Selected Physical and Mechanical Properties of Microwave Heat Treated Rubberwood (Hevea brasiliensis)
, Jitralada Kittijaruwattana 1, Emilia-Adela Salca 2 and Salim Hiziroglu 3,*Round 1
Reviewer 1 Report
The topic of the paper is within the scope of the Applied Sciences journal and might be interesting to the readers. However, the manuscript contains some shortcomings, as follows:
- In the Introduction the authors presented the influence of thermal treatment on physical and mechanical properties of wood. In my opinion, chemical changes, and their impact on physical and mechanical properties during this process should be explained, e.g.:
- http://dx.doi.org/10.1016/j.biortech.2013.06.110
- https://doi.org/10.1007/s13595-016-0541-x
- https://ojs.cnr.ncsu.edu/index.php/BioRes/article/view/BioRes_03_2_Kocaefe_PB_ThermalTreatment_Birch_Aspen
- Please, change hemicellulose to hemicelluloses throughout the whole manuscript.
- Lines 99-100. How were temperatures of 150, 180, and 220 °C reached? Please, explain this in more details.
- Lines 202-208. FTIR spectroscopy is the main drawback of this manuscript. In the Fig. 4 caption authors declare “shows the intensity of the peak absorbance”, however in the Fig. 4 shows transmittance. I do not agree with the statement “The amount of functional groups in untreated and heat treated rubberwood was illustrated in Figure 4”. Fig. 4 represents only spectra and absorbance intensities must be calculated for the quantification. Please, explain the source of C-N and C-Br groups in rubberwood. Discussion in this section is missing (comparison with other authors, e.g. https://doi.org/10.1007/s10086-018-1721-0 ; https://doi.org/10.1016/j.molstruc.2012.08.035 ). You must also explain and discuss changes in typical wood functional groups (e.g. hydroxyl, acetyl, methoxyl), and lignin structural units – syringyl, guaiacyl, etc. This part must be completely rewritten.
- Line 241. Reference 7. Change Pavlo B. to Bekhta, P. (Pavlo is the first name, Bekhta is the surname) and check the title of this paper https://doi.org/10.1515/HF.2003.080 .
Author Response
MEMORANDUM
DATE : August 22, 2020
TO: Aria Tang, Applied Science, MDPI
FROM: Salim Hiziroglu Article applsci-913671
SUBJECT : Article applsci-913671, Responses to the reviewers’ comments
Reviewer #1
COPY : A. Chotikhun, J. Kittijaruwattana, E. Salca.
All corrections in the manuscript was highlighted in yellow color. Overall language, grammar errors as well as spelling mistakes in the manuscript were also revised to its new format.
The topic of the paper is within the scope of the Applied Sciences journal and might be interesting to the readers. However, the manuscript contains some shortcomings, as follows:
- In the Introduction the authors presented the influence of thermal treatment on physical and mechanical properties of wood. In my opinion, chemical changes, and their impact on physical and mechanical properties during this process should be explained, e.g.:
- http://dx.doi.org/10.1016/j.biortech.2013.06.110
- https://doi.org/10.1007/s13595-016-0541-x
- https://ojs.cnr.ncsu.edu/index.php/BioRes/article/view/BioRes_03_2_Kocaefe_PB_ThermalTreatment_Birch_Aspen
Five new references were added and cited in the manuscript accordingly. Some new material related to influence of heat treatment was also included into the revised manuscript.
- Please, change hemicellulose to hemicelluloses throughout the whole manuscript.
Necessary correction was done throughout the text.
- Lines 99-100. How were temperatures of 150, 180, and 220 °C reached? Please, explain this in more details.
The samples of rubberwood were treated in the microwave system at the temperature levels of 150°C, 180°C, and 220°C for 20 min. by using a software Arduino 1.8.7. which controlled temperature levels in the microwave oven at an accuracy level of 4oC. Thermocouples were also used to measure the actual temperature in the microwave reactor.
Above statement was added in revised manuscript.
Lines 202-208. FTIR spectroscopy is the main drawback of this manuscript. In the Fig. 4 caption authors declare “shows the intensity of the Hemi
- peak absorbance”, however in the Fig. 4 shows transmittance. I do not agree with the statement “The amount of functional groups in untreated and heat treated rubberwood was illustrated in Figure 4”. Fig. 4 represents only spectra and absorbance intensities must be calculated for the quantification. Please, explain the source of C-N and C-Br groups in rubberwood. Discussion in this section is missing (comparison with other authors, e.g. https://doi.org/10.1007/s10086-018-1721-0 ; https://doi.org/10.1016/j.molstruc.2012.08.035 ). You must also explain and discuss changes in typical wood functional groups (e.g. hydroxyl, acetyl, methoxyl), and lignin structural units – syringyl, guaiacyl, etc. This part must be completely rewritten.
Based on with extended discussion with the principal author and co-authors it was the decision to eliminate material related to FTIR part of the current work from the manuscript at this time. I was told that there are more data related to FTIR and some other chemical analysis of the work and they will be used in detail in a future publication.
- Line 241. Reference 7. Change Pavlo B. to Bekhta, P. (Pavlo is the first name, Bekhta is the surname) and check the title of this paper https://doi.org/10.1515/HF.2003.080 .
Name related to the reference was corrected.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Introduction:
Introduction is inconsistent - a little bit of temperature (impact) - a little bit of softwoods - a little bit of hardwoods etc.
Focus on hardwood - temperature impact and time of temperature application - this is most crucial, as microwave modifications operates with short application time. Modification effect is a multivariate result of moisture content - temperture level and operation time. This has to be reviewed in the introduction in order to analyse the results.
Method: Monitoring temperature level during operation (or in operation breaks) is crusial in order to achieve and redord the proper temperature - this should be better described in item 2: Materials and methods.
Different results are presented with two or three digits after the decimal point: e.g MOE 6,280.21 N/mm² of MOR 107.11 N/mm², Swelling 1,601% - I doubt, that these digits represent achievable accuracy!!
Fig. 2 - indicate the cracks etc. in fig. 2b
Short operation time (temperture impact) and modification effects are interconnected - this has to be discussed - shorter time - higher temperature - counterbalancing the the modification effect - wood degradation?
The comparison of reference values and indicators of the modification effect (and/or the material degradation) are chosen more of less randomly. Specific indicatars (density, MOR, MOE, hardness) should be followed consistent.
Author Response
MEMORANDUM
DATE : August 22, 2020
TO: Aria Tang, Applied Science, MDPI
FROM: Salim Hiziroglu Article applsci-913671
SUBJECT : Article applsci-913671, Responses to the reviewers’ comments
Reviewer #2
COPY : A. Chotikhun, J. Kittijaruwattana, E. Salca.
All corrections in the manuscript were highlighted in yellow color. Overall language, grammar errors as well as spelling mistakes in the manuscript were also revised to its new format.
Introduction is inconsistent - a little bit of temperature (impact) - a little bit of softwoods - a little bit of hardwoods etc.
Focus on hardwood - temperature impact and time of temperature application - this is most crucial, as microwave modifications operates with short application time. Modification effect is a multivariate result of moisture content - temperature level and operation time. This has to be reviewed in the introduction in order to analyse the results.
Introduction was revised to its new format. Some statements including following one related various aspects of heat treatment influence on wood was also added and highlighted within the text.
During the heat treatment of wood , density, anatomical structure and units size are some of the parameters influencing overall quality of the process. Application of microwave heat treatment would be ideal for species having less permeability such as oak or maple. It is clear that low permeable species will simply resist heat transfer during the treatment resulting in longer processing time. This would also create certain amount of excessive discoloration on the samples especially when higher temperature levels are used. In the case of rubberwood being as relatively porous hardwood species used in this work, reducing heat exposure time in a microwave would be considered as a main advantage. Such advantage will not only create overall lower energy consumption but also complete the process within a short period of time without having any possible defects.
Method: Monitoring temperature level during operation (or in operation breaks) is crusial in order to achieve and redord the proper temperature - this should be better described in item 2: Materials and methods.
The samples of rubberwood were treated in the microwave system at the temperature
Temperature levels of 150°C, 180°C, and 220°C for 20 min. by using a software Arduino 1.8.7. which controlled temperatures in the microwave oven at an accuracy level of 4oC. Thermocouples were also used to measure the actual temperature in the microwave reactor.
Different results are presented with two or three digits after the decimal point: e.g MOE 6,280.21 N/mm² of MOR 107.11 N/mm², Swelling 1,601% - I doubt, that these digits represent achievable accuracy!!
Fig. 2 - indicate the cracks etc. in fig. 2b
Short operation time (temperture impact) and modification effects are interconnected - this has to be discussed - shorter time - higher temperature - counterbalancing the the modification effect - wood degradation?
MOE, MOR, and dimensional stability values of the samples were revised by deleting digits as suggested by the reviewer. Tables were also revised accordingly.
The comparison of reference values and indicators of the modification effect (and/or the material degradation) are chosen more of less randomly. Specific indicatars (density, MOR, MOE, hardness) should be followed consistent.
Yes we agree with this comment and we believe all properties of the treated samples are presented within an order having a consistency in revised manuscript.
Author Response File: Author Response.pdf
Reviewer 3 Report
The study concerns the physical and mechanical properties of rubber wood heat-treated in a microwave oven. Three temperature levels (150°C, 180°C and 220°C) are taken into account. The modulus of elasticity, modulus of rupture and hardness of the samples were tested as well as the dimensional stability (swelling) and water absorption. This is a study of great interest to the wood drying industry.
So, reviewing the document leads to the following observations:
- I advocate authors to slightly change the title of the manuscript as follows: “Mechanical and physical properties of Microwave Heat Treated Rubberwood (Hevea brasiliensis)
- In the introduction, highlight some references on modeling anisotropic microwave heating of wood. As an example, the following reference:3D numerical analysis of the thermal effect and dielectric anisotropy on thawing frozen wood using microwave energy . International Journal of Thermal Sciences (2015), 89: 58-78.
- I recommend that authors add in the manuscript (section: Materials and methods): - Frequency of the microwaves used and, if possible, introduce the electrical properties of Heva wood.
- I would like the authors to clearly point out the limitations of the experimental approach used in the study.
From what has been stated, the current manuscript may possibly be published in the Applied Sciences Journal, if authors are willing to carefully perform the aforementioned comments and queries.
Author Response
MEMORANDUM
DATE : August 22, 2020
TO: Aria Tang, Applied Science, MDPI
FROM: Salim Hiziroglu Article applsci-913671
SUBJECT : Article applsci-913671, Responses to the reviewers’ comments
Reviewer #3
COPY : A. Chotikhun, J. Kittijaruwattana, E. Salca.
All corrections in the manuscript were highlighted in yellow color. Overall language, grammar errors as well as spelling mistakes in the manuscript were also revised to its new format.
The study concerns the physical and mechanical properties of rubber wood heat-treated in a microwave oven. Three temperature levels (150°C, 180°C and 220°C) are taken into account. The modulus of elasticity, modulus of rupture and hardness of the samples were tested as well as the dimensional stability (swelling) and water absorption. This is a study of great interest to the wood drying industry.
So, reviewing the document leads to the following observations:
- I advocate authors to slightly change the title of the manuscript as follows: “Mechanical and physical properties of Microwave Heat Treated Rubberwood (Hevea brasiliensis)
As suggested title was changed to “Selected Physical and Mechanical Properties of Microwave Heat Treated Rubberwood (Hevea brasiliensis)”
- In the introduction, highlight some references on modeling anisotropic microwave heating of wood. As an example, the following reference:3D numerical analysis of the thermal effect and dielectric anisotropy on thawing frozen wood using microwave energy . International Journal of Thermal Sciences (2015), 89: 58-78.
Yes,we agree with the reviewer and we looked at suggested article by F.
Erchiqui, Z. Annasabi M.Souli and F. Slauui-Hasnaoui. But I am afraid this work
is dealing with mostly frozen wood at advanced theoretical level beyond the
perspective of our experimental work. Therefore we would like to take liberty not
to cite this work at this time but we are definitely planning to use it in the second
phase of our study in near future.
- I recommend that authors add in the manuscript (section: Materials and methods): - Frequency of the microwaves used and, if possible, introduce the electrical properties of Heva wood.
Frequency value of the microwave used was added in the revised manuscript.
- I would like the authors to clearly point out the limitations of the experimental approach used in the study.
Major limitation of experimental approach used in this work is adverse influence on mechanical properties of the samples which was added into the text at various places such as below statement in Conclusion
“Microscopic evaluation of the specimens revealed that certain amount of damage
took place at cellwall level.”
From what has been stated, the current manuscript may possibly be published in the Applied Sciences Journal, if authors are willing to carefully perform the aforementioned comments and queries.
Reviewer 4 Report
The work concerns an interesting topic and is methodically performed correctly. However, it requires editorial correction. In the list of literature in item 7 is Pavlo B., and should be Bekhta P. I ask the authors to check the remaining items. Moreover, the conclusions need to be rewritten, in this form they are not readable.
Author Response
MEMORANDUM
DATE : August 22, 2020
TO: Aria Tang, Applied Science, MDPI
FROM: Salim Hiziroglu Article applsci-913671
SUBJECT : Article applsci-913671, Responses to the reviewers’ comments
Reviewer #4
COPY : A. Chotikhun, J. Kittijaruwattana, E. Salca.
All corrections in the manuscript were highlighted in yellow color. Overall language, grammar errors as well as spelling mistakes in the manuscript were also revised to its new format.
Comments and Suggestions for Authors
The work concerns an interesting topic and is methodically performed correctly. However, it requires editorial correction. In the list of literature in item 7 is Pavlo B., and should be Bekhta P. I ask the authors to check the remaining items. Moreover, the conclusions need to be rewritten, in this form they are not readable.
Reference related P.Bekhta was corrected.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
My suggestions have been accepted. In my opinion, the manuscript is now ready for publication in its present form.
Author Response
Thanks
Salim Hiziroglu
