 mm could have caused the observed thickness decrease because the rigidity of tannin-furanic adhesives [57] does not allow the expected spring-back.” What do you mean?

Answer: Ok, the final thickness of 1 cm may not have been achieved due to the pre-pressing at 0.9 cm and the known stiffness of tannin resins.

Figure 4 – can you provide a figure with higher resolution?

Answer: Done

Can you please provide more discussion on the influence of pressing temperature and time on density and density profile? What combination is the optimum?

Answer: Thank you for the comment, we added a one more sentence to clarify output from the density profile analysis. (Lines 262- 264)

Line 266 – full stop is missing

Answer: Added

For all the properties of the particleboard, do you have control board for comparison?

Answer: We have done an in depth bibliographic resource to compare our results with as the main adhesive proposed in the literature as well with the European standard requirements.

Figure 7 is too low in resolution

Answer: Changed

Line 313 – “The most promising series at 160°C with lower pressing time (in italic)”. Why not boards that pressed at 13 min and 15% adhesive? It has better IB, MOR, MOE and TS.

Answer: The panels pressed at 13 min reported slightly higher MOE (1560), MOR (5.5) and slightly lower TS (77) respect the panel pressed at 11 min, but this increase not allow to satisfy higher class of European standards. Thus, using less pressing time could be more suitable from an energy point of view.  

Section 3.4 – can you make a Table to compare the results from previous literatures?

Answer: Absolutely, can be very interesting having a in depth bibliographic review grouped in the table, but the aim of the current work is to propose a new appealing bio-formulation, selecting just the most recent work as a “references”.  In order to do a proper job of comparing various formulations in this field, revision work would be needed. So, we decide to add a extensive discussion about the comparison with previous results, focalising the tables and figures with the results obtained in our work.

Please relate the characteristics of tannin adhesive as well as the density profile with the properties of the produced particleboard.

Answer: As said in the reply before, we add a clarification of the density profile influence (Lines 262- 264). Furthermore, a more explanation has been put in the conclusions (Line 419-420)

 

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The manuscript has been revised accordingly and it's been improved significantly.

It is now suitable for the publication in Forests.

Reviewer 3 Report

The paper has been improved and it's understandable that some recommended experiments was unable to carried out. the paper can be accepted at present form.